Polyesters production from renewable resources

The increasing amounts of plastic products from petrochemical-based polymers in a landfill have led to serious environmental concerns over the past decade. In recent years, various biodegradable plasties have been developed as a sustainable alternative to replace commodity synthetic plastics. Polylactic add is typical biodegradable polyester produced from renewable resources and a versatile polymer that has been used for many applications in the biomedical industry [1] as well as the packaging industry [2,3]. PLA has been blended with other biodegradable and synthetic polymers for the development of improved properties, such as poly (e-caprolactone)[4], poly (vinyl butyral)[5], poly(3-hydroxy butyrate)[6], poly (ethylene oxide)[7], and poly(p-vinyl phenol) [8]. 

Several synthetic procedures have been developed for the production of biodegradable polyester-based materials from 1,3-propanediol and succinic acid obtainable from renewable resources. 

Due to the rapidly increased production cost of fossil (petroleum)-based chemicals, fermentatively produced fumaric acid from renewable resources could replace current petrochemically based maleic acid as unsaturated dibasic acid mainly in the polyester resin industry but also in medicine and food industries in the nearby future. However, this can be achieved only if the bio-based production process for fumaric acid would be economically competitive with the current fossil-based process. This change requires the improvement of the large, past-operating fermentation processes for acid production in many aspects, such as production of free acid at a low pH, product yield and productivity, cheap and renewable raw material, and problems related to cell morphology and mass transfer. 

Aliphatic thermoplastic polyesters represent a class of materials that is attracting a considerable amount of attention because they are i) biodegradable and biocompatible and ii) increasingly accessible from the exploitation of diols and dicarboxylic acids derived from renewable resources. If long methylene chains are present in the monomers, the ensuing products resemble polyethylene (PE) in strnctnre and, hence, in most properties, have the added advantage of biodegradability. 

Biodegradable polymers can be mainly classified as agro-polymers (starch, protein, etc.) and biodegradable polyesters (polyhydroxyalkanoates, poly(lactic acid), etc.). These latter, also called biopolyesters, can be synthesized from fossil resources but main productions can be obtained from renewable resources (Bordes et al. 2009). However for certain applications, biopolyesters cannot be fully competitive with conventional thermoplastics since some of their properties are too weak. Therefore, to extend their applications, these biopolymers have been formulated and associated with nano-sized fillers, which could bring a large range of improved properties (stiffness, permeability, crystallinity, thermal stability). The resulting nano-biocomposites have been the subject of many recent publications. Bordes etal. (2009) analyzed this novel class of materials based on clays, which are nowadays the main nanoflllers used in nanocomposite systems. 

The main monomers for the most common biodegradable polyester production, which can now be obtained from renewable resources are succinic acid, 1,4-butanediol, 1,2-ethanediol, sebacic acid and azelaic acid. 

However, not many people realize that polyethylene, another product that Commoner was very worried about, was originally produced in Britain by the fermentation of grain to produce alcohol and dehydration of alcohol to produce ethylene. It and many other common plastics including styrene and polyester can be produced by known chemical processes from renewable resources such as wheat, cellulose, starch, biomass, etc. through the following chemical reactions. 

Eco-compatible Bioplastic Packaging in China based on Polyesters from Renewable Resources, aims at accelerating in China the production of PHAs obtained from renewable resources to develop foamed rice-bowls and kitchenware to alleviate the problem of white pollution in China and also in other Asian countries. 

Poly(lactic acid) (PLA) has gained tremendous attention in the past decade due to its desirable characteristics, namely, degradability under biotic or abiotic conditions, non-toxicity of polymer and degradation by-products, and adequate mechanical properties for use in select applications. Copolymerization of naturally occurring L-lactic acid with various polyester-forming monomers may potentially yield materials that display novel physical properties while maintaining reasonable degradation profiles. This approach also offers economical and environmental benefits due to the fact that L-lactic acid can be obtained from renewable resources, such as com. ... 

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