Interfaces and Inter Phases in Multi Component Materials

EUROPEAN

European Polymer Journal 41 (2005) 645–662

www.elsevier.com/locate/europolj

POLYMERJOURNAL

Review

Interfaces and interphases in multicomponent materials:past, present, future

Bela Pukanszky a,b,*

a Department of Plastics and Rubber Technology, Budapest University of Technology and Economics, P.O. Box 91,

H-1521 Budapest, Hungaryb Institute of Materials and Environmental Chemistry, Chemical Research Center, Hungarian Academy of Sciences, P.O. Box 17,

H-1525 Budapest, Hungary

Received 7 February 2004; accepted 27 October 2004

Abstract

Interfacial interactions and interphases play a key role in all multicomponent materials irrespectively of the number

and type of their components or their actual structure. They are equally important in particulate filled polymer, polymer

blends, fiber reinforced advanced composites, nanocomposites or biomimetic materials. Recognition of the role of the

main factors influencing interfacial adhesion and proper surface modification may lead to significant progress in many

fields of research and development, as well as in related technologies. Although the role and importance of interfaces and

interphases are the same for all multicomponent materials, surface modification must be always selected according to the

objectives targeted, as well as to the characteristics of the particular system. Efficient surface treatment or coupling alone

might not achieve the desired goal, we must always keep in mind that an interphase forms always in such materials and

the control of interphase properties must be part of the modification philosophy. The use of multiphase, multicomponent

materials is expected to grow with a larger than average rate also in the future. It is important to keep the interdisciplin-

ary nature of the area, since principles and techniques developed by one field may find application also in other areas.

� 2004 Elsevier Ltd. All rights reserved.

Keywords: Interfacial interactions; Multicomponent materials; Heterogeneous structure; Surface modification; Polymer blends;

Particulate filled polymers; Fiber reinforced composites; Biomimetic polymers

Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 646

0014-3

doi:10

* C

Econo

E-

1.1. The conference series . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 646

1.2. Paradigm shift. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 647

057/$ - see front matter � 2004 Elsevier Ltd. All rights reserved.

.1016/j.eurpolymj.2004.10.035

orresponding author. Address: Department of Plastics and Rubber Technology, Budapest University of Technology and

mics, P.O. Box 91, H-1521 Budapest, Hungary. Tel.: +36 1 463 2015; fax: +36 1 463 3474.

mail address: [email protected]

mailto:[email protected]

646 B. Pukanszky / European Polymer Journal 41 (2005) 645–662

2. General aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 647

2.1. Interphase. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 648

2.2. Modification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 649

3. The role of interphases in various multicomponent materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 649

3.1. Fiber reinforced composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 649

3.1.1. General considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 649

3.1.2. Traditional fibers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651

3.1.3. Natural reinforcements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651

3.2. Particulate filled polymers and blends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651

3.2.1 Particulate filled polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651

3.3. Wood flour, hybrids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 652

3.3.1. Blends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 653

3.4. Nanocomposites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 654

3.4.1. Spheres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 654

3.4.2. Fibers and tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 655

3.4.3. Layered silicates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 656

3.5. Bio-related materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 657

4. Technological consequences and future prospects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 657

5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 659

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 659

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 659

1. Introduction

Multicomponent materials are used in increasing

quantities in all fields of the economy. They are present

in tools, utensils and devices used everyday at home, in

offices or in plants. Parts of our car or washing machine

are made of particulate filled or fiber reinforced compos-

ites, dental filling is a polymer nanocomposite, packag-

ing films are prepared from polymer blends or

multilayered structures, garden furniture usually con-

sists of CaCO3 filled polypropylene (PP), while racing

cars, parts of airplanes, rockets and helicopters contain

numerous parts of advanced composites. And the list

is endless. Most of these multicomponent materials

practically always consist of several phases, in which

interfaces exists between the phases. Interaction of the

phases across the interphase is one the factors determin-

ing the properties of these materials, thus the study and

modification of interfacial interactions are of utmost

importance for their further development. With the ad-

vance of science and technology and the introduction

of new materials the importance of interfacial interac-

tions does not diminish, on the contrary it considerably

intensifies, especially if we think of the rapid develop-

ment of nanocomposites, in which interfaces of enor-

mous size develop.

1.1. The conference series

Recognition of the facts mentioned in the previous

paragraph brought into life two conference series in the

80s. Since fiber reinforced composites cannot be pre-

pared without the perfect adhesion of the phases and ad-

vanced composites for military applications were very

much in the center of attention at that time, both series

focused on interfaces and interphases in composite mate-

rials. The idea of creating such a series was raised in Ja-

pan at a conference by the accidental meeting of Prof.

Hatsuo Ishida from Case Western Reserve University

and Prof. FransMaurer fromDSM. Their discussion ini-

tiated the series of ICCI (International Conference on

Composite Interfaces) organized by Prof. Ishida in

Cleveland. He was the chairman of the meeting for sev-

eral years and organized the conference at the same loca-

tion every other year. Later the meeting moved around

the world, the last meeting took place in China in 2002.

The second series, IPCM (Interfacial Phenomena in

Composite Materials), was initiated by Prof. Frank

Jones at the University of Sheffield, who organized the

first meeting with the journal Composites in 1989.

The overall scope of both conferences was the same

with slight differences in focus. Both invited papers on

interfaces and interphases in polymer (PMC), ceramic

Table 1

Scope and distribution (%) of papers presented at various

conferences on interfaces

Topic ICCI88 IPCM89 IIMM03

Polymer composites, fibers 61 68 47

Materials 11 9 2

Mechanics 12 23 13

Surface characterization 22 20 16

Surface modification 16 16 16

MMC, CMC 27 30 4

Blends, particulate filled

polymers

11 2 16

Nanocomposites 1 0 27

Others 0 0 6

B. Pukanszky / European Polymer Journal 41 (2005) 645–662 647

(CMC) and metal matrix composites (MMC). ICCI fo-

cused more on surface chemistry and modification, while

IPCM on micro- and macromechanical testing, model-

ing of interfaces and the determination of interfacial

adhesion. Table 1 compares papers published in the con-

ference proceedings of ICCI88 and IPCM89, respec-

tively [1,2]. Since the proceedings contained different

numbers of papers, the numbers in the table are given

as percentages. We must emphasize here that categoriza-

tion is very difficult and arbitrary. Most of the papers fit

into more than one category, thus the numbers in Table

1 are intended only to give a qualitative picture about

the main topics dealt with at the meetings. We can see

though, that papers on PMC represented about 70%,

while those on CMC and MMC approximately 30% of

the contributions at both meetings. Basically all papers,

98% of the total, were presented on ‘‘traditional’’ com-

posites at IPCM89, while close to 90% at ICCI88. The

slight difference in focus, i.e. mechanics vs. modification

and chemistry can be also seen in Table 1.

The focus of the two meetings remained more or less

the same for more than 15 years. The number of papers

presented on MMC and CMC decreased continuously

and so did the attendance. It became obvious relatively

soon that the area would hugely benefit from the merge

of the two meetings and the shift in scientific and com-

mercial interest required topical changes as well. Negoti-

ations to merge started in the middle of 90s and the final

decision was taken in 2001. The first joint meeting was

organized in 2003 in Hungary.

1.2. Paradigm shift

With the advance of detente, the interest of industry

as well as the academia partly shifted from advanced

composites to other heterogeneous systems, like nano-

composites, biomaterials, or natural fiber reinforced

composites. As a consequence, the scope of the new, uni-

fied conference was changed to reflect these develop-

ments and also the name of the meeting, Interfaces

and Interphases in Multicomponent Materials (IIMM)

was selected accordingly. The goals of the meeting were

to provide the scientific community with the opportunity

to present their latest results for discussion at a world-

wide forum, to create a friendly atmosphere for socializ-

ing and strengthening personal ties, to offer young

scientists an opportunity to present their work and inter-

act with the community, to enable scientists from East

and West to meet and discuss issues of common interest

and coordinate to some extent worldwide scientific activ-

ities. Although the traditional fields of glass, carbon and

aramid fiber reinforced composites were maintained in

the scope together with MMC and CMC composites,

numerous other fields, like nanocomposites and other

nanostructured materials, biomimetic materials and tis-

sue engineering were also included into the program.

The topics of oral papers presented at IIMM03 reflect

both the shift in the interest of the scientific community as

well as the success of the organizers in creating a meeting,

which reflects properly these changes. Table 1 compares

the scope of the papers to those presented at ICCI88

and IPCM89. Only about 50% of the presentations dealt

with ‘‘traditional’’ composites, and the rest with new

areas, the most important of which was nanocomposites.

Blends and composites maintained or increased their

role. Unfortunately the number of presentations on

bio-related materials remained low; the organizers have

not reached scientists active in this area.

Selected papers based on communications presented

at the Hungary meeting in 2003 are published in Com-

posite Interfaces and European Polymer Journal. The

editor of the latter asked the chairman of IIMM03 to

write this paper and present his views on the past, present

and future of research in interfaces and interphases in

multicomponent materials. We must emphasize here that

this is not a review paper offering a comprehensive survey

of a specific area. It rather gives the personal, often sub-

jective ideas of the author about the topic. Since he is less

familiar with some areas included in the scope of the

IIMM meeting, these views might be prejudiced or even

erroneous, and most probably not in line with the ideas

of experts. Nevertheless, we hope that the thoughts and

views expressed here may raise some thoughts and in-

crease the interest in this very important field, which will

gain even further significance in the future.

