Degradable polymers, natural

Color in water (apart from textile dyes, etc.) often is caused by the degradation of natural organic matter, resulting in colloidal humic and fiilvic acids. These are best removed by precipitation with metal salts, but performance may be improved with high-charge cationic polymers. 

Several review articles are available on the synthesis, physico-chemical properties, and bio degradability of natural-based polymers, and their composites [6-9]. The same aspects have been the subjects of recent books [10-12]. In the following account, we concentrate on organic esters of cellulose. 

The consequence of this inappropriate materials selection is the squandering of natural resources that characterises the industrialised nations of the world, coupled with a growing problem of waste disposal. Control is certainly necessary to prevent the uncontrolled dumping of these non-degradable polymers in the environment. Arguably control is also needed to prevent these kinds of material being fabricated into barely serviceable items in the first place. 

As described previously, ester bonds and polyesters are used extensively in nature for temporary storage of carbon. The relative ease of making and breaking ester bonds makes them an ideal choice for degradable polymer backbones. 

Copolyesters (such as BIOMAX ) which combine aromatic esters with aliphatic esters or other polymer units (e.g. ethers and amides) provide the opportunity to adjust and control the degradation rates. These added degrees of freedom on polymer composition provide the opportunity to rebalance the polymer to more specifically match application performance in physical properties, while still maintaining the ability to adjust the copolyesters to complement the degradation of natural products for the production of methane or humic substances. Since application performance requirements and application specific environmental factors and degradation expectations vary broadly, copolyesters are, and will continue to be, an important class of degradable polyesters. 

PVA films buried in soil were tested after 120 days and showed only very limited signs of biodegradation, and even field tests with PVA sheets buried for 2 years in different natural soil sites showed only limited (10%) weight loss. No traces of colonising microorganisms were detected on the incubated material. Degradable polymers like poly(hydroxy butyrate), PCL or starch are usually extensively... 

Solid waste discharges from chemical plants can represent very large problems, especially from paper mills, plastics plants, and food processing plants. Some materials do not decompose in the environment, and can become burdens when they accumulate. Some polymers have backbones that degrade in nature, such as aliphatic polyesters and polyvinyl alcohols others do not, such as polyethylene and polystyrene. 

In the future, new degradable polymers should be able to participate in the metabolism of nature. In the last chapter we give some examples of novel polymers with inherent environmentally favorable properties such as renewability and degradability and a series of interesting monomers found in the metabolisms and... 

Natural rubber oligomers with (i-pinene terminal units have been synthesized by Gutierrez and Tlenkopatchev via metathesis depolymerization [151]. The bulk degradation of natural rubber in the presence of (i-pinene, as chain-transfer agent, and C4 (0.1 mol% related to polymers with Mn between 490 and 1,700 kDa) produced monoterpene-terminated oligomers in yields between 80% and 90%. The results were further confirmed with model CM reactions using (i-pinene and (Z)-3-methyl-2-pentene. 

Wood and, polymers. Natural materials as well as materials manufactured from plant or animal origin, such as wood, cotton, paper products, wool, and leather, etc., are fully biodegradable under aerobic conditions. (Dexter)5 Plastics are materials that consist mainly of highly polymeric, organic compounds. Also, nondegradable polymer may become degradable by a combined chemical, physical, and biological attack.64,67... 

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