Buy essays on Biodegradable polymers and the environment

Biodegradable polymers were developed several decades ago, but their full-scale commercial application formed very slowly. Such situations had a place because they were generally more expensive and have less stable physical properties than conventional plastics. In addition, there was little incentive for producers of plastic products in order to include biodegradable materials in their products. However, situation greatly changed and now biodegradable polymers are in area of researchers’ interest, because they could be use in medicine, agriculture, packaging and many other areas.
ISO definition of the concept “biodegradable”
According to Narayan and Pettigrew (1999) we see that the American Society for Testing of Materials (ASTM) and the International Standards Organization (ISO) define degradable plastics as material that undergoes an essential change in its chemical structure under the influence of specific environmental conditions. It is necessary to add to this definition that exactly these essential changes result in a loss of not only physical, but also mechanical properties. Naturally occurring microorganism, which are presented by bacteria, algae and fungi greatly influence on biodegradable plastics and change its quality and structure. Gross and Bhanu (2002) stated that “plastics may also be designated as photodegradable, oxidatively degradable, hydrolytically degradable, or those which may be composted.” True definition of the term “biodegradable” was the object of great public interest between October 1990 and June 1992, when it was the main topic of debates and lawsuits. s
Structure and green chemistry of biodegradable polymers
Natural and synthetic polymers containing links, which are easily hydrolysed, possess a high potential for biodegradation. The presence of constituents in the polymer chain often promotes biological degradation. The last also depends on the degree of substitution and chain length of its sections between the functional groups, the flexibility of macromolecules.
An important factor, which determines the stability of the biodegradable polymer, is the value of its molecules. Simon, Muller, Koch and Muller (1998) proved that while microorganisms may affect monomers or oligomers and serve them a source of carbon, polymers with high molecular mass are resistant to the action of microorganisms. Biodegradation of most technical polymers typically initiate the process of non-biological nature (thermal and photo-oxidation, thermolysis, mechanical degradation, etc.). These degradation processes lead to lower molecular weight polymer. This gives rise to low molecular bio assimilated fragments having at the ends of the chain hydroxyl, carbonyl or carboxyl groups.
We see that polymers chains by the chemical hydrolysis may be broken down and results of such green chemistry presented in the figure 2. Gross and Kalra (2002) explained this process in the next way: “BPs are often derived from plant processing of atmospheric CO2. Biodegradation converts them to CO2, CH4, water, biomass, humic matter, and other natural substances. BPs are thus naturally recycled by biological processes.”