2. General aspects

The importance of interfaces and interphases is rec-

ognized by all those who are involved in the study of

heterogeneous multiphase materials. In some cases inter-

facial interactions are claimed to determine the proper-

ties of composites [3,4]. On the other hand, the

important role of interactions is often neglected com-

pletely and good adhesion of the phases is assumed a

priori, especially in advanced composites. Books on

Fig. 1. Dependence of interphase thickness on the strength of

interfacial interaction in polymer/CaCO3 composites [11].


advanced composites occasionally dedicate only a very

short section of a few pages to interaction, surface mod-

ification and characterization [5,6]. The difficulty of esti-

mating the role of interfaces and interphases may arise

from the fact that the type, mechanism and strength of

interaction developing between the phases in multicom-

ponent materials may vary in a very wide range as a

function of component characteristics. Even larger is

the number of methods used for the modification of

interactions, and surface treatment or coupling must

be adjusted to each individual system specifically. As a

consequence, different areas treat interactions separately

and rarely compare methods, phenomena or processes,

or try to draw conclusions of general validity from

observations. Conferences on topics dedicated to specific

areas, like fiber reinforced composites, blends, nanoma-

terials, or even bio-related substances usually accommo-

date a section on interfaces and interphases, but rarely

try to go out of their field and discover the findings of

others. However, interfacial interactions have some

common features, which are present in all heterogeneous

systems and they are worth to consider.

2.1. Interphase

The properties of all heterogeneous materials are

determined by the same four factors, by the characteris-

tics of the components, composition, structure and inter-

facial interactions. As a first approximation one could

assume that the interface is a well defined area with only

two dimensions. However, in heterogeneous systems an

interphase forms practically always, which has a thick-

ness, and properties differing from those of the compo-

nents. Such an interphase forms by the adsorption of

the polymer on the surface of the inclusion in particulate

filled polymers, by interdiffusion of the components in

blends or by various chemical reactions on fibers. These

latter are influenced also by the composition of the siz-

ing material and by changes in curing reactions. Because

of the multitude of interaction mechanisms and the com-

plicated structure developing as an effect, generalization

is difficult. However, the existence of the interphase is an

accepted fact now. As a consequence, more effort must

be done to determine its thickness and properties.

The interphase can be characterized by a large num-

ber of methods and numerous attempts were and are

done to do so. Spectroscopic methods are used for the

characterization of the chemical composition of surfaces

and interphases, as well as to follow the effect of surface

modification. Such methods like X-ray photoelectron

spectroscopy (XPS), secondary ion mass spectroscopy

(SIMS), Auger electron spectroscopy (AES), diffuse

reflectance infrared spectroscopy (DRIFT) and other

methods have different resolution and penetration

depth. However, it is very difficult to obtain information

about interphases which form by adsorption or interdif-

fusion. If the interaction forces are weak—sometimes

only dispersion forces act between the components like

in the blends of olefin polymers [7,8]—spectroscopic

methods do not help in their detection and even less in

the determination of their strength.

The effect of the interphase on the properties of a

multicomponent material depends on its amount and

characteristics. These latter depend very much on the

mechanism of interphase formation and on the proper-

ties of the components. If the interphase forms in chem-

ical reactions, the prediction of its properties is very

difficult. This happens during the silane treatment of fi-

bers or fillers, where usually a polysiloxane layers forms

around the inclusion. The thickness of this layer is deter-

mined mainly by the amount of silane used for treat-

ment, while its properties by the organofunctional

group of the compound [9,10]. If the interphase forms

by physico-chemical interactions, its thickness is deter-

mined by the strength of the interaction, while its prop-

erties by the characteristics of the components. The

effect of the strength of interaction is amply demon-

strated by Fig. 1, where the correlation of interphase

thickness and acid base interaction is presented for var-

ious particulate filled thermoplastic matrices containing

the same CaCO3 filler [11]. Besides the strength of inter-

action, the amount of material bonded in the interphase,

which depends also on the size of the interface and on

the contact area between the components, also influ-

ences the properties of the material. This factor becomes

extremely important in nanocomposites and is claimed

to endow these materials with exceptional properties.

In the previous paragraph we discussed interphase as

a phase with well defined properties, dimensions and

Table 2

Interphase thicknesses determined by different methods in particulate filled composites

Matrix polymer Dispersed component Determination method Thickness (lm) Ref.

HDPE SiO2 Extraction 0.0036 [19]

HDPE ’’ ’’ 0.0036 [20]

PP ’’ ’’ 0.0041 [20]

PP Graphite Model calculation 0.001 [21]

PS Mica Dyn. mech. spectra 0.06 [22]

PMMA Glass ’’ 1.4 [22]

PU Polymer ’’ 0.36–1.45 [23,24]

PP CaCO3 Modulus 0.012 [25]

PP ’’ Yield stress 0.15 [25]

PP ’’ Tensile strength 0.16 [25]


effect. We do not have sufficient space to discuss all de-

tails of these factors, but we must emphasize the con-

tradictions prevailing in this field and the need for

further study. Opinions are divided about the properties

of the interphase even in such simple materials as silica

filled PE. According to some sources a soft interphase

forms in such composites, while others claim the forma-

tion of a hard interlayer [12,13]. Models exist, which

take into consideration the formation of an interphase,

but assume a definite thickness and homogeneous prop-

erties inside the layer [14,15]. Opinions and models exist,

which assume that the properties of the interphase

change continuously from one phase to the other

[16,17]. In such cases either these graded properties or

average values must be taken into account during the

prediction of composite properties. Finally, the effect

of the interphase is different for each individual prop-

erty. Modulus is influenced very slightly by interaction,

while properties measured at larger deformation may

change considerably [18]. Similarly, the thickness of

the interphase determined indirectly from a composite

property depends very much on the method of determi-

nation. This point is demonstrated by Table 2 presenting

interphase thicknesses in various heterogeneous systems,

mainly particulate filled composites. According to the

table, the thickness of the interlayer increases with the

extent of deformation applied in the determination of

the property from which the layer thickness was derived.

2.2. Modification

Surface modification also has some general aspects.

One of them is the fact that a specific strategy must be

developed for each individual set of materials, general

solutions do not exist. The goal of modification must

be decided on first of all. If we want to decrease the

aggregation of fillers, non-reactive treatment must be

used, which decreases interactions. The phases are cou-

pled chemically in fiber reinforced composites, because

proper stress transfer can be achieved only in this way.

In this case surface chemistry must be adjusted to the

system, i.e. to the chemical character of the components.

It is rather surprising that such a strategy frequently is

missing and a treatment is expected to work in one sys-

tem, because it was efficient in another. Silanes are the

best examples; they are used for all kind of material

combinations irrespectively of the chemical composition

of the components. However, with the proper approach,

experience obtained in a system can be transferred to

others. The amount of surfactant or coupling agent must

be optimized in all composites. Organophilization of

layered silicates is carried out basically according to

the same principles as the coating of CaCO3. Specific

interactions are used in both cases, the ionic interaction

of chalk surface with the acid group in one case, or that

of the ammonium group with the negatively charged

surface of the silicate, in the other.

Besides these general aspects each group of materials

have specific features as well. In subsequent paragraphs,

we discuss the main groups of heterogeneous polymer

systems with regard to interfacial interactions and inter-

phases developing in them. We try to demonstrate issues

important for further development and questions to be

solved in the future.

3. The role of interphases in various multicomponent

materials

Multicomponent materials are arbitrarily divided

into four groups: fiber reinforced composites including

glass, carbon, aramid and natural fibers; particulate

filled composites and blends; nanocomposites and bio-

related materials. As mentioned previously, we do not

give a detailed survey of the various areas and do not

even try to be comprehensive, just demonstrate our ideas

with a few selected references.

3.1. Fiber reinforced composites

3.1.1. General considerations

The basic condition of the application of fiber rein-

forced composites is perfect adhesion between the com-

ponents. Already this statement is a much discussed

Fig. 2. Effect of various coupling agents on interfacial interac-

tion in PC/CF microcomposites. Symbols: (h) isocyanurate,

(}) isocyanate, (s) epoxy silane, (n) anhydride silane forming

a rigid, non-reactive polysiloxane layer.


question, but perfect adhesion is absolutely necessary to

transfer load from the matrix to the fiber. Without adhe-

sion the principle of fiber reinforced systems would not

work, i.e. the strong fiber carries the load, while the ma-

trix distributes it and transfers from one fiber to the

other. The opinion is often expressed that an excessively

strong interface leads to a rigid composite, while in the

case of weak adhesion the above mentioned principle

does not work, thus the strength of adhesion must be

set to an optimum value. However, a clear distinction

must be made here between interface and interphase.

In composites an interphase forms spontaneously even

in the absence of surface treatment. However, treatment

is always used in continuous fiber reinforced composites,

which invariably leads to the formation of an interphase

with a very complex structure [9,26]. As explained

above, the thickness and properties of this interphase

have crucial impact on composite properties. As a con-

sequence, adhesion must be perfect but the properties

of the interphase optimized in order to achieve advanta-

geous or desired properties. The correlations among the

chemistry, processing conditions, composition, structure

and properties of the interphase have not been fully

understood yet, they need further extensive study.

The fibers are usually treated, i.e. sized during their

preparation. In order to achieve high productivity, they

must be processed at a high rate. This requires special

sizings, which prevent fiber breakage and facilitate pro-

cessing. As a consequence, surface coating of all fibers

usually contain a number of additives, of which the cou-

pling agent comprises only a small part. Only limited

number of studies have been carried out on the analysis

of the composition of the sizing and its effect on compos-

ite properties [27,28]. Nevertheless, surface coating of

the fiber determines the structure and properties of the

interphase, as well as the quality of coupling.

