Processing of polymer nanocomposites

Abstract Polymer nanocomposites processing requires incorporating nanoparticles into polymer matrix in a controllable fashion in order to successfully transfer the outstanding properties of nanoparticles to the final nanocomposite. This chapter first reviews various processing techniques to fabricate nanoparticles reinforced polymer nanocomposites. It then discusses some critical processing-related issues for property improvement, including the selection of nanoparticle and polymer matrix, quality of dispersion, ahgnment and functionahzation of nanoparticles. 

Key words polymer nanocomposites processing, carbon nanoparticles, 

Compositematerialcontainingatleastonephasewithconstituentsofl-lOOmn in size can be termed nanocomposites. Nanoparticles commonly used in the nanocomposite include single-walled carbon nanotube (SWCNT), double-walled carbon nanotube (DWCNT), multi-walled carbon nanotubes (MWCNT), carbon nanofiber (CNF), graphite nanoplatelet (GNP), mont-morillonite (MMT), nanoclay and polyhedral oligomeric silsesquioxanes (POSS). Other nanoparticles, such as SiOj, AljOj, TiOj and nanosilica are also used in the nanocomposite. The potential benefits of the nanoparticles for structural and multifunctional nanocomposites are sunamarized below. 

During the past few years, nanoparticles have been incorporated into the polymer matrix to develop a polymer nanocomposite. Although processing techniques of the nanocomposite are inherently different, all of them have to address the following issues that will directly affect the properties of the nanocomposite dispersion, alignment and functionalization. Common processing techniques of polymer nanocomposites include  

Solvent Boiling point (°C) Dielectric constant Density (g/mL) 

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Davis RD, Bur AJ, McBearty M et al. (2004) Dielectric spectroscopy during extrusion processing of polymer nanocomposites a high-throughput processing/characterization method to measure layered silicate content and exfoliation. Polymer 45 6487-6493... 

FIGURE 4.1 Schematic illustration of the synthetic process of polymer nanocomposites. (A) Direct mixing of the two... 

Capadona, J.R., van den Berg, O., Capadona, L.A., Schroeter, M., Rowan, S.J., Tyler, D.J., Weder, C. A versatile approach for the processing of polymer nanocomposites with self-assembled nanofibre templates. Nat. Nanotechnol. 2, 765-769 (2007)... 

In recent years, supercritical technology, especially supercritical carbon dioxide (scCCb), has been widely applied in the processing of polymer nanocomposites. A supercritical fluid is defined as "any substance, the temperature and pressure of which are higher than their critical values, and which has a density close to, or higher than, its critical density" (Darr Poliakoff, 1999). Fig. 3 shows a schematic representation of the density and organization of molecules of a pure fluid in solid state, gas state, liquid state and the supercritical domain. No phase separation occurs for any substance at pressures or temperatures above its critical values. In other words, the critical point represents the highest temperature and pressure at which gas and liquid can coexist in equilibrium. 

Wetzel, M.D. (2008) Environmental, health and safety issues and approaches for the processing of polymer nanocomposites. Proceedings of the 66lh SPE ANTEC, vol. 54, pp. 247-251. 

Processing of polymer nanocomposites 113 Table 4.2 Common methods of SWCNT sidewall functionalization... 

PROCESSING OF POLYMER NANOCOMPOSITES REINFORCED WITH POLYSACCHARIDE NANOCRYSTALS... 

The mechanical properties and reinforcing potential as well as the biodegradability of polysaccharides make them candidates for the processing of polymer nanocomposites (Dufresne 2010 Thakur 2013, 2015). 

Dufresne Alain. Processing of polymer nanocomposites reinforced with polysaccharide nanocrystals. Molecules. 15 no. 6 (2010) 4111-4128. 

Deepa B, Abraham E, Cherian BM, Bismark A, Blaker JJ, Pothan LA, Leao AL, de Souza SE, Kottaisamy M (2011) Structure, morphology and thermal characteristies of banana nano fibers obtained by steam explosion. Bioresour Technol 102(2) 1988-1997 Dufresne A (2010) Processing of Polymer Nanocomposites Reinforced with Polysaccharide Nanocrystals. Molecules 15 4111-4128... 

The organic modification of LDHs is an inevitable step in the process of polymer nanocomposites preparation. Therefore, the intercalated anions are important to the dispersion of LDHs and the resulting fire properties. Zammarano et al. [98] examined the effect of two organic modifiers, 3-aminobenzenesulfonic acid (ABS) and 4-toluenesulfonic acid monohydrate (TS), on the structure and properties of epoxy/LDH composites. Because of their reactivity with epoxy, ABS-modified LDHs (LDH-ABS) had better dispersion than LDH-TS. As a result, epoxy/LDH-ABS showed a greater reduction in PHRR (51%) than epoxy/LDH-TS at the same LDH loading. 

In conclusion, the development of the green process of polymer nanocomposite foams in order to achieve significantly optimized lightweight materials, that is, with good mechanical properties, high surface quality, and excellent thermal and highdimensional stability, stiU requires a lot of future work. 

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