Thermoplastic polymers, life cycle

Recent researches in life cycle assessments (LCA) have also focused to enable PLA to find its place among traditional commodity polymers for many applications in the agricultural sector as well as in the packaging field (the food and nonfood sector). It was found that PLA can be processed like all other thermoplastic polymers with extrusion, injection molding, blow molding, thermoforming or fiber spinning processes into various products. 

Polymers reinforced with cellulose fibers have received much attention in recent years because of their low density, nonabrasive, combustible, nontoxic, low cost and biodegradable properties. Several authors have reviewed recent advances in the use of natural fibers in composites like flax [ 1 ], jute [2,3], straw [4], kenaf [5,6], coir [7-9], fique [10], among others. Natural fibers have been used to reinforce thermoplastics and thermosets polymers in automotive and aerospace applications [11]. The influence of surface treatments of natural fibers on interfadal characteristics was also studied [12-17], and Joshi et al. [18] compared the life-cycle environmental performance of natural fiber composites with glass fiber composites. In this study, natural fiber composites were found to be environmentally superior in most applications. 

Volume 1 of this book is comprised of 25 chapters, and discusses the different types of natural rubber based blends and IPNs. The first seven chapters discuss the general aspects of natural rubber blends like their miscibility, manufacturing methods, production and morphology development. The next ten chapters describe exclusively the properties of natural rubber blends with different polymers like thermoplastic, acrylic plastic, block or graft copolymers, etc. Chapter 18 deals entirely with clay reinforcement in natural rubber blends. Chapters 19 to 23 explain the major techniques used for characterizing various natural rubber based blends. The final two chapters give a brief explanation of life cycle analysis and the application of natural rubber based blends and IPNs. 

The production of durable functional products without using petroleum-based raw materials is a focus of much academic research today but it is also prioritized by many industries. Many questions still remain concerning the use, production and properties of bio-based and/or degradable polymers and whether or not they are more environmentally friendly than oil-based products. Polylactide is a bio-based compostable thermoplastic that is considered as one of the most promising materials for replacement of traditional volume plastics. The properties of polylactide can be tuned to resemble polystyrene, polyfethylene terephthalate) or polyolefins by controlling the stereochemistry by copolymerization or blending. This chapter reviews the life-cycle of polylactide based materials as well as the properties and applications. The recent trends in the area are also discussed. 

PP has lower specific gravity than other plastic materials. Having broad resistance to organic chemical ingredients, they are used in consumer products. The total environmental impact of PP and other thermoplastic materials is less than traditional materials in life-cycle analysis. Commercial PP is a complex mixture of varying amounts of isotactic, syndiotac-tic, and atatic polymers with a given MWD. 

Because of waste accumulation at the end of the life cycle of traditional polymer products, the development of environmentally-ffiendly, degradable, polymeric materials has attracted extensive interest. Nevertheless, the properties of such kinds of polymers are lower than that of traditional ones. Thermoplastic polymers have been widely used as matrix of composites reinforced with natural fibers in order to achieve a final material with improved mechanical properties with respect to the pure polymer. In order to obtain competitive products, the performance of biodegradable polymers can be greatly enhanced by the incorporation of nanometer-size fillers. 

Figure 2. Life cycle analysis results for energy content of various thermoplastic polymers. PLAl represents present technology PLA Bio/WP is the projection for the production of PLA from agricultural waste using wind power.

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