The very strong adhesion necessary from efficient

stress transfer is usually achieved by the chemical cou-

pling of the fiber and the polymer matrix. Organofunc-

tional silanes are used the most often for all kind of

fibers. The chemistry and physics of coupling in glass

fiber reinforced thermosets is sufficiently known [9,29],

but there is much to be done in the case of carbon, ara-

mide and PE fiber reinforced composites. Efficient cou-

pling is usually not very simple, the lack of reactive

groups on the polymer prevent the direct coupling of

the components, or limit the number of covalent bonds

formed [30]. Often the modification of the matrix is re-

quired or a modified polymer is introduced into the

composite in order to achiever a high level of adhesion

[31]. Stress transfer is often achieved through a combina-

tion of several mechanisms, e.g. by chemical coupling

and interdiffusion like in glass fiber reinforced PP com-

posites. We must emphasize here again that chemical

coupling is system specific, the coupling agent and the

treatment technique must be selected according to

the characteristics of both components, i.e. fiber and

matrix.

An often neglected question is the amount of cou-

pling agent used. The treatment is usually done by the

producer of the fiber according to a proprietary tech-

nique which is not disclosed to the customer. The treat-

ment (sizing, coupling agent, composition) might be

optimized for a certain fiber/matrix combination, but it

does not necessarily work in other systems. It has been

shown many times that the structure and properties of

the interphase change with the amount of coupling agent

used [9], thus optimization is necessary in order to

achieve maximum efficiency.

The structure of the interphase is usually very com-

plicated. The most often used silanes chemically couple

to the surface of the fiber and through their free func-

tional group form a polysiloxane layer. Depending on

the composition of the matrix and the interphase they

may interdiffuse into each other forming a physically

bonded network [9,26]. The structure and composition

of the interphase can cover a very wide range, they de-

pend on the chemical composition of the components

(fiber, matrix, coupling agent), but they are strongly

influenced also by the composition of the sizing.

Depending on the organofunctional group of the silane

even a very hard interlayer may form on the surface of

the fiber preventing coupling as shown in Fig. 2 in which

interfacial shear stress (IFSS) of polycarbonate micro-

composites is plotted against the amount of coupling

agent used for the treatment of the fiber. The degree

of curing in the matrix close to the fiber is often smaller

than in the bulk material, which leads to a weak inter-

layer [32]. The application of an elastomeric interlayer


was also suggested to decrease stress concentration

around the fibers [3]. Although this might be advanta-

geous because it decreases stress concentration, the tech-

nique is rarely (or never) used in industrial practice. The

correlation between the structure and properties of the

interphase and the properties of the composites are not

known yet, much more research must be done in this

field. Experience indicates that a thin rigid interphase

leads to low fracture resistance, while a thick soft inter-

phase results in better fracture resistance, but lower com-

posite stiffness. However, quantitative correlations to

transfer these observations into practice are still lacking.

3.1.2. Traditional fibers

The general observations presented above are valid

for all fiber reinforced composites. The interest in these

materials, especially in carbon fiber reinforced compos-

ites decreased somewhat in recent years. The price of

carbon fibers did not decrease to the extent expected,

the aviation industry went through a crisis and some

accidents could undoubtedly be related to the failure

of composite parts. Nevertheless, research continues.

Review papers were published on carbon fibers [33]

and also on surface modification used to improve the

properties of their composites [34]. New methods of sur-

face modification are tried or even introduced into prac-

tice. One of the techniques which is already discussed for

years as a possible means to modify the surface proper-

ties of fillers [35], glass [36,37] and carbon fibers [38] is

plasma treatment, but its introduction into industrial

practice is still outstanding. Ultrasonic treatment is also

used to improve the homogeneity of the treatment and

interphase properties [39]. Although continuous study

and development may lead to further improvement of

existing technologies, revolutionary changes are not ex-

pected to occur in this area in the near future.

3.1.3. Natural reinforcements

Instead of traditional fibers, recently attention is fo-

cused much more on natural reinforcements. A very

large number of papers are published on the advantages

and potential applications of wood flour, as well as all

kinds of natural fibers and several reviews are also avail-

able [40–43]. These materials are claimed to have numer-

ous advantages, they come from renewable resources,

are environmentally friendly, light and strong, etc. On

the other hand, these fibers also have some disadvan-

tages, the properties change from season to season, the

fibers are sensitive to water and their transverse strength

is rather poor. Interfacial adhesion must be very good

also in natural fiber reinforced polymers thus many of

the papers mentioned above focus attention on surface

modification and coupling. Besides surface treatment,

chemical modification of the fiber by impregnation is

also carried out to improve fiber properties especially

to decrease water adsorption. In spite of the enormous

interest in natural fibers and in their modification, male-

inated polymers are used for coupling in most cases, at

least in polyolefin composites [42]. More research is

needed to develop practically viable methods for the

modification of these fibers in order to decrease water

sensitivity and improve reliability. In spite of the difficul-

ties, a large increase is expected in the use of such mate-

rials in the future.

3.2. Particulate filled polymers and blends

3.2.1. Particulate filled polymers

Particulate filled polymers and blends represent two

mature areas in the field of heterogeneous polymers.

The use of fillers dates back for a long time. Fillers and

reinforcements were and are used in thermoset matrices,

but also in all kinds of thermoplastic polymers. Particu-

late filled polymers are used in large quantities in many

fields of application from household appliances to auto-

motive parts. This well established position in the plastics

industry creates the impression that all problems of the

production and application of particulate filled polymers

have been already solved, but in reality many questions

need further investigation. Although research on blends

and composites is not in the main streamline of interest

any more, a steady number of publications indicates

the importance of the field. This interest is demonstrated

well by the recent publication of two large monographs

on particulate filled polymers [44,45]. One, Ref. [44] is

rather poor in quality, a mere compilation of informa-

tion collected by online computer search. Its main merit

is the list of references, which can be used for the detailed

study of a specific question of interest. The other is the

second edition of a successful book edited by one of

the experts of the field, Rothon [45], professionally

sound, a book which offers valuable information in all

questions related to particulate filled polymers. The con-

tinuous interest in the area is sufficiently proved also by

Table 1; the number of papers on blends and particulate

filled polymers remained at a relatively high level.

Most of the unresolved questions in blends and com-

posites are related to interactions. In particulate filled

polymers two types of interactions may be distinguished.

Particle–particle interactions lead to aggregation, while

matrix–filler interactions determine micromechanical

deformation processes as well as the macroscopic behav-

ior and performance of the material. Relatively few

papers are published recently, which are related to

aggregation [46,47]. The detection and quantitative

characterization of aggregation is difficult, unambiguous

methods do not exist yet. Although general tendencies,

i.e. the increase in the extent of aggregation with

decreasing particle size and increasing filler content,

are known, exact correlations do not exist in spite of

the fact that aggregation is one of the major issues in

the production of particulate filled polymers.

Fig. 3. Structure of a breathable film prepared from PE/CaCO3

composite. The SEM micrograph taken from the fracture

surface of a broken film shows the voids around the particles

throughout the entire cross-section.


A large number of the papers published in this field,

maybe even their majority, are related to the modifica-

tion of interfacial interactions, specifically to the surface

treatment of the filler. A considerable number of these at-

tempts describe surface modifications through the use of

reactive compounds, mainly silanes and titanates [48–

50]. Often considerable improvement in properties is re-

ported, even when the data presented in the paper do

not support the statement. In the majority of the cases

the philosophy of the treatment is unclear and the

amount used is arbitrary, is not adjusted to the surface

characteristics as well as area of the filler and to the

chemistry of the coupling agent. Although silanes were

shown to increase interaction also in PP/filler composites

[51,52], one cannot expect chemical interaction from a fil-

ler not containing active—OH groups on its surface (talc,

CaCO3) or from polymers not having reactive groups at

all (PP, PE). Apart from the fact that coupling agents

often are not adjusted properly to the system, they are

also expensive and not worth to use in an application,

the goal of which in not to increase, but decrease interac-

tion. The usual purpose of the surface treatment of par-

ticulate fillers is to decrease their surface free energy in

order to hinder particle/particle interactions and aggre-

gation. The best way to achieve this goal is the use of long

chain fatty acids. On the other hand, the development of

proper surface treatment technology and the optimiza-

tion of the type and amount of surfactant require knowl-

edge and skill, as well as further studies.

An increasingly important question, which is not ad-

dressed sufficiently, is the study of the micromechanical

deformation processes occurring in particulate filled

polymers, in fact in all heterogeneous polymer systems.

Under the effect of external load stress concentration

develops around the inclusions, which induces local

deformations. In particulate filled polymers the domi-

nating micromechanical deformation process is thought

to be debonding, but considerable shear yielding also

takes place. Other deformations like matrix cracking

or crazing may also occur in these systems. Although a

model developed earlier predicts well the conditions of

debonding [53], it does not give information about the

relative significance of various deformation processes.

Debonding is a process which is used in industrial prac-

tice to produce breathable films [54]. Polyethylene films

are prepared with large amounts of CaCO3 filler, the

films are stretched producing voids, which permit the

passage of vapor, but are not permeable to liquids (see

Fig. 3). The extent of debonding determines moisture

vapor transport (MVTR) through the film, thus the

quality of the product. Interfacial adhesion is one of

the factors determining debonding and its control makes

possible the improvement of product quality in an

important and rapidly developing field. Breathable films

serve as a good example for the importance and poten-

tials of particulate filled composites, which allow the

production of high-tech products from simple materials

with a delicate technology.

3.3. Wood flour, hybrids

Two other areas must be mentioned which are in the

center of interest or deserve more attention. A large

number of papers are published on fillers or reinforce-

ments obtained from renewable resources. Wood flour

filled polymers are typical particulate filled polymers,

in which interactions are of utmost importance, espe-

cially if we consider the large size of the wood particles.

