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Wollastonite has a huge potential to be utilized as a functional filler in the thermoplastic composites, providing an enhancement to the mechanical strength, as well as thermal stability and flame retardancy, thus replacing the other conventional fillers such as glass fibre and talc. Due to the reinforcing ability and good thermal stability of wollastonite, the wollastonite-filled polymer composites have attracted the attention of academicians and industrialists. Many studies are reported on the effect of wollastonite incorporation into the polymers, in the aspect of mechanical, thermal, and flammability properties, meanwhile exploring the potential of wollastonite usage in the desired applications. This review article will be focusing on the thermal and flammability properties of wollastonite-filled thermoplastic composites. The popular thermoplastics used as the matrix are polypropylene, polylactic acid, and poly(ethylene terephthalate). Studies on flammability properties of wollastonite-filled thermoplastic composites are relatively less compared to thermal properties. Generally, the properties of the composites are influenced by the wollastonite dispersion, loading, size and shape of wollastonite, and its interfacial adhesion with the polymer matrix. Most of the previous studies focused on thermoplastic filled natural micro-sized wollastonite composites. Thus, the effect of nano-sized synthetic wollastonite as a functional filler in polymers is worth investigating. Further research on hybrid wollastonite/nanofillers is also interesting to develop high-performance materials to meet the requirements of society and industries.

The topic on bioplastics is of considerable interest with respect to environmental pollution caused by non-biodegradable plastics. Great efforts have been made in producing biomaterials with minimum negative impacts towards the environment. Bioplastics accounted 1% of the 335 million tonnes of plastic production in a year. The market and demand are continuously growing as the development of new biopolymers, applications and products are emerging. The objective of the review work reported in this chapter is to provide recent advances and challenges in the utilization of agricultural waste (agro-waste) or by-products in the production of bioplastics; namely polylactic acid, thermoplastics starch and chitosan bioplastic. Various agro waste that has potential to be used as bioplastics are bagasse, corn cob, cellulose, sago pith waste and chitin. The trend of agro-waste as the source for bioplastics production is rising due to the relatively lower cost and easily available. However, the utilization of agro-waste for development of bioplastics is still limited due to the unsystematic and low cost-effective waste management system, limited data on waste generation, and low production yield compared to food feedstock. It is believed that the prospect of agro-waste as feedstock for bioplastics will improve with the advancement in biotechnology and government intervention. Government, public, industrialists and researchers should synergize to realize the commercialization of agro waste-derived bioplastics.

Chitosan is a linear semi-crystalline polysaccharide prepared by purification and deacetylation of chitin, which shown as Fig. 21.1. Chitin or poly (β(1–4)-N-acetyl-D-glucosamine) is one of the most abundant polysaccharides from natural sources which can be found in the exoskeleton of crustaceans and insects and in the cell walls of most fungi and some algae (Ma et al. 2017; Muxika et al. 2017). To purify chitin from the shells of crustaceans, the shells are ground, processed with HCl to achieve demineralization and boiled in dilute NaOH to remove proteins (Puvvada et al. 2012; Arbia et al. 2012; Kumari et al. 2015). Deacetylation of chitin is achieved through alkaline treatment at more than 80 °C. The degree of deacetylation is dependent on the reaction condition. Treatment with 12.5 mol/L NaOH at 95 to 100 °C deacetylates chitin within 2 hours, yielding chitosan with a degree of deacetylation of 87 to 90% and an average MW of 160 to 1600 kDa (Puvvada et al. 2012).

Polymer nanocomposites with enhanced performances are becoming a trend in the current research field, overcoming the limitations of bulk polymer and meeting the demands of market and society in tribological applications. Polytetrafluoroethylene, poly(ether ether ketone) and ultrahigh molecular weight polyethylene are the most popular polymers in recent research on tribology. Current work comprehensively reviews recent advancements of polymer nanocomposites in tribology. The influence of different types of nanofiller, such as carbon-based nanofiller, silicon-based nanofiller, metal oxide nanofiller and hybrid nanofiller, on the tribological performance of thermoplastic and thermoset nanocomposites is discussed. Since the tribological properties of polymer nanocomposites are not intrinsic but are dependent on sliding conditions, direct comparison between different types of nanofiller or the same nanofiller of different morphologies and structures is not feasible. Friction and wear rate are normalized to indicate relative improvement by different fillers. Emphasis is given to the effect of nanofiller content and surface modification of nanofillers on friction, wear resistance, wear mechanism and transfer film formation of its nanocomposites. Limitations from the previous works are addressed and future research on tribology of polymer nanocomposites is proposed.