Nanoclays nanoclay-reinforced nanocomposites

An extensive survey of literature indicates that there was much less work done in the area of natural fiber reinforced nanocomposites. Hence, the work that is presently done can also be used as a reference in substituting the glass fiber with nanoclays and evaluating the performance characteristics. 

TPV nanocomposites of LLDPE/reclaimed rubber with nanoclay and 1 wt.% MA-grafted PE and curative were prepared using a Brabender internal mixer at 170°C (Razmjooei et al., 2012). Contents of the reclaimed rubber, nanoclay, and compatibilizer were varied up to 30, 7, and 21 wt.%, respectively. The blends without the compatibilizer were also prepared. Morphological, thermal, and mechanical properties of the nanoclay-reinforced TPV nanocomposites indicated intercalation and partial exfoliation by the high-shear stress during mixing with the reclaimed rubber. Vulcanization of rubber phase led to an increase of viscosity. The size of rubber particles in TPV was reduced with the addition of nanoclay and compatibilizer. 

Peltola, R, Walipakka, E., Vuorinen, J., Syrjiila, S., and Hanhi, K. 2006. Effect of rotation speed of twin screw extruder on the microstructure and rheological and mechanical properties of nanoclay-reinforces polypropylene nanocomposites. 

Nanofillers may be nanoclays, carbon nanotubes (single or multiwall) (CNTs), silica, layered double hydroxides (LDHs), metal oxides, etc., offering the promise of a variety of new composites, adhesives, coatings, and sealant materials with specific properties [32-37]. Among the fillers mentioned, nanoclays have attracted most of the academia and industry interest, due to their abrmdance as raw materials and to the fact that their dispersion in polymer matrices has been studied for decades [38]. In fact, there are three major polymer nanocomposites categories in terms of nanofiller type that are expected to compile the global nanocomposites market in 2011 nanoclay-reinforced (24%), metal oxide-reinforced (19%), and CNTs-reinforced (15%) ones [39-41]. 

A study on the nanocomposite is important since it can affect the structural characteristics of a composite when it is used as a matrix of the laminates or the reinforcement of a foam core. It has been reported that the characteristics of the composite structure can be improved when a nanoclay-reinforced epoxy is used as a matrix of laminates Antonio et al. [71] improved the damping coefficient and the energy dissipation characteristics of a glass-epoxy composite using nanoclay particles. Hosur et al. [72] improved the impact characteristic of a composite sandwich structure using the nanoclay infused foam. 

Hazarika A, Maji TK (2014c) Strain sensing behavior and dynamic mechanical properties of carbon nanotubes/nanoclay reinforced wood polymCT nanocomposite. Chem Eng J 247 33-41 Hazarika A, Maji TK (2014d) Thermal decomposition kinetics, flammability, and mechanical property smdy of wood polymtar nanocomposite. J Therm Anal Calorim 115 1679-1691 Hazarika A, Mandal M, Maji TK (2014) Dynamic mechanical analysis, biodegradability and thermal stability of wood polymer nanocomposites. Compos Part B 60 568-576 Hetzer M, Kee D (2008) Wootl/polymer/nanoclay composites, environmentally friendly sustainable technology a review. Chem Eng Res Des 86 1083-1093 Hill CAS, Abdirl KHPS, Hale MD (1998) A study of the potential of acetylation to improve the properties of plant fibres, frrd Crops Prod 8 53-63 Hoffmann MR, Martin ST, Choi WY, Bahnemann W (1995) Environmental application of semiconductm photocatalysis. Chem Rev 95 69-96 Huda MS, Drzal LT, Misra M, Mohanty AK (2(K)6) Wood-fiber-reinforced poly(lactic acid) composites evaluation of the physicomechanical and morphological properties. J AppI Polym Sci 102 4856-4869... 

Dai G, Mishnaevsky Jr L (2013) Damage evolution in nanoclay-reinforced polymers a three-dimensional computational smdy. Compos Sci Technol 74 67—77 Durmus A, Woo M, Kas goz A, Macosko CW, Tsapatsis M (2007) htbnealated linear low density polyethylene (LLDPE)/clay nanocomposites prepared with oxidized polyethylene as a new type compatibilizer stmctural, mcehanieal and barrier properties. Eur Polym J 43 3737—3749 Pan J, Liu S, Chen G, Qi Z (2002) SEM study of polystyrene/clay nanocomposite. J Appl Polym Sci 83 66-69... 

Bionanocomposites of PHBV reinforced with hydroxyapatite nanoparticles have been studied and compared to nanoclays-reinforced PHBV [254-257]. Maiti and Yadav [254] prepared bionanocomposites based on PHBV reinforced with layered silicate and hydroxyapatite by melt extrusion. The nanostructure, as observed from WAXS and TEM, indicated intercalated hybrids for layered silicates and uniformly distributed hydroxyapatite nanoparticles which conferred improvement in thermal and mechanical properties as compared to the neat copolymer. The layered sihcate nanocomposites exhibited superior mechanical properties as compared to hydroxyapatite bionanocomposites. It was also found that the rate of biodegradation of the copolymer was enhanced dramatically with both nanoreinforcements, and the hydroxyapatite bionanocomposite showed the highest rate of biodegradation. 

The mass transport mechaiusm of gases permeating in a nanocomposite is similar to that in a semicrystalline polymer. The nanocomposite is considered to consist of a permeable phase where non-permeable nanoplatelets are dispersed. There are mainly three factors that influence the permeabiUty of nanocomposites the volume fraction of the nanoparticles, their relative orientation to the diffusion direction and their aspect ratio. The gas transport behavior of two different nanoclay-reinforced EVA membranes has been analyzed using oxygen and nitrogen gases and the results were compared with neat EVA. EVA nanostructured polymer blends exhibit excellent barrier properties. 

Joshi et al. reported that nanoclay reinforced PP nanocomposites could be spun and drawn successfully for 0.5,1.0 and 1.5 wt% of the modified clay loading. Beyond 1.5 wt% the spirmability is poor." The modified clay content in the range of 0.5-1.0 wt% gives optimum properties." ... 

Nanocomposites General Motors and Basell Polyolefins continue the development of nanocomposites for high-volume applications in external trim parts such as body panels. Three grades of TPO-based nanocomposites reinforced with 2.5% nanoclay have been commercialized by Basell Polyolefins. The first application of these nanocomposites was a low-volume minivan step option. 

The fire-retardant mechanism associated with nanoclays has recently been studied and is likely to involve the formation of a ceramic skin which catalyzes char formation by thermal dehydrogenation of the host polymer to produce a conjugated polyene structure. " The nanocomposite structure present in the resulting char appears to enhance the performance of the char through reinforcement of the char layer. These effects would explain the apparent fire-retardant synergy observed when nanoclays are incorporated into polymer formulations containing condensed phase fire-retardant systems, including coated fillers. 

Fibers have been widely used in polymeric composites to improve mechanical properties. Cellulose is the major substance obtained from vegetable fibers, and applications for cellulose fiber-reinforced polymers have again come to the forefront with the focus on renewable raw materials. Hydrophilic cellulose fibers are very compatible with most natural polymers. The reinforcement of starch with ceUulose fibers is a perfect example of a polymer from renewable recourses (PFRR). The reinforcement of polymers using rigid fillers is another common method in the production and processing of polymeric composites. The interest in new nanoscale fillers has rapidly grown in the last two decades, since it was discovered that a nanostructure could be built from a polymer and layered nanoclay. This new nanocomposite showed dramatic improvement in mechanical properties with low filler content. Various starch-based nano-composites have been developed. 

---