These materials were mentioned already in the previous

section. On the other hand, hybrid composites contain-

ing two different fillers or a filler and an elastomer need

more attention [55,56]. These materials also have practi-

cal importance, e.g. PP containing a filler and an elasto-

mer is extensively used for the production of automotive

bumpers. Such hybrids are continuously studied since

the 70s, but general correlation between their structure

and properties are still not known. It has been shown

that two boundary structures may develop in such mate-

rials. The filler and the elastomer may be dispersed sep-

arately in the polymer matrix or the elastomer may

encapsulate the filler and the inclusion formed in this

way is dispersed in the continuous phase. Detailed study

of a PP/EPDM elastomer/CaCO3 filler composite system

proved that that the prevailing structure is determined

by the relative magnitude of adhesion and shear forces

[57]. In practice always mixed structures form. In

Fig. 4 the Young�s modulus of three-component PP

composites of various compositions is plotted against

the relative amount of filler embedded by the elastomer.

According to the figure the stiffness of the material is

determined by the extent of embedding. On the other

hand, fracture resistance is influenced also by other fac-

tors (Fig. 5) [58]. In practice high stiffness and toughness

Fig. 4. Dependence of the stiffness of three-component PP/

EPDM/CaCO3 composites on embedding expressed as a

percentage of total filler content. Young�s modulus decreases

significantly as the number of embedded particles increases;

embedding dominates stiffness.

Fig. 5. Correlation between the extent of embedding and

impact resistance in three-component PP/EPDM/CaCO3 com-

posites. Deviation from the linear correlation indicates the effect

of other factors than encapsulation.


are required simultaneously from these materials, which

is very difficult to achieve. Only further study can lead to

a knowledge, which makes possible the design of com-

posites with optimum or required properties.

3.3.1. Blends

Similarly to particulate filled composites, interactions

are the dominating factors also in polymer blends. Inter-

action or the lack of it determines miscibility, phase

structure and properties of the blends. In spite of the fact

that blends are routinely and extensively used in indus-

trial practice, a large number of papers are still being

published in this area, as well. These focus on miscibil-

ity, structure, compatibilization and properties. Misci-

bility of the components is predicted with various

models and theories [59] and the development of more

and more sophisticated methods make possible the

proper characterization of phase structure [60–64]. Sim-

ulation methods are used for the prediction of miscibility

and structure of polymer pairs with increasing frequency

[65,66]. Other papers focus on structure and properties,

while a major issue both in academia [67] and in industry

[68] is the compatibilization of blends.

Unfortunately, the field, and also the papers pub-

lished, can be divided into two well defined groups with

very little connection between the two groups. This divi-

sion is well demonstrated by the two volume book pub-

lished recently on blends in the edition of Paul and

Bucknall [69]. The first volume gives a comprehensive

account of the latest developments in all aspects of poly-

mer miscibility from statistical thermodynamics through

hydrogen bonding systems to polyolefin blends, dis-

cusses characterization techniques and the factors affect-

ing structure formation. The second volume deals with

the performance of the blends, mechanical properties

and fracture characterization, fatigue, toughening mech-

anisms, specific properties like light transmission and

permeability, as well as reinforced and elastomeric

blends. However, in this second volume any thermody-

namic parameter related to miscibility appears only once

or twice, i.e. general correlation between miscibility,

structure and properties is not mentioned, or not

known. However, most of the blends are used in struc-

tural applications and the prediction of mechanical

properties would help very much the development of

new and better materials. An attempt was made earlier

to develop a simple model, which relates miscibility

and mechanical properties [70]. Its application led to a

relatively good correlation between a parameter derived

from mechanical properties, from the effective load bear-

ing capacity or the dispersed phase, and the Flory–Hug-

gins parameter determined by solvent diffusion (Fig. 6)

[71–73]. In spite of the surprisingly good general ten-

dency and validity for the most different polymer pairs,

the model is very simple, applies numerous simplifying

conditions and neglects important factors, thus it needs

considerable improvement and refinement.

Bio-related materials gain increasing importance also

in the research and technology of polymer blends. Poly-

mers from renewable resources, e.g. starch and cellulose,

are used as components of blends or composites and at-

tempts are made to produce biologically degradable

polymers by the combination of such materials and poly-

esters produced by synthetic or natural processes. Results

are still reported on thermoplastic starch/polyolefin

blends in spite of the fact that suchmaterials were already

Fig. 6. Correlation between the Flory–Huggins parameter for

polymer–polymer interaction determined form solvent diffusion

and parameter C derived from the tensile strength of the blends,

which is related to the load bearing capacity of the dispersed

phase.


produced in industrial scale already 15 years ago [74–76].

Moreover, the ban of such materials is considered in

some countries because they fear that the fine polyolefin

powder forming during the degradation of such materials

blocks the soil and hinders the penetration of water, or

covers lakes ruining living environment. Blends contain-

ing starch or cellulose and aliphatic polyesters either

from synthetic or microbial sources seem to have more

potential in the future [77,78]. However, considerable re-

search must be done to improve their properties and de-

crease price. All cellulose composites may also develop to

materials of some practical importance in the future,

although the technology needs further development [79].

3.4. Nanocomposites

One of the buzz words in the technical world includ-

ing polymer science is nano with all the positive and

negative consequences. In recent years practically every-

thing became ‘‘nano’’ even materials which are around

for more than a hundred years like carbon black used

for the reinforcement of rubbers. Many laboratories

launched projects on composites containing particles in

the nanometer scale with variable extent of success.

The general idea of nanocomposites is based on the con-

cept of creating a very large interface between the nano

sized building blocks and the polymer matrix. However,

the properties of nanocomposites are not determined

only by the size of the interface, interaction is a crucial

factor again. Very often already the homogeneous distri-

bution of the nanosized particles is problematic, i.e. the

expected large surface cannot be always created, but the

adjustment of the proper interaction or coupling of the

components presents further problems. The coupling

agent or surface modification is often not properly se-

lected, it is not adjusted to the system, and thus the

material does not possess the expected property combi-

nation. Nanocomposites can be classified in many ways;

we discuss them here according to the dimensionality of

the nanosized heterogeneity.

3.4.1. Spheres

Spherical or nearly spherical particles have all three

dimensions in the nanometer range. Numerous attempts

have been made to distribute such particles in a polymer

matrix with the most different methods. One approach is

the use of traditional thermoplastic or thermoset technol-

ogies to homogenize the previously prepared particles

into the matrix polymer. Carbon black, precipitated cal-

cium carbonate and silica are the most frequently used

representatives of this class of materials. They were

around before the nano era and are used in specific appli-

cations. Interaction and its control is the key for success

also in the application of these materials, but particle–

particle interactions are usually more important than

polymer–filler adhesion. It has been shown earlier that

the occurrence and extent of aggregation depends on

the relative magnitude of adhesion and shear forces

[80]. The ratio of the two forces depends on interfacial

adhesion, shear forces and the size of the particles; the

aggregation tendency of fillers increases strongly with

decreasing particle size. Since in nanocomposites parti-

cles are very small, aggregation is practically unavoidable

and the formed structure governs the properties. The size

and interaction of the particles determine also the

strength of the aggregates. Although attempts have been

made to describe aggregation strength, further research

must be done in this area. The consequence of insufficient

aggregate strength is demonstrated by Fig. 7 showing the

failure of a large CaCO3 aggregate formed in a PP ma-

trix. Under the effect of external force the aggregate frac-

tures leading to the premature failure of the entire

composite. Shear forces can be changed in a limited range

thus the main factor to control aggregation is the surface

modification of the filler. Various treatments and modifi-

cation techniques are used, e.g. surface grafting of the sil-

ica [81,82], but aggregation can be rarely avoided.We can

hope only for a decrease in its extent at most. This ap-

proach, i.e. the distribution of preformed particles in a

matrix with traditional techniques, must improve consid-

erably in order to produce nanocomposites with the

expected and forecasted exceptional properties.

The simultaneous formation of the particles and the

polymer matrix, usually in sol–gel technology, seems

to have much more potentials. The interest in organic–

inorganic hybrids dates back to the 80s and several re-

views are available in this field summarizing the tech-

nical possibilities, structure, properties and potential

Fig. 8. An acrylate functionalized POSS cage.

Fig. 7. Inferior strength and fracture of a CaCO3 aggregate

consisting of 0.08 lm large primary particles under the effect of

external load.


applications of these materials [83–85]. Usually silicate

chemistry is used to produce particles of different sizes

[86] or organic–inorganic networks [87]. The size of the

particles can be changed from 500 to 10 nm by modify-

ing the conditions of the polymerization, hydrolysis and

condensation of the silica precursors [86]. The homoge-

neity of the composite is much better in these materials,

although depending on chemistry aggregates can form

even in this case [86]. Interfacial interactions can be also

adjusted by using the proper reactants to introduce func-

tional groups to the surface of the filler. These groups

can react with the polymer during polymerization or

cross-linking. This technology may lead to nanocompos-

ites with controlled structure and interfacial adhesion,

thus materials with tailor made properties can be pro-

duced for the most diverse applications.

Another class of materials which created much inter-

est recently and appear to have great potentials in vari-

ous fields of application is polyhedral oligomeric

silsesquioxane (POSS). Possible applications are cataly-

sis, precursors to silicates, preparation of copolymers

and hybrid networks. Interest and the intensity of re-

search increased further by the commercial availability

of the material. POSS cages (Fig. 8) can be functionalized

by various methods like grafting groups on preformed

clusters or particles, or by the formation of functional

groups during particle formation [85]. One way of mod-

ification is the hydrosilylation of SiH groups present on

the surface of the POSS cube with any unsaturated bond

in the presence of a catalyst. Various functional groups

like epoxy, styril, norbornyl, methacrylate, etc. can be

formed on the surface of the POSS compound [88,89].

