Introduction on polymers Essay Example | Topics and Well Written Essays - 1500 words

Introduction on polymers - Essay Example Thermosetting polymers the chains become cross-linked so that the solid materials are produced that can not be softened and that ca not flow. Polymers are usually made in one of two polymerization process. In condensation-polymerization the linking of molecules creates a by product, which is usually water nitrogen or hydrogen gas. Thermoplastic polymers consist of a series of long-chain polymerized molecules in which all the chains are separate and can slide over one another. Thermoplastic polymers The long chains of thermoplastic polymer are connected by weak forces alongside the chemical bonds extremely strong. When they are heated the walls weaken and the polymer becomes soft and flexible at a high temperature and becomes a viscous melt. The cycle can be reversed by cooling of the materials. Thermoplastic elements usually can be of semi-crystalline structure or amorphous structure. Civil engineering materials such as polyester, nylon 66 and polycarbonate are the best examples of a morphous thermoplastic polymers. The developments polymers technology has led to high performing types of polymers such as polythersulphone which is amorphous in nature and polyetheretherketone which are semi crystal-line. The above two are more efficient than the normal thermoplastic, although they are not employed in civil engineering due to high costs. Thermosetting polymers They can be used in two separate ways firstly as a composite that is when combined with fibrous materials and secondly when as an adhesive and maybe as epoxies. They are formed in two stage chemical reaction when a polymer such as polyster, vinylester or epoxy is reacted with a curing agent. The reaction can be performed in a normal room temperature or the application of either controlled heat or pressure. Thermosetting polymers are strong in nature and can be affected by heat. The two procedures used to polymerize the thermosetting polymers used in civil engineering are the cold system that are cured at ambi ent temperatures and the hot cure system whereby polymerization is performed at elevated temperatures. Polymer science The research on polymer science continues to come up producing new products in the market. The polymer science and engineering are marching together although they are more interested on new materials being produced. Poly was scientifically born to understand how rubber and plastic works and they can not be separated. Polymers are now forming the basis of clothing and automobiles among others. New elastomeric, plastics, adhesives, coatings and fibers among others are being invented by the use of new technology in science. The scientific theory accepts the relationship between polymer structure, physical property and their behavior. Polymers are playing a very important role in processing of other industrial products. Anisotropy in thermoplastic polymers plays a significant role in thermal conductivity. Highly drawn semi-crystalline polymer samples can have a much hig her thermal conductivity as a result of orientation of the polymer chains in the direction of draw. For amorphous polymers, the increase in thermal conductivity in the direction of the draw is usually not higher than two. Many polymers experiment a viscous reaction as an elastic response towards stress and strain. Combinations of some elastic and various viscous elements are being used to determine the melting behavior of polymers. The above characteristics make them be classified under the