High Trans Polybutadiene Polybutadiene BR

23 concentration of 1,4 trans units has a strong influence on the strain induced crystallization of the rubber, which means a reinforcing effect on the tensile ultimate properties: in this sense, natural rubber shows a strain induced crystallization behavior. Moreover, the relative concentration of 1,4 and 1,2 units may influence the thermal stability of the polymer. The oxidative degradation of the rubber starts from the addition of oxygen on a double bond: if the double bond id part of the main chain, as in the case of 1,4 units, the reaction will lead to a chain scission. 2.9 Polymer Nowadays, the polymer industry has grown to be larger than the metals industries, as polymers have already had a range of applications in nowadays industry. These included adhesive, coatings, foams and even to packaging materials to textile and industrial fibers industry. Polymer is a large molecule macromolecule composed of repeating structural units typically connected by covalent chemical bonds. Plastic is the most synonyms with this term and this term