The reactive groups available encompass a wide range

offering a large number of possibilities for further modi-

fication and the control of the structure and/or chemistry

of the compounds. Nanocomposites with a wide variety

of structures can be formed in this way. POSS can be

build into the chains, can be attached to them by a

spacer, can form networks, etc. Moreover, besides POSS

other hybrid organic–inorganic supermolecular assem-

blies can be also prepared e.g. from butyltin oxo–hydro-

xo nanobuilding blocks and dicarboxylates, as well as by

related chemistry [90]. By changing structure and func-

tionality, the properties of the composites can also be

modified according to requirements. Although the chem-

istry is not simple, the potentials of the approach are

large and homogeneity, as well as interactions, can be

kept under control relatively easily, at least compared

to traditional homogenization technology.

3.4.2. Fibers and tubes

Similarly to POSS, carbon nanotubes are also in the

focus of attention for some time. Nanotubes and nano-

fibers have two dimensions in the nanometer range; they

are usually micrometer or even millimeter long. They at-

tracted the interest mainly because of their exceptional

mechanical [91] and electrical properties [92]. Theoretical

and experimental investigations proved that carbon

nanotubes have a Youngs�s modulus in the range of

1.2 TPa, but they are also flexible [93]. The extremely

high stiffness would make these materials ideal reinforce-

ments for composites. The ultimate goal of composite

preparation, i.e. producing materials with high stiffness

and toughness at low reinforcement content, could be

achieved with the nanotubes. However, effective rein-

forcement has two conditions: alignment parallel with

the direction of the load, and good stress transfer from

the matrix to the fibers. Unfortunately, both are difficult

to achieve in this case. Carbon nanotubes form bundles

and they are usually twisted. Separation of the individual

tubes, their homogeneous distribution and parallel align-

ment are problems to be solved in the future. Moreover,


similar difficulties arise with stress transfer controlled by

interfacial adhesion. Although experiments directed to-

wards the determination of interfacial fracture energy

in multiwalled carbon nanotubes reinforced composites

indicated the existence of a ‘‘relatively’’ strong interface

[94], interfacial adhesion is insufficient in most cases in

spite of the small diameter of the fibers.

Carbon nanotubes have a very regular structure al-

most exclusively consisting of carbon atoms. The surface

free energy of the tubes is low and they do not contain

reactive groups necessary for coupling. The importance

of interfacial interactions in the preparation of carbon

nanotube reinforced composites was recognized by some

groups, Gong et al. [95] declared it as one of the most

critical issues. They used a surfactant processing aid to

improve the properties of a carbon nanotube/polymer

composite, they could increase the Tg of the polymer

and its stiffness in this way. Although a surfactant may

improve homogenization, it is difficult to see how it

can improve interfacial adhesion. Other attempts were

also made to improve interfacial adhesion by the func-

tionalization of the tubes; an improvement of properties

was reported invariably as an effect of modification

[96,97]. In spite of the huge effort and intensive study,

carbon nanotube reinforced composites do not meet

expectations yet, their performance is moderate at most,

especially if we compare it to their price. A possible way

to overcome the difficulties caused by the shape and con-

formation of nanotubes is the use of nanofibers pro-

duced by electrospinning. According to Dzenis [98]

these fibers are superior to nanotubes in many respects,

although the way to control interfacial interactions is

unclear also in this case. Although these fibers have

much potential in nanofabrication processes [99] and

they may have numerous advantages including price,

much has to be done before they can be used as rein-

forcements at industrial scale.

3.4.3. Layered silicates

Nanoreinforcements with only one dimension in the

nanometer range can be achieved by platelets, usually

single silicate layers. Layered silicate polymer nanocom-

posites also created much interest especially since the

results of the Toyota laboratory have become public

[100,101]. Intensive research has been carried out in this

area by many laboratories since then on all kinds of poly-

mers incorporating layered silicate particles. Several re-

view papers and books were also published about the

preparation, structure, properties and possible applica-

tions of these materials [102–106]. Montmorillonite or

hectorite is used the most often as reinforcement. Inter-

actions play a crucial role also in layered silicate nano-

composite preparation. The negative surface charge of

the silicate layers is compensated by solvated cations in

the space confined between two layers, called also the gal-

lery, which can be and are exchanged to organic ions,

mostly by ammonium ions having one or more long ali-

phatic tails. Ion exchange leads to an increase of gallery

distance and to a decrease of attractive forces between

the layers. The decrease of intergallery forces makes

exfoliation possible, which is basically the separation of

the silicate layers. Delamination, or exfoliation, can be

initiated by in situ polymerization or by shear in a con-

ventional processing machine. Practically all the papers

published in this field emphasize the advantages of nano-

composites and often claim complete or at least extensive

exfoliation. Unfortunately, it is rather difficult to achieve

complete exfoliation and usually a complex structure

forms containing large particles, tactoids with extended

gallery distances and individual exfoliated silicate layers.

The determination or estimation of the extent of exfolia-

tion is difficult; drawing conclusions from WAXS pat-

terns [107] may be very misleading. Properties often do

not improve to the extent as expected [108,109] or even

deteriorate [110,111]. Naturally very few papers report-

ing negative results are available although such informa-

tion would also help to increase our knowledge about

factors controlling nanocomposite properties.

The reason for the difficulties to reach complete exfo-

liation can be traced back to interactions. Beside organ-

ophilization, very often additional swelling agents, or

compatibilizers, must be used to increase the extent of

exfoliation and to improve homogeneity [106,107,112].

However, interactions are equally important also for

the determination of properties. A generally accepted

and frequently published view is that the hydrophilic sil-

icate layers are not compatible with the hydrophobic

polymers. Organophilization makes the silicates also

hydrophobic thus compatibility and interaction improve

[104]. In our view this approach, explanation or inter-

pretation is not true and completely misleading. It is

common knowledge that polyethylene and polystyrene

are not miscible or compatible. Why do we expect the

compatibility of a silicate layer to increase in any poly-

mer except PE, if we cover its surface with aliphatic

chains? Moreover, it has been shown a long time ago

that the non-reactive coating of a mineral filler with a

surfactant leads to a decrease in its surface tension and

also in matrix/filler interaction [113]. High energy sur-

faces, like that of the silicates in question are always wet-

ted by low surface energy liquids like a polymer melt

[114]. Obviously the necessity to increase the distance be-

tween the layers of the silicate and to decrease intergal-

lery bonding forces to achieve exfoliation is confused

with its effect on polymer/silicate interaction. As a final

example, we present two figures showing the transpar-

ency and tensile strength of PVC/silicate composites.

The optical transparency of the composite containing

the organophilic silicate is significantly larger than that

of the material prepared with the neat filler (NaMMT),

which indicates at least partial exfoliation (Fig. 9). On

the other hand, its strength is lower because surface

Fig. 10. Effect of interfacial interaction on the tensile yield

stress of PVC/MMT composites: (h) NaMMT and (n)

OMMT.

Fig. 9. Dependence of the transparency of PVC/MMT com-

posites on silicate content: (h) NaMMT and (n) OMMT.


modification decreases the matrix/silicate interaction

(Fig. 10). Weak interaction led to decreased strength in

spite of the large contact surface [111]. In conclusion,

much has to be done to properly understand the role

of interfacial interactions in these layered silicate nano-

composites in spite of the fact that some compounds find

already industrial application [115].

3.5. Bio-related materials

The incentive to use biologically active materials is

increasing by the day. As mentioned earlier, materials

from renewable resources are used as natural reinforce-

ments or components in polymer blends. The abundance

and low price of natural polymers, like starch and cellu-

lose, make them attractive for industrial applications.

Considerable effort is done to replace synthetic poly-

mers, or fibers, with these materials. We pointed out

the importance of interfaces and interphases also in

the development of bio-related blends and composites.

Surface modification and adjustment of interfacial inter-

actions is the necessary and proper way to control struc-

ture and properties of such materials.

A partly similar and partly different area is the devel-

opment of biomimetic polymers for various applications

in the human body. Basically the same, or very similar

materials, are used for such applications as for blends

and composites. Polyethylene hip joints are used for a

long time and experiments are done to use injection

molded biodegradable starch-based polymeric scaffold

in tissue engineering [116]. Interfacial interactions are

equally, or even more, important in these materials than

in other multicomponent systems. Materials in the

human body interact with cells and tissues and the

chemistry of the material must be selected accordingly

to initiate the proper response from the living cells. Fur-

thermore, the formation of new tissues must be mediated

by biomolecular recognition. Such a response from cells

is achieved by the surface or bulk modification of bio-

materials by chemical or physical methods with bio-

active molecules like proteins or peptides. A recent

review gives a detailed account about the surface and

bulk modification of biomaterials with cell recognition

molecules to design biomimetic materials for tissue engi-

neering [117]. The criteria of design including the con-

centration and spatial distribution of modified

bioactive materials are also evaluated in the paper.

Other review papers [118] and books [119] are also avail-

able discussing tissue engineering as well as synthetic

biodegradable polymer scaffolds and the Journal Bioma-

terials dedicated a complete issue to such materials [120].

All these papers send the message that surface modifica-

tion is the key issue to the success of the preparation of

biomimetic polymers, but modifying molecules must be

adjusted even more precisely in the living environment

than in engineering materials, because of the specific rec-

ognition capability of living organisms. Although all

surface modifications are system specific, in biomimetic

materials this reaches the highest level possible.

