Biodegradable soft plastics

Polyesters are known to be produced by many bacteria as intracellular reserve materials for use as a food source during periods of environmental stress. They have received a great deal of attention since the 1970s because they are biodegradable, can be processed as plastic materials, are produced from renewable resources, and can be produced by many bacteria in a range of compositions. The thermoplastic polymers have properties that vary from soft elastomers to rigid brittie plastics in accordance with the stmcture of the pendent side-chain of the polyester. The general stmcture of this class of compounds is shown by (3), where R = CH3, n = >100, and m = 0-8. 

Depending on the particular structure, PHAs can be nearly amorphous or can be up to about 70% crystalline, and can range from soft and elastic to stiff and brittle. Metabolix PHAs are reported to be better water vapor barriers than most biodegradable plastics. WVTRs for 50 micron PHA film at 23°C and 90% RH range from 20-150 g/m2 d. 

Keywords Automotive interiors. Biodegradable plastics, Condoms, Designing structural components. Door handles. Fiber composites. Interior paneling elements. Joint endoprostheses. Kneading clay. Mats for office chairs (carpet protection). Packaging material. Parts in cars. Polycarbonate glasses, Pressboard, Rubber plates. Tires, Toys made of soft PVC, Utilization phase... 

A wide variety of general purpose cleansers is available with abrasive materials to facilitate the cleansing process. Conventional cleansers are petroleum-based and use pumice, sand, metal meshes, foams, rigid and textured plastics, and various composites as abrasive materials. Although these materials are effective, they are often too harsh for use in sensitive or soft areas. Further, many of the abrasives and their associated adhesives are not biodegradable so they remain in the plumbing and in the water system long after their use (2). 

The tendency for PLA plasticized with PEG to lose properties with time at ambient temperature is a major obstacle to its application as a biodegradable packaging material. Without plasticizer, PLA is stiff and brittle. Blending with low molecular weight PEG improves elongation at break and softness. The desired mechanical properties are achieved in quenched PLA/PEG blends with 30 wt% PEG However, the blends are not stable at ambient temperature and the attractive mechanical properties are lost over time. Crystallization and phase separation are possible aging processes. 

The polymeric/ soft materials chapter represents the largest expansion for the 2nd edition. This chapter describes all polymeric classes including dendritic polymers, as well as important additives such as plasticizers and flame-retardants, and emerging applications such as molecular magnets and self-repairing polymers. This edition now features click chemistry polymerization, silicones, conductive polymers and biomaterials apphcations such as biodegradable polymers, biomedical devices, dmg delivery, and contact lenses. 

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