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 Wysłany: Nie 0:40, 08 Maj 2011 Temat postu: christian louboutin sko Sustainable development, e |
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Environmental materials technology for sustainable development
Research. Biodegradable plastic polymer materials can be divided into three categories: (1) microbial polyester (polymer chains containing ester compounds); (2) from plants of the natural polymer (starch, cellulose, etc.) ; (3) chemical synthesis of polymers. These molecules may be the mechanism of degradation has been confirmed: the main by bacteria or their enzymes to high molecular weight molecules into smaller molecular weight fragments, and then further decomposed by bacteria into carbon dioxide and water and other substances. Microbial fermentation is a type of polyester macromolecules, it is the enzymes produced by microorganisms in nature easily biodegradable polyester material depolymerization hydrolysis, decomposition of absorption of synthetic polymers, these compounds and microbial polysaccharides with microbial polyesters and so on. To reduce the cost of manufacturing bio-polyester, the ongoing use of plant synthesis of biodegradable plastics. United States, Japan has used genetic engineering techniques, so that some of its branches and leaves of plants grown directly on biodegradable polyester,[link widoczny dla zalogowanych], such as the Michigan State University research team to microbial polyester biosynthesis genes into plants in the system, has successfully developed a polyester can be synthesized. Starch manufacturing plant, the price at 2.5 yuan / kg, is a kind of low prices and huge number of natural macromolecules, at home and abroad to carry out this kind of starch synthesis of biodegradable plastics is very hot. U.S. pharmaceutical companies Havana Lan Bate through the operation of plant genes, and partial control of macromolecular chains of starch branching degree, thus creating the cheap starch as raw material of biodegradable plastics. The company has been promoting the application of medicinal starch capsule, and success. On this basis, they also use the starch and a mixture of biodegradable polymer developed a thermoplastic biodegradable plastics, and to mixture of denatured alcohol and developed a name. Mater-Bi biodegradable plastics, and the annual production of 10,000 tons or more. The author is also wide in recent years, research and development of starch plastics I, has made it difficult thermoplastic of the starch can be used ordinary plastic molding processing equipment, but with similar products developed abroad, there is the problem of poor water resistance. Although, in recent years toward the use of domestic and international market also was marked with a biodegradable plastic packaging products , it should be noted that such is not the true meaning of degradable plastics can be recycled biological material, only as part of the degradation and semi-degradable materials. because the vast majority of degradable plastics is 30% to 40% starch and 60% 70% of the non-biodegradable synthetic resin blending a mixture of semi-biodegradable plastic-type I, the majority can not be biodegradable into water and carbon dioxide. of course there is a category known as light degradation of biodegradable plastic is plastic, such plastic substance Light is also not fully degradable plastics, which are contained by the plastic photodegradation initiator (photosensitizer), long-term exposure to sunlight encountered when a small amount of plastic contained in the light induced degradation agent. macromolecules into a medium molecular weight the. debris, and difficult to further break down into carbon dioxide and other natural substances can be recycled. The third category is the use of biodegradable plastics, biodegradable synthetic polyester macromolecules. We know that the majority of the synthetic polymer materials can not be species decomposed by microorganisms, but we know that some water-soluble macromolecules (such as polyvinyl alcohol and polyethylene glycol, etc.) and some aliphatic polyester (such as: polycaprolactone (PCL), polylactic acid,[link widoczny dla zalogowanych], etc.) can be decomposed by microorganisms. PCL and natural macromolecules with the same degree of good biodegradability and excellent physical properties, but relatively low melting point (about 60 ℃) and the price is still high, not as biodegradable plastics and practical. As can be bio-degradable plastics environmental microbial decomposition, thus dealing with household waste, use of biological metabolism,[link widoczny dla zalogowanych], to turn it into fertilizer (compost) can be used as a natural organic fertilizer. Not only that, in the water and high temperature conditions, can be polyester, etc. Hydrolysis of biodegradable plastics, and the higher recovery rate recovery of its monomer (synthetic polyester material), then the monomer purification and polymerization, the biodegradable polyester can be changed again (that is, for the molecular loop .) anticipation of the near future, environmental protection and efficient use of resources from the two sides to carry out bio-degradable plastics research and development, in order to lay the sustainable development of human essential materials technology base. as closely linked to human with biological materials can be recycled timber is a category one by one in harmony with the environment and a very large amount of useful material. timber is essentially a natural composite materials and composite structures. does not destroy the ecological balance in the circumstances,[link widoczny dla zalogowanych], reasonable the use of wood is to protect the ecological environment and sustainable development of the effective ways,[link widoczny dla zalogowanych], because the growth of timber
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