4. Technological consequences and future prospects

Development in the areas discussed in previous sec-

tions is driven only partially by the curiosity of the sci-

entific community. Possible application areas are

always kept in mind and a large part of the research is

focused on the development of new materials with a


lower price or better properties. In traditional areas like

fiber reinforced composites, particulate filled polymers

and blends development is directed towards price de-

crease, improved technology and advanced properties.

Recently a survey was published on the internet present-

ing growth opportunities in the carbon fiber market

[121]. The analysis predicts more then 10% growth per

year in certain application areas of carbon fibers and a

significant decrease in their price. Although such a de-

crease in price has been forecasted for some time, it

has never occurred; this may happen in the near future.

Similarly, a higher than average growth rate is fore-

casted in other areas of heterogeneous polymeric materi-

als, e.g. the market of compatibilizers is expected to

grow by 5.4% per year by 2005 [68]. The interest and in-

crease in the use of wood/plastic, natural fiber reinforced

and natural composites is demonstrated by several re-

ports and surveys [122–124], according to one of which

the growth rate of these materials is 12% per annum in

the US [122]. These reports clearly show that the pro-

duction of multicomponent multiphase materials is

increasing continuously and we can expect the tendency

to continue.

We hoped to show in previous sections that one of

the key factors in the development of new technologies

for the production of these materials and new combina-

tion of materials is the proper adjustment of interfacial

interactions. The importance of interactions is proven

by the numerous attempts to modify them. Some kind

of surface modification is used practically in all hetero-

geneous systems. The goal, method and solution are dif-

ferent in all cases and must be adjusted to the

components. Surface modification by non-reactive treat-

ment, coupling or any other technique is in the focus of

attention. In the case of particulate filled polymers devel-

opments in grinding and separation technology should

result in fillers with controlled particle size (contact sur-

face, deformation mechanism), while surface modifica-

tion controls the aggregation tendency of the filler.

Further progress is expected, for example, in the devel-

opment of breathable films and other high-tech prod-

ucts. Practically the same applies to polymer blends in

which compatibilizers or blending agents are used to im-

prove processability, the stability of the developed struc-

ture and properties. Better stability of the blend

structure leads to a simpler technology, single screw

extruders may be used instead of twin screw machines

[68]. Interfaces and coupling are crucial for fiber rein-

forced plastics as well. As shown above, the fastest

development is expected from natural fiber reinforced

polymers and blends containing natural polymers.

The technological relevance of controlling interac-

tions is even more important for nanocomposites. The

use of these materials is often hindered by the inade-

quacy of technology. Although layered silicates are used

in several application areas, mostly in the automotive

industry [115], the total amount used is low. General

Motors, a pioneer in the use of thermoplastic olefin

(TPO) nanocomposites, uses about 250 tons of compos-

ites per year in its various models [115]. Before a consid-

erable breakthrough is reached, better understanding of

interactions must be achieved in order to control exfoli-

ation, and generally structure. This also requires the

development of principles and methods for the proper

characterization of the multilevel structure of these

materials from the extent of exfoliation to the determi-

nation of the presence of non-exfoliated particles or clay

scaffolds. The adjustment and design of the strength of

interaction, as well as the structure and properties of

the interphase formed need further research in this area.

Interactions and their control are equally important in

carbon nanotube and nanofiber reinforced polymers.

However, the development of proper technology to align

the fibers might largely facilitate the introduction of

these composites into practice. Before this problem is

solved such composites may find application only in lim-

ited areas. The very specific role of interactions in biomi-

metic materials, as well as their particular use, requires a

completely different approach and philosophy. Never-

theless, traditional technologies may play also a role

here shown by the attempt to produce biodegradable

scaffolds for tissue engineering by injection molding

[116].

It is very difficult even to try to envisage future trends

and tendencies in this rapidly developing area. However,

a breakthrough may occur at any time in most fields as a

result of the intensive research pursued currently. Fur-

ther growth may be forecasted in traditional heteroge-

neous muticomponent materials like particulate filled

polymers, blends and fiber reinforced composites. The

application of nanocomposites might be restricted to

specific fields until a better understanding of structure–

property correlations are obtained and the improvement

of processing technology leads to lower price and better

control of properties. These materials cannot compete

with particulate filled and fiber reinforced composites

in bulk applications, like household appliances or build-

ing materials. On the other hand, their barrier properties

and improvement of flammability may find application

in several areas. Nanotechnology might be used also in

the preparation of special films and coatings. Carbon

nanotubes and nanofibers may find application in the

electric or electronic industry, or in places where anti-

static properties are needed. Carbon nanotubes improve

conductivity already at a very low concentration because

of the low percolation threshold of the thin fibers. We

expect continued interest in raw materials from renew-

able resources, and in fact in all bio-related materials.

Better understanding of interfacial interactions and the

development of proper surface modification will be a

central question as well as the driving force of develop-

ment in all of these areas.


5. Conclusions

Interfacial interactions and interphases play a key

role in all multicomponent materials irrespectively of

the number and type of their components or their actual

structure. Recognition of the role of the main factors

controlling interfacial adhesion and proper surface mod-

ification may lead to significant progress in many fields

of research and development, as well as in related tech-

nologies. It may be the key to reach the breakthrough in

nanocomposites the industry is waiting for, but it may

bring progress also in other areas. Although the role

and importance of interfaces and interphases are the

same for all multicomponent materials, surface modifi-

cation must be always selected according to the objec-

tives targeted, as well as to the characteristics of the

particular system. Efficient surface treatment or cou-

pling alone might not achieve the desired goal, we must

always keep in mind that an interphase forms always in

such materials and the control of interphase properties

must be part of the modification philosophy. The use

of multiphase, multicomponent materials is expected

to grow with a larger than average rate also in the fu-

ture. It is important to keep the interdisciplinary nature

of the area, since principles and techniques developed by

one field may find application also in other areas.

Acknowledgments

The author is indebted to all his colleagues, to Agnes

Abranyi, Lıvia Danyadi, Erika Fekete, Szilvia Klebert,

Janos Moczo, Peter Muller, Andras Pozsgay and Laszlo

Szazdi, who supplied information to this publication.

The help and support of the editor of EPJ, Julius Vancso

is also acknowledged. Research on the interfaces and

interphases of heterogeneous polymer systems going

on for many years in our laboratory is partly supported

by the National Scientific Research Fund (OTKA Grant

No. T043517).

References

[1] Ishida H. Interfaces in polymer, ceramic, and metal

matrix composites. New York: Elsevier; 1988.

[2] Jones FR. Proceedings of the international conference on

interfacial phenomena in composite materials. Lon-

don: Butterworths; 1989.

[3] Kardos JL. The role of the interface in polymer compos-

ites—some myths, mechanisms, and modifications. In:

Ishida H, Kumar G, editors. Molecular characterization

of composite interfaces. New York: Plenum; 1985. p.

1–11.

[4] Eirich FR. Some mechanical and molecular aspects of the

performance of composites. J Appl Polym Sci Appl

Polym Symp 1984;39:93–102.

[5] Pilato LA, Michno MJ. Advanced composite materi-

als. Berlin: Springer; 1994.

[6] Chawla KK. Composite materials, science and engineer-

ing. New York: Springer; 1987.

[7] Mader D, Brach M, Maier RD, Stricker F, Mulhaupt R.

Glass transition temperature depression of elastomers

blended with poly(propene)s of different stereoregulari-

ties. Macromolecules 1999;32:1252–9.

[8] Szabo P, Pukanszky B. Miscibility of crystalline and

amorphous polymers: polyethylene/polyisobutylene

blends. Macromol Symp 1998;129:29–42.

[9] Ishida H, Miller JD. Substrate effects on the chemisorbed

and physisorbed layers of methacryl silane modified

particulate minerals. Macromolecules 1984;17:1659–66.

[10] Demjen Z, Pukanszky B, Foldes E, Nagy J. Interaction of

silane coupling agents with CaCO3. J Colloid Interface Sci

1997;190:427–36.

[11] Moczo J, Fekete E, Pukanszky B. Acid–base interactions

and interphase formation in particulate filled polymers.

J Adhesion 2002;78:861–75.

[12] Maurer FHJ, Kosfeld R, Uhlenbroich T, Bosveliev LG.

Structure and properties of highly filled high-density

polyethylene. In: 27th Intl Symp on Macromolecules,

Strasbourg, France, 6–9 July 1981.

[13] Vollenberg PHT, Heikens D. Particle size dependence of

the Young�s modulus of filled polymers 1. Preliminary

experiments. Polymer 1989;30:1656–62.

[14] Tong Y, Jasiuk I. The effect of interface on the mechan-

ical properties of composites. In: Ishida H, editor.

Interfaces in polymer, ceramic, and metal matrix com-

posites. New York: Elsevier; 1988. p. 757–64.

[15] Maurer FHJ. Interface effect on viscoelastic properties of

polymer composites. In: Sedlacek B, editor. Polymer

composites. Berlin: Walter de Gruyter; 1986. p. 399–411.

[16] Broutman LJ, Agarwal BD. A theoretical study of the

effect of an interfacial interlayer on the properties of

composites. Polym Eng Sci 1974;14:581–8.

[17] Voros Gy, Pukanszky B. Modeling of the effect of a soft

interlayer on the stress distribution around fibers: longi-

tudinal and transverse loading. Macromol Mater Eng

2002;287:139–48.

[18] Pukanszky B, Fekete E. Adhesion and surface modifica-

tion in mineral fillers in thermoplastics. Raw materials

and processing. Adv Polym Sci 1999;139:109–53.

