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Polymers. Polymers are now widely used in all aspects of modern life. They contribute, to a great extent, to the comfort and improvement of the quality of life.

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Introduction

POLYMERS (Production & Disposal) Polymers are synthetic and natural macromolecules composed of smaller units called monomers. Many synthetic polymers are produced and utilized because they are resistant to chemical and physical degradation. These polymers resistant to degradation present disposal problems when their usefulness ceases. Polymers are now widely used in all aspects of modern life. They contribute, to a great extent, to the comfort and improvement of the quality of life. Their importance is based on their unique ultimate properties and flexibility for wide range of applications from simple packaging to heavy construction. Because of their low cost, they have been extensively used for disposable or throwaway packaging and containers. It is expected that, during the first few years of the 21st century, there will be a 2 to 3 fold increase in plastic consumption in developing countries, due to the rise in materials utilization as a result of increased rate of industrial growth. However, this is also accompanied by a vast accumulation of solid waste and plastic litter which, due to their resistance to biodegradation, have a deleterious effect on the environment as an obvious contributor to pollution. ...read more.

Middle

Another example is a polyester known as PET (poly(ethyleneterepthalate)), commonly found in drinks bottles, which forms a reaction form 2 monomers: ethylene glycol and terephthoyl chloride. At the reaction's end, an atom of hydrogen and an atom of chlorine are left out of each PET molecule, resulting in a bi-product of hydrogen chloride (HCl) gas. Peptides and proteins are also formed by condensation polymerisation. A peptide link (also known as an amide link) is formed between the amino and carboxylic acid groups in amino acids, with the loss of a water molecule. Hence both polyamides and proteins and proteins contain monomer units joined by the same link. The techniques used for shaping and finishing plastics depend on three factors: time, temperature, and flow (also known as deformation). Many of the processes are cyclic in nature, although some fall into the categories of continuous or semicontinuous operation. One of the most widely used operations is that of extrusion. An extruder is a device that pumps a plastic through a desired die or shape. Extrusion products, such as pipes, have a regularly shaped cross section. ...read more.

Conclusion

Most synthetic plastics are not environmentally degradable; unlike wood, paper, natural fibres, or even metal and glass, they do not rot or otherwise break down over time. (Some degradable plastics have been developed, but none has proved compatible with the conditions required for most waste landfills.) Thus, there is an environmental problem associated with the disposal of plastics. Recycling has emerged as the most practical method to deal with this problem, especially with products such as the polyethene terephlalate bottles used for carbonated drinks, where the process of recycling is fairly straightforward. More complex solutions are being developed for handling the commingled plastic scrap that constitutes a highly visible, albeit relatively small, part of the problem of solid waste disposal. Natural polymers or synthetic polymers based on naturally occurring monomers look to be the best bet for future development. However, some work must be done before these polymers can take the place of the synthetic polymers now in use. The natural or natural-mimicking polymers now known often lack some of the properties that make current synthetic polymers so popular, such as water resistance and other physical properties in addition to the relatively low cost of synthetic polymer production. Shahida Jaffer Page 1 of 3 ...read more.

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