Chitosan Derivatives as Consolidation Materials the 7th Int Symposium Braila

8/13/2019 Chitosan Derivatives as Consolidation Materials the 7th Int Symposium Braila

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Gheorghe Asachi Technical University of Iasi,

Romania

The 7th International Symposium on Advanced Technologies

for the pulp and Paper Industry, Braila, September 3 5, 2013

CHITOSAN DERIVATIVES AS CONSOLIDATION

MATERIALS IN PAPER HERITAGE CONSERVATION

Elena Bobu, F.Ciolacu, P. Obrocea, Raluca Nicu, T. Balan


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This research was performed in the frame of PN-II project:

Developing Non-conventional Materials and Cold Plasma

Techique for Sustainable Solutions in Paper HeritageConservation - PAPHERCON

Project number: 221/ 2012

More information can be found at: www.paphercon.ro

Study framework


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Presentation outline

Chitosan derivatives as consolidation materials

Features of chitosan as papermaking bio additive

Synthesis of chitosan derivatives with specific functionalitiesChitosan derivatives evaluation in paper consolidation

Paper heritage conservation

Documentary heritage deterioration

Paphercon project: Concept and objectives


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Deterioration of collections from museums/archives is attributed to:

Internal factors the materials from which the objects are made

External factors the environment surrounding the object

Paper Heritage Deterioration

(Reyden, van der D., JAIC, 31, 1, 1992)

The combined action ofthese factors leads to

changes in the preservation

state of paper documents:

Loss of structural and

compositional integrity,

and a decrease in physical

and mechanical resistanceproperties

In Romania, 50% of the National Archive Fund needs to be

restored in the next 15-20 years

External factors:

temperature, humidity, light, pollutant gases(SO2, NOx, NH3, ozone, etc.), dust,

microorganisms, social factors, etc.2 x 3

Internal factors:

fibre type, pH and acidity/alkalinity,sizing agents, metal ions, cellulose

degradation products


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Paper Ageing

(Banks, P., Conservation in Archives-International Symposium, Paris,1989, p. 7788)

Natural ageing processes are causing major losses of paperheritage from archives and libraries

Paper permanence (aging resistance): the ability of paper to last at leastseveral hundred years without significant deterioration under normalconditions of storage and use in libraries and archives (ANSI/NISO Z39.48-1992)

Main paper ageing mechanisms:

oHydrolytic processesmainly due to temperature,acidity (pH) and moisture content

oOxidative processesmainly due to oxygen andpollutants (O3, NOx, etc.) in the environmental air

Under normal conditions of storage, theseprocesses are very slow, but inevitably they stilllead to well-known aging effects:

paper yellows, loses strength and becomes brittle


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A reliable procedure for the evaluation of conservation

treatments is needed:

The conservation of paper documents aims to:

orepair the degradation they underwent,oextend their lifespan by protecting against further degradation.

Conservation methods rely on curative and restoration treatments

(disinfection, wet cleaning, consolidation) that produce complex

interactions with the components of the paper support.

These interactions complicate the evaluation of conservation treatment

effectiveness and durability and could lead to physical and chemical

alterations and even to the loss of paper heritage objects.

Paphercon Concept

Paphercon project will develop a new procedure to evaluate the

conservation treatments in an integrated manner, taking into

account the whole life cycle of the paper document.


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It is imperative to develop new and more sustainable

consolidation materials:

Consolidation aims at restoring the structural strength and integrity of papersupport by applying different adhesives. Cellulose ethers (CMC and MC)

are the main adhesives used for paper documents consolidation due to

their compatibility with paper substrate and effectiveness in improving

mechanical strength.

However, cellulose ethers are hydrophilic materials that increase water

absorption in paper support, which later could intensify the hydrolytic

degradation processes and microbial contamination.

Paphercon will provide considerable innovation in the field of

consolidation materials by developing chitosan derivatives and nano-

composite coating formulas with multiple functionalities in paper

conservation.

Paphercon Concept


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Paphercon Concept

An ecological solution for paper documents cleaning and

decontamination is needed:

In restoration treatments, paper documents are subjected to cleaning

and decontamination prior to consolidationoCleaning methods employ organic solvents, liquid nitrogen, water, or ascalpel-blade knife to remove dust, deterioration products, stains,adhesives from previous restorations, etc.

oIn decontamination toxic chemicals or physical treatments are used todestroy viable microorganisms

Both these processes produce side effects that are insufficiently studiedand could be dangerous for both the object and the restorer.

Paphercon proposes the application of cold HF (high frequency) after-glow plasma treatment as a fast, soft and ecological solution for thecleaning and microbial decontamination of paper heritage items.


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Paphercon Concept

The integration of cleaning, decontamination and

consolidation in sustainable conservation methods:

The research proposed by Paphercon project will generate moreknowledge on fundamental processes occurring when chitosan-basedfilms and plasma discharge interacts with paper.

The results of several individual studies will be analised in a criticalmanner in order

to develop and implement a new and innovative conservation

method by combining cold HF plasma treatments and multifunctional

coatings based on chitosan derivatives .


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Paphercon Objectives

General objective of project is to develop, implement and

validate an integrated solution for sustainable and accurate

conservation of paper heritage objects

Scientific objectives are:

To elaborate a reliable procedure for the evaluation of conservation

treatments, in order to provide a more scientific approach in paper

heritage conservationTo develop new materials for the consolidation of paper heritage

items, which would bring specific functionalities to paper surfaces, such as

anti-microbial activity and barrier to water vapors, aiming at improving the

efficiency and durability of conservation process.

To innovate current cold HF plasma technique by adding a special

chamber for after-glow discharge in order to allow a soft and flexible

treatment, adaptable to paper particularities.


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Paphercon Expected Benefits

A long term objective of the project is to improve the

sustainability of paper conservation, based on:

A consistent increase of conservation yield

means areduction of time for conservation treatment (about 10 times),which could contribute substantially to saving more culturalpaper heritage.

Reducing the toxicity of the working environment inconservation through to the elimination of the cleaning anddecontamination chemicals.

Application of new biopolymer-based conservationmaterials, with additional functionalities beside structuralconsolidation (i.e. antimicrobial and oxygen/water barrier)that will slow considerably the action of degradation factors

and will extend the life of documentary heritage.


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Chitosan derivatives as consolidation materialsFeatures of chitosan as papermaking bio additive

Synthesis of chitosan derivatives with specific functionalities

Chitosan derivatives evaluation in paper consolidation

Presentation online





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Features of Chitosan Bioadditive

Chitosan can be considered an attractive alternative fordeveloping bioadditives with applications in papermaking:

It is obtained from renewable resources

It is biodegradable

It is biocompatible

It is non-toxic

It has antimicrobial properties

OO

*

OO

HO

NH2

O

OH

OH

NH2HO

O

OO

HO

NH2

O*

OH

OH

NHHO

DA

C

CH3

O

The amino and hydroxyl groups of chitosan offer the

possibility to obtain a wide variety of derivatives through

chemical modifications


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Due to its unique combination of properties, chitosan can

have more than one function in paper conservation:

oDry strength additive and adhesive chitosan is able to form

hydrogen bonds with cellulose fibers, improving the surface and

internal paper strength

oBarrier additive chitosan is nontoxic and has good film

forming properties, thus it can be used in coating formulations to

develop barrier to water and gases

oAntimicrobial additive chitosan displays antibacterial and

antifungal properties, which could be exploited in conservation

and restoration to improve paper permanence

Chitosan as Bioadditive in Conservation


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Water Soluble Chitosan Derivatives

The main limitation to chitosan application in conservation is

the lack of water solubility at neutral pH Solution: chemical

modification to obtain water soluble derivatives

Chitosan possess functional groups available forchemical reactions to generate new functionalities:

amino function provides potential for the

acetylation, alkylation, quaternization, grafting

and metals chelation;

hydroxyl groups give various reactions,

such as O-acetylation (e.g. O-carboxymethyl

chitosans), H-bonding with polar atoms,grafting, etc.

In the Paphercon project, chitosan is modified through N-alkylation and

quaternization reactions at the amino group and carboxymethylation at the

hydroxyl groups.


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Alkyl Chitosan

Alkyl-chitosan was synthesized through a reductive amination

reaction, using aliphatic aldehydes

Why alkyl chitosan (AlCh)?

oAlCh can be easily converted in water soluble salts

oAlCh has ability to improve paper strength by similar mechanisms of

other polysacharides used in conservation (CMC, MC,etc.)

oAlCh films can decrease hydrophilic character of paper surface as a

function of alkyl chain length and substitution degree

o

AlCh has never been tested before in papermaking of in paperdocuments conservation


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Quaternary Chitosan

Quaternary derivatives were synthesized by the O-and N-acylation of chitosan with Quat-188

Why quaternary chitosan (QCh)?

oQCh is water soluble and has cationic charge over total pH range

oQCh has anti-microbial properties which could be improved by

controlling the substitution degree.

oQCh has high affinity for cellulose fibre surface and H-bonding

potential and thus, it can contribute to the improvement of paper strength

oQCh has never been evaluated before in paper documents conservation

Cl

CH2

CH

CH2

N

CH3

CH3

CH3

OH

NaOH,10% (w/w)

pH=8,5-8,8H2C C

H

H2C N

CH3

CH3

CH3

O

ClCl

O

OO

O

OH

NHHO

O

NH

HO O

DA

CO

CH3

NaI

H2C

CH

H2C

N

CH3CH3

CH3

OH

Cl

H2C

CH

H2C

N

CH3CH3

CH3

OH

Cl

O

OO

O

OH

NH2HO

OH

NH

HO O

DA

CO

CH3

H2C CH

H2C N

CH3

CH3

CH3

O

Cl


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Carboxymethyl Chitosan

Carboxymethyl-chitosan was synthesized under alkaline

conditions by etherification with monochloroacetic acid,

Why Carboxymethyl-chitosan (CMCh)?

oCMCh is fully soluble in water giving solutions with slight alkaline pH

oCMCh solutions present quite stable properties, which results in good film

forming properties

oCMCh molecule has amphoteric character, which confers high complexation

capacity

oCMCh has ability to improve paper strength by mechanisms similar toother polysaccharides used in conservation (CMC, MC,etc.)


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Presentation outline

Chitosan derivatives as consolidation materialsFeatures of chitosan as papermaking bio additive

Synthesis of chitosan derivatives with specific functionalities

Chitosan derivatives evaluation in paper consolidation





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The investigations that will be presented here are part of an extended

study in Paphercon project, with the following general objective:

To develop chitosan derivatives with specific functionalities in

the conservation of paper heritage, such as the bonding/adhesive

potential, hydrophobization, and anti-microbial activity.

Chitosan Derivatives as Strength Additives

Experimental work tasksoThe synthesis and characterization of the three types of chitosan

derivatives: Akyl-, Quaternary-, and Carboxymethyl-chitosan;

oPreparation of handsheets as support for polymer coating application;

oPreparation of polymer solutions and application on paper surface

oCharacterization of surface treated paperby three groups of properties:

Physical-mechanical properties

Physical-chemical propertiesMicrobiological properties

Research objective


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Fibrous materials:Bleached softwood Kraft pulp (BSKP)Bleached hardwood Kraft pulp (BHKP)BSKP:BHKP=30:70

Coating polymers:Chitosan derivatives QCh, CMCh, AlCh,Native chitosans HMW, MMWa, MMWb

Experimental workMaterials

Main characteristics of native and modified chitosans

Native chitosan Characteristics Chitosan derivative Characteristics

Ch HMW(High Molecular Weight)

Mw = 7.56105 g/mol

DA = 20.8 %

pH = 3.94

QCh(Quaternary chitosan)

pH = 6.76

S = 92,3%

DS = 0,92

Ch MMWa(Medium Molecular Weight-shrimp)

Mw

= 4.347105 g/mol

DA = 12.07 %

pH = 3.94

CMCh(Carboxymethyl chitosan)

pH = 7.65

S = 93.6%

DS = 0,98

Ch MMWb(Medium Molecular Weight-crab)

Mw = 2.375105 g/mol

DA = 13.5 %

pH = 3.96

AlCh(Alkyl chitosan)

pH = 7.03

S = 99.7%

DS = 0,037

Legend: DA-Degree of Acetylatation; DS-Degree of Substitution; pH of 5 g/L polymer solutions; S water solubility, at25oC.


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Experimental work

Methods

Fibrous material preparation:

-Beating to 300 SR

-Mixing BSKP:BHKP=30:70

Laboratory paper sheetsformation641 g/m2

Surface coating

Coating solution preparation:

Polymer, 5g/L

Valley Holender

Operations: Apparatus:

Rapid-Kthen

Rod Meyer

Lab Blender

Fibrous material preparation:

-Beating to 300 SR

-Mixing BSKP:BHKP=30:70

Laboratory paper sheetsformation641 g/m2

Surface coating

Coating solution preparation:

Polymer, 5g/L

Valley Holender

Operations: Apparatus:

Rapid-Kthen

Rod Meyer

Lab Blender


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Experimental work

Evaluation of physical and mechanical properties

Load Elongation Properties: tensile index

(TI, N.m/g), elongation at break (Fmax, %),

tensile energy absorption (TEA, J/m2) were

determined according to the constant strain

gradient method (ISO 1924-2-1994), using a

Zwick testing machine

Folding endurance (no. of double folds)was tested using a schopper type tester

according to standard method ISO 5626-

1993, TAPPI T 423 om-89.

All samples were conditioned for 24 h in astandard atmosphere (at 23 C and 50% RH)

according to standard method (SR EN 20187

-1996).


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Tensile Index

40

50

60

70

80

90

100

110

Blank QCh CMCh AlCh

TensileIndex,N

m/g

Corresponding native chitosan Modif ied chitosan

QCh - 0.92 Ch HMW

CMCh-0.98 Ch MMWa

AlCh -0.037 Ch MMWb

In the case of native chitosans, TI increases with MW, but there is nolinear dependence due to the influence of chitosan origin

The TI decreases by the chemical modification of chitosan, but it is stillhigher than blank sample and standard deviation is reduced consistently

Standard deviation, N.m/g

Substitution degree

could be linked to

MW decrease andfilm uniformity

increase


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Breaking Elongation

oSurface treatments with both native and modified chitosans lead to aconsistent increase of paper elongation at break, which is very important fortheir application in paper heritage consolidation.

0

1

2

3

4

5

6

Blank QCh CMCh AlCh

Elongationatbreak,

%

Corresponding native chitosan Modified chitosan

Break elongation

increases with 80 - 90%

for native chitosan and

with 50-70% for chitosan

derivatives

QCh - 0.92 Ch HMW

CMCh-0.98 Ch MMWa

AlCh -0.037 Ch MMWb

Standard deviation, %


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Tensile Energy Absorption

50

80

110

140

170

200

230

Blank QCh CMCh AlCh

Tensileenergyabsorp

tion,

J/m

2

Corresponding nat ive chitosan Modified chitosan

TEA,

J/m2

oTEA is the work required to rupture the strip, and thus equals the area under thecurve (see diagram). It is expressed as energy per unit area of sample tested (inJ/m2)..

oTEAis a characteristic that helps describe paper behaviour under the complex stressassociated with document handling

All chitosan derivativesshown a significant increase

of TEA, with up to 90%,demonstrating the elasticnature of the reinforcementtreatment.

Standard deviation, J/m2


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Folding Endurance

0

200

400

600

800

1000

1200

1400

1600

Blank QCh CMCh AlChFoldingendurance,no.ofdoub

lefolds

Corresponding native chitosan Modified chitosan

Folding endurance is the most used property for assessing the effects of ageingprocess and the conservation treatments applied to paper documents.

oThe folding endurance of surface treated papers increased up to 6 times fornative chitosans and up to two times for modified chitosans , the main influence

factors being molecular weight of native chitosan and type of chemicalmodification.

QCh - 0.92 Ch HMW

CMCh-0.98 Ch MMWa

AlCh -0.037 Ch MMWb

Standard deviation, no. of double folds


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Conclusions

oSurface treatments with native chitosan produced an important

increase in mechanical resistance properties, strongly

influenced by polymer source and molecular weight.

oThe main disadvantages of native chitosan are the lack of

water solubility at neutral pH, high poly-dispersity and poor filmuniformity.

oChemical modifications of chitosan provide the means to

overcome these drawbacks allowing the synthesis of derivativesthat are water-soluble at neutral pH and with improved film-

forming properties.


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Conclusions

oChitosan derivatives produce a lower increase of strength

properties, but more uniform films than chitosan, which result inlower standard deviations for all mechanical characteristics.

oThe most important aspects regarding the application potential

of chitosan derivatives in restoration treatments are:Water solubility at neutral/slightly alkaline pH

Good film forming properties

The elastic reinforcement of paper structure, with animportant increase in elongation, tensile energy absorption

and folding endurance, which improves the ability of paper

to withstand handling.


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Acknowledgments

The UEFISCDI is acknowledged for funding Paphercon

project from the PN II Programme- Project PCCA Type 2,under Grant Agreement n 221/2012


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Contact information:

ELENA BOBU

Gheorghe Asachi Technical University of Iasi

Dimitrie Mangeron No. 71 Iasi, RO- 700050

[email protected]

Chitosan Derivatives as Consolidation Materials the 7th Int Symposium Braila

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