[19] Maurer FHJ, Schoffeleers HM, Kosfeld R, Uhlenbroich

T. Analysis of polymer–filler interaction in filled polyeth-

ylene. In: Hayashi T, Kawata K, Umekawa S, editors.

Progress in science and engineering of composites, ICCM-

IV, Tokyo, 1982. p. 803–9.

[20] Akay G. Flow induced polymer–filler interactions bound

polymer properties and bound polymer-free polymer

phase separation and subsequent phase inversion during

mixing. Polym Eng Sci 1990;30:1361–72.

[21] Mansfield KF, Theodorou DN. Atomistic simulation of a

glassy polymer/graphite interface. Macromolecules 1991;

24:4295–309.

[22] Iisaka K, Shibayama K. Mechanical a-dispersion and

interaction in filled polystyrene and polymethyl-methac-

rylate. J Appl Polym Sci 1978;22:3135–43.

[23] Kolarık J, Hudecek S, Lednicky F. Uber die mechanischen

EigenschaftenvonVerbundenausPolyurethanelastomeren


und vernetzten polymeren Fullstoffen. Faserforsch Textil-

techn 1978;29:51–6.

[24] Kolarık J, Hudecek S, Lednicky F, Nicolais L. Temper-

ature dependence of reinforcement in the composites

polyurethane rubber-crosslinked polymeric filler. J Appl

Polym Sci 1979;23:1553–64.

[25] Pukanszky B, Tudos F. Indirect determination of inter-

phase thickness from the mechanical properties of

particulate filled polymers. In: Ishida H, editor. Con-

trolled interphases in composite materials. New

York: Elsevier; 1990. p. 691–700.

[26] Jones FR. Interfacial aspects of glass fibre reinforced

plastics. In: Jones FR, editor. Interfacial phenomena in

composite materials �89. London: Butterworths; 1989. p.

25–32.

[27] Scholtens BJR, Brackman JC. Influence of the film former

on fiber–matrix adhesion and mechanical properties of

glass–fiber reinforced thermoplastics. J Adhesion

1995;52:115–29.

[28] Day RJ, Hewson KD, Lovell PA. Surface modification

and its effect on the interfacial properties of model

aramid-fibre/epoxy composites. Compos Sci Technol

2002;62:153–66.

[29] Plueddemann EP. Silane coupling agents. New

York: Plenum; 1982.

[30] Danyadi L, Gulyas J, Pukanszky B. Coupling of carbon

fibers to polycarbonate: surface chemistry and adhesion.

Compos Interfaces 2003;10:67–76.

[31] Tjong SC, Xu SA, Li RKY, Mai YW. Short glass fiber-

reinforced polyamide 6,6 composites toughened with

maleated SEBS. Compos Sci Technol 2002;62:

2017–27.

[32] Williams JG, James MR, Morris WL. Formation of the

interphase in organic-matrix composites. Composites

1994;25:757–62.

[33] Chand S. Carbon fibers for composites. J Mater Sci

2000;35:1303–13.

[34] Tang LG, Kardos JL. A review of methods for improving

the interfacial adhesion between carbon fiber and polymer

matrix. Polym Compos 1997;18:100–13.

[35] Akovali G, Dilsiz N. Studies on the modification of

interphase/interfaces by use of plasma in certain poly-

mer composite systems. Polym Eng Sci 1996;36:

1081–6.

[36] Wade GA, Cantwell WJ, Pond RC. Plasma surface

modification of glass fibre-reinforced nylon-6,6 thermo-

plastic composites for improved adhesive bonding. Inter-

face Sci 2000;8:363–73.

[37] Cech V, Prikryl R, Balkova R, Grycova A, Vanek J.

Plasma surface treatment and modification of glass fibers.

Composites 2002;33A:1367–72.

[38] Montes-Moran MA, Martınez-Alonso A, Tascon JMD,

Young RJ. Effects of plasma oxidation on the surface and

interfacial properties of ultra-high modulus carbon fibres.

Composites 2001;32A:361–71.

[39] Huang YD, Liu L, Qiu JH, Shao L. Influence of

ultrasonic treatment on the characteristics of epoxy resin

and the interfacial property of its carbon fiber composites.

Compos Sci Technol 2002;62:2153–9.

[40] Bledzki AK, Gassan J. Composites reinforced with

cellulose based fibres. Prog Polym Sci 1999;24:221–74.

[41] Li Y, Mai YW, Ye L. Sisal fibre and its composites: a

review of recent developments. Compos Sci Technol

2000;60:2037–55.

[42] Keener TJ, Stuart RK, Brown TK. Maleated coupling

agents for natural fibre composites. Composites 2004;

35A:357–62.

[43] George J, Sreekala MS, Thomas S. A review on interface

modification and characterization of natural fiber rein-

forced plastics composites. Polym Eng Sci 2001;

41:1471–85.

[44] Wypych G. Handbook of fillers. Toronto: ChemTec

Publishing; 1999.

[45] Rothon RN. Particulate-filled polymer compos-

ites. Shawbury: Rapra; 2003.

[46] Hornsby PR. Rheology, compounding and processing

of filled thermoplastics. Adv Polym Sci 1999;139:

155–217.

[47] Fekete E, Molnar Sz, Kim GM, Michler GH, Pukanszky

B. Aggregation, fracture initiation and strength of PP/

CaCO3 composites. J Macromol Sci Phys 1999;B38:

885–99.

[48] Ren Z, Shanks RA, Rook TJ. Rheology of highly filled

polypropylenes prepared with surface treated fillers.

Polym Polym Compos 2003;11:541–50.

[49] Domka L, Foltynowicz Z, Jurga S, Kozak M. Influence

of silane modification of kaolins on physico-mechanical

and structural properties of filled PVC composites. Polym

Polym Compos 2003;11:397–406.

[50] Shakeri AR, Hashemi SA. Effect of coupling agents on

mechanical properties of HDPE/wheat straw composites.


[51] Trotignon JP, Verdu J, De Boissard R, De Vallois A.

Polypropylene–mica composites. In: Sedlacek B, editor.

Polymer composites. Berlin: Walter de Gruyter; 1986.

p. 191–8.

[52] Demjen Z, Pukanszky B. Effect of surface coverage

of silane treated CaCO3 on the tensile properties of

polypropylene composites. Polym Compos 1997;18:

741–7.

[53] Pukanszky B, Voros Gy. Mechanism of interfacial

interactions in particulate filled composites. Compos

Interfaces 1993;1:411–27.

[54] Moreiras G. Baby boom market for fillers. GCC in

microporous films. Ind Miner 2001(6):29–33.

[55] Scott C, Ishida H. Rubber–filler interaction effects on the

solid state dynamic mechanical properties of polyethyl-

ene/EPDM/calcium carbonate composites. Polym Com-

pos 1992;13:237–43.

[56] Guschl PC, Otaigbe JU. An experimental study of

morphology and rheology of ternary Pglass–PS–LDPE

hybrids. Polym Eng Sci 2003;43:1180–96.

[57] Pukanszky B, Tudos F, Kolarık J, Lednicky F. Ternary

composites of polypropylene, elastomer and filler: anal-

ysis of phase structure formation. Polym Compos

1990;11:98–104.

[58] Molnar Sz, Pukanszky B, Hammer CO, Maurer FHJ.

Impact fracture study of multicomponent polyethylene

composites. Polymer 2000;41:1529–39.

[59] Jeong HK, Rooney M, David DJ, MacKnight WJ,

Karasz FE, Kajiyama T. Miscibility of polyvinyl buty-

ral/nylon-6 blends. Polymer 2000;41:6003–13.


[60] Mortensen K. Small-angle X-ray and neutron scattering

studies from multiphase polymers. Curr Opin Solid State

Mater Sci 1997;2:653–60.

[61] Huang HL, Goh SH, Wee ATS. Miscibility and interac-

tions in poly(2,2,3,3,3,-pentafluoropropyl methacrylate-

co-4-vinylpyridine)/poly(p-vinylphenol) blends. Polymer

2002;43:2861–7.

[62] Kurosu H, Chen Q. Structural studies of polymer blends

by solid state NMR. Ann Rep NMR Spectroscopy

2004;52:167–200.

[63] Haggard KW, Paul DR. Blends of high temperature

copolycarbonates with bisphenol-A-polycarbonate and

a copolyester. Polymer 2004;45:2313–20.

[64] Bucknall CB, Arrighi V. Neutron scattering and polymer

blends. In: Paul DR, Bucknall CB, editors. Polymer

blends, vol. 1. New York: Wiley; 2000. p. 349–78.

[65] Gestoso P, Brisson J. Towards the simulation of

poly(vinyl phenol)/poly(vinyl methyl ether) blends by

atomistic molecular modeling. Polymer 2003;44:2321–9.

[66] Shi T, Wen G, Jiang W, An L, Li B. Monte Carlo

simulation of miscibility of polymer blends with repulsive

interactions: effect of chain structure. Eur Polym J

2003;39:551–60.

[67] Koning C, van Duin M, Pagnoulle C, Jerome R.

Strategies for compatibilization of polymer blends. Prog

Polym Sci 1998;23:707–57.

[68] Markarian J. Compatibilizers find the right blend. Plast

Addit Compd 2004;6:22–5.

[69] Paul DR, Bucknall CB. Polymer blends. New York:

Wiley; 2000.

[70] Fekete E, Pukanszky B, Peredy Z. Mutual correlations

between parameters characterizing the miscibility, struc-

ture and mechanical properties of polymer blends. Angew

Makromol Chem 1992;199:87–101.

[71] Fekete E, Foldes E, Damsits F, Pukanszky B. Interac-

tion–structure–property relationships in amorphous poly-

mer blends. Polym Bull 2000;44:363–70.

