Biodegradable Plastic

摘要

There has been tremendous research going on throughout the world on biodegradable plastics. Biodegradable plastic materials are broadly classified into two main class namely, biodegradable polymers and biopolymers. Biodegradable polymers are the synthetic oil-based polymers that have inherent constituents like poly caprolactone, poly hydroxybutyrate and poly (vinyl alcohol) to ease degradation or are chemically modified to assist biodegradation and are eco-friendly. Biopolymers are naturally occurring polymers such as cellulose, polysaccharides and proteins or derived from these natural polymers. Unlike synthetic polymers these biopolymers are biodegradable moieties and hence they can be decomposed by fungal or bacterial activity into natural metabolites. These biodegradable plastics have a vast application as carriage, packaging material. Most commercially available biodegradable plastic packaging materials are based on natural materials e.g. polysaccharides (cellulose, starch). This is because starch is a renewable, abundant and inexpensive resource. When used alone in packaging applications, starch exhibits a poor performance because of its brittleness and hydrophilic nature. To overcome such problems, starch is often modified mechanically, physically or chemically by combining with a plasticizer or polymeric additives. Where starch is blended with biodegradable polymers or copolymers, the concentration of starch in the mixture is used to classify, label or demarcate the material. The design of biodegradable polymers must ensure its functionality during use, as it may get destructed in response to an environmental effects such as temperature, light, hydration or microbial effect its use. Alternatively, degradation may be triggered by additives that catalyze the breakdown of the polymer chains under specific environmental conditions. Polymers must remain stable during manufacture and use but, they may undergo breakdown rapidly when discarded into landfills. Degradation can be monitored using physical changes or chemical changes, for example, by the observation of new functional groups in Fourier Transform Infrared Spectroscopy (FTIR) spectra. The routine approach to detect degradation is to measure weight loss.