Characterization of Nanocomposites by TMA

Prepared by: Bademaw Abate

Introduction Polymer nanocomposites (PN) are polymer

matrices(thermoplastics, thermosets or elastomers) that have been reinforced with small quantities of nano-sized particles, preferably characterized by high aspect ratios, such as layered silicates and carbon nanotubes.

Nanomaterials have been added to polymers with the aim of creating high–performance lightweight materials with combinations of properties tailored for specific commercial applications.

TMA is a highly sensitive technique for the measurement of expansion and contraction of cross-linked or filled materials, including Nano composites

Experimental procedures and Methods• The thermosetting phenolic resin with ∼9% hexamethylenetetramine (HMTA) as curing agent was obtained from Hexion• Specialty Chemicals Pty Ltd (Fig. 1). Synthetic graphite nanoplatelets• (SG) with average thickness of 100 nm and diameters of• 1–3 m were supplied by Asbury Graphite Mills, and are products• of the heat treatment of carbonaceous materials with 99%• purity and density of 1.75 g/cm3, and have highly exfoliated and• crystalline structure (see Supplementary Data). The composition• of SG/phenolic FGNs was designed by considering the high thermal• and mechanical properties of SG and low thermal conductivity• of the phenolic. To study the effect of SG distribution patterns on• thermomechanical and viscoelastic properties, four different layered• functionally graded nanocomposites as well as non-graded• nanocomposites with the same geometry and SG content were• prepared.• The SG nano-platelets were dried in a vacuum oven at 40 ◦C• for 24 h to remove moisture contents. The powder mixtures of• SG and phenolic resin with 5,10, and 20 wt% SG contents were• ball milled (8000M, Mixer/Mill, Maker, Spex, USA) for 1 h to• ensure homogeneous dispersion of SG within the phenolic resin

• All samples were fabricated using• compression molding and powder stacking technique. Premixed• composite powders of certain SG contents were settled in a die of a• hot press in a desired sequence using a stacker device. The graded• stacks of composite powders heated up to 130 ◦C for 10 min and• then hot pressed at 180 ◦C and 15 MPa for 10 min and finally cooled• down. A range of compositions were made. As illustrated in Fig. 2,• FGN-1 has the concentration of SG decreasing from the outer surfaces• to the core from 20 to 0 wt%. In contrast, FGN-2 has 20 wt%• SG in the c

Results and discussion• Thermomechanical and viscoelastic properties

Creep-recovery response from different configurations of functionally graded nanocomposites (FGNs), non-graded nanocomposites (NGNs), and phenolic.

Creep-recovery response from different configurations of functionally graded nanocomposites (FGNs), non-graded nanocomposites (NGNs), and phenolic.

Variation of coefficient of thermal expansion (CTE) across the thickness (a) FGN-1, (b) FGN-2, (c) FGN-3, and (d) FGN-4.

Coeffient of thermal Expansion

Thermo mechanical analysis (TMA), done to determine the coefficient of linear thermal expansion (CLTE) of the composites containing unmodified MWCNTs, was

carried out on a Mettler Toledo TMA/SDTA841e with a ball–point probe (3.0 mm). Measurements were performed between two quartz disks (d=

6 mm) under a nitrogen gas flow (30 ml/min) between 40 and 120 °C with a heating rate of 5 °C/min and normal load of 0.05 N. The TMA program included two heating–cooling cycles, and

the CLTE was recorded from the second heating.

Glass transition temperature of nanocomposites based on amorphouspoly(ethylene terephthalate) (PETg) and organically modified

montmorillonites.

Conclusion Thermo mechanical and viscoelastic properties are highly dependent on the microstructural gradient patterns. Nanocomposites with high concentration of SG on the top and

bottom surfaces and low in the core, showed better thermo-mechanical and viscoelastic properties than other gradient patterns and non-graded samples, despite the same geometry and SG content.

Incorporation of SG into phenolic increased the thermal stability of the resin and had a stabilizing effect against the decomposition.

The addition of MWNTs /multi-walled carbon nanotubes /, especially well-dispersed and functionalized MWNTs, reduce the CTEs of the nanocomposites.

Cont…. The extent of CTE reduction depends on the particle rigidity and on

the dispersion of the clay platelets in the matrix and also on an efficient stress transfer to clay layers.

• It is believed that the retardation of chain segmental movement through incorporation of organically modified clays also leads to decrease in the CTE.

• The interactions between nanotubes and polymer matrix appear to involve non–covalent bonding. With the moderate interaction and adequate dispersion of nanotubes, increases in Young’s modulus, tensile strength, and decomposition temperature.

• This non–covalent interaction between CNTs and matrix allows stress transfer from matrix to nanotubes, thereby increasing Young’s modulus.

SourcesArticle-1:Fabrication and characterization of functionally graded synthetic graphite/phenolic Nano composites:-• Centre for Material and Fibre Innovation, Deakin University, Locked Bag 20000, Geelong, Victoria 3220, Australia.• Department of Materials Engineering, Monash University, Clayton, Victoria 3800, Australia.• School of Engineering, Deakin University, Locked Bag 20000, Geelong, Victoria 3220, Australia. Article-2:Characterization of Nanocomposites by Thermal Analysis• Carola Esposito Corcione * and Mariaenrica Frigione• Department of Engineering for Innovation, University of Salento, Lecce 73100, Italy;• E-Mail: mariaenrica.frigione@unisalento.it• * Author to whom correspondence should be addressed; E-Mail: carola.corcione@unisalento.it;• Tel.: +39-0832-297-326; Fax: +39-0832-297-326.• Received: 10 September 2012; in revised form: 3 December 2012 / Accepted: 10 December 2012 /• Published: 19 December 2012 Article -3: Influence of Carbon Nanotube–Polymeric Compatibilizer Masterbatches onMorphological, Thermal, Mechanical, and Tribological Properties of Polyethylene• Maija Pöllänen, Sami Pirinen, Mika Suvanto, and Tuula T. Pakkanen*• Department of Chemistry, University of Eastern Finland, P.O. Box 111, 80101 Joensuu,Finland• *Corresponding author. Tel.: +358 132513340; fax: +358132513390• E–mail address: Tuula.Pakkanen@uef.fi (T.T. Pakkanen).

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