[72] Buki L, Gonczy E, Fekete E, Hellmann GP, Pukanszky

B. Miscibility–property correlations in blends of glassy

amorphous polymers. Macromol Symp 2001;170:9–20.

[73] Foldes E, Pukanszky B. Miscibility–structure–property

correlation in blends of ethylene–vinyl alcohol copolymer

and polyamide 6/66. J Colloid Interface Sci, in press

[doi:10.1016/j.cis.2004.08.175].

[74] St-Pierre N, Favis BD, Ramsay BA, Ramsay JA,

Verhoogt. Processing and characterization of thermoplas-

tic starch/polyethylene blends. Polymer 1997;38:647–55.

[75] Kim M. Evaluation of degradability of hydroxypropy-

lated potato starch/polyethylene blend film. Carbohydr

Polym 2003;54:173–81.

[76] Rodriguez-Gonzalez FJ, Ramsay, Favis BD. High per-

formance LDPE/thermoplastic starch blends: a sustain-

able alternative to pure polyethylene. Polymer 2003;

44:1517–26.

[77] Mano JF, Koniarova D, Reis RL. Thermal properties of

thermoplastic starch/synthetic polymer blends with poten-

tial biomedical applicability. J Mater Sci Mater Med

2003;14:127–35.

[78] Ha CS, Cho WJ. Miscibility, properties, and biodegrad-

ability of microbial polyester containing blends. Prog

Polym Sci 2002;27:759–809.

[79] Lu X, Zhang MQ, Rong MZ, Yue DL, Yang GC. The

preparation of self-reinforced sisal fiber composites.


[80] Pukanszky B, Fekete E. Aggregation tendency of partic-

ulate fillers: determination and consequences. Polym

Polym Compos 1998;6:313–22.

[81] Rong MZ, Zhang MQ, Zheng YX, Zeng HM, Friedrich

K. Improvement of tensile properties of nano-SiO2/PP

composites in relation to percolation mechanism. Polymer

2001;42:3301–4.

[82] Rong MZ, Zhang MQ, Pan SL, Lehmann B, Friedrich K.

Analysis of the interfacial interactions in polypropylene/

silica nanocomposites. Polym Int 2004;53:176–83.

[83] Schmidt H. New type of non-crystalline solids between

inorganic and organic materials. J Non-Cryst Solids

1985;73:681–91.

[84] Mark JE. Ceramic-reinforced polymers and poly-

mer-modified ceramics. Polym Eng Sci 1996;36:

2905–20.

[85] Kickelbick G. Concepts for the incorporation of inor-

ganic building blocks into organic polymers on a nano-

scale. Prog Polym Sci 2003;28:83–114.

[86] Matejka L, Dusek K, Plestil J, Kriz J, Lednicky F.

Formation and structure of the epoxy–silica hybrids.

Polymer 1998;40:171–81.

[87] Matejka L, Dukh O, Meissner B, Hlavata D, Brus J,

Strachota A. Block copolymer organic–inorganic net-

works. Formation and structure ordering. Macromole-

cules 2003;36:7977–85.

[88] Lichtenhan JD, Otonari YA, Carr MJ. Linear hybrid

polymer building blocks: methacrylate-functionalized

polyhedral oligomeric silsesquioxane monomers and

polymers. Macromolecules 1995;28:8435–7.

[89] Matisons J. POSS: from macromonomers to polymers.

Presented at the 11th Intl Conf Polym Mater, Halle,

Germany, September 29–October 1, 2004.

[90] Ribot F, Banse F, Diter F, Sanches C. Hybrid organic–

inorganic supramolecular assemblies made from butyltin

oxo–hydroxo nanobuilding blocks and dicarboxylates.

New J Chem 1995;19:1145–53.

[91] Biro LP, Lazarescu SD, Thiry PA, Fonseca A, BNagy J,

Lucas AA, Lambin P. Scanning tunneling microscopy

observation of tightly wound, single-wall coiled carbon

nanotubes. Europhys Lett 2000;50:494–500.

[92] Biro LP, Bernardo CA, Tibbets GG, Lambin P. Carbon

filaments and carbon nanotubes common origins, differ-

ing applications? Dordrecht: Kluwer; 2001.

[93] Ajayan PM, Schadler LS, Giannaris C, Rubio A. Single-

walled carbon nanotube–polymer composites: strength

and weakness. Adv Mater 2000;12:750–3.

[94] Barber AH, Cohen SR, Kenig S, Wagner HD. Interfacial

fracture energy measurements for multi-walled carbon

nanotubes pulled from a polymer matrix. Compos Sci

Technol 2004;64:2283–9.

[95] Gong X, Liu J, Baskaran S, Voise RD, Young JS.

Surfactant-assisted processing of carbon nanotube/poly-

mer composites. Chem Mater 2000;12:1049–52.

[96] Gojny FH, Schulte K. Functionalization effect on the

thermo-mechanical behaviour of multi-wall carbon nano-

tube/epoxy-composites. Compos Sci Technol 2004;64:

2303–8.

http://dx.doi.org/10.1016/j.cis.2004.08.175


[97] Namilae S, Chandra N, Shet C. Mechanical behavior of

functionalized nanotubes. Chem Phys Lett 2004;387:

247–52.

[98] Dzenis Y. Spinning continuous fibers for nanotechnology.

Science 2004;304:1917–9.

[99] Berghoef MM, Vancso GJ. Transparent nanocomposites

with ultrathin, electrospun nylon-4,6 fiber reinforcement.

Adv Mater 1999;11:1362–5.

[100] Usuki A, Kojima Y, Kawasumi M, Okada A, Fukushima

Y, Kurauchi T, et al. Synthesis of nylon 6-clay hybrid. J

Mater Res 1993;8:1179–84.

[101] Kojima Y, Usuki A, Kawasumi M, Okada A, Fukushima

Y, Kurauchi T, et al. Mechanical properties of nylon 6–

clay hybrid. J Mater Res 1993;8:1185–9.

[102] Giannelis EP. Polymer layered silicate nanocomposites.

Adv Mater 1996;8:29–35.

[103] Alexandre M, Dubois P. Polymer-layered silicate nano-

composites: preparation properties and uses of a new class

of materials. Mater Sci Eng R 2000;28:1–63.

[104] Simha Ray S, Okamoto M. Polymer/layered silicate

nanocomposites: a review from preparation to processing.

Prog Polym Sci 2003;28:1539–641.

[105] Pinnavaia TJ, Beall GW. Polymer–clay nanocompos-

ites. New York: John Wiley; 2001.

[106] Fischer H. Polymer nanocomposites from fundamental

research to specific applications. Mater Sci Eng

2003;23C:763–72.

[107] Ishida H, Campbell S, Blackwell J. General approach to

nanocomposite preparation. ChemMater 2000;12:1260–7.

[108] Sheng N, Boyce MC, Parks DM, Rutledge GC, Abes JI,

Cohen RE. Multiscale micromechanical modeling of

polymer/clay nanocomposites and the effective clay par-

ticle. Polymer 2004;45:487–506.

[109] van Ess M. Polymer–clay nanocomposites. The impor-

tance of particle dimensions. Ph.D. Thesis, Technical

University Delft, 2001.

[110] Wang H, Zeng C, Elkovitch M, Lee LJ, Koelling KW.

Processing and properties of polymeric nano-composites.

Polym Eng Sci 2001;41:2036–46.

[111] Pozsgay A, Csapo I, Szazdi L, Pukanszky B. Preparation,

structure, and properties of PVC/montmorillonite nano-

composites. Mater Res Innov 2004;8.3:138–9.

[112] Kaempfer D, Thomann R, Mulhaupt R. Melt compound-

ing of syndiotactic polypropylene nanocomposites

containing organophilic layered silicates and in situ

formed core/shell nanoparticles. Polymer 2002;43:

2909–16.

[113] Pukanszky B, Fekete E, Tudos F. Surface tension and

mechanical properties in polyolefin composites. Makro-

mol Chem Macromol Symp 1989;28:165–86.

[114] Fox HW, Hare EF, Zismann WA. Wetting properties of

organic liquids on high energy surfaces. J Phys Chem

1955;59:1097–106.

[115] Stewart R. Nanocomposites. Microscopic reinforce-

ments boost polymer performance. Plast Eng 2004(5):

22–30.

[116] Gomes ME, Ribeiro AS, Malafaya PB, Reis RL, Cunha

AM. A new approach based on injection moulding to

produce biodegradable starch-based polymeric scaffolds:

morphology, mechanical and degradation behaviour.

Biomaterials 2001;22:883–9.

[117] Shin H, Jo S, Mikos AG. Biomimetic materials for tissue

engineering. Biomaterials 2003;24:4353–64.

[118] Drury JL, Mooney DJ. Hydrogel for tissue engineering:

scaffold design variables and applications. Biomaterials

2003;24:4337–51.

[119] Atala A, Mooney DJ. Synthetic biodegradable polymer

scaffolds (tissue engineering). Boston: Birkhauser; 1997.

[120] Blunk T, Gopferich A, Tessmar J. Biomimetic polymers.

Biomaterials 2003;24:4335.

[121] Growth opportunities in carbon fiber market 2004–2010.

<www.e-polymers.com>.

[122] Markarian J. Additive developments aid growth in wood–

plastic composites. Plast Addit Compd 2002(11):18–21.

[123] Marsh G. Next step for automotive materials. Mater

Today 2003(11):35–43.

[124] Pritchard G. Two technologies merge: wood plastic

composites. Plast Addit Compd 2004(7/8):18–21.

http://www.e-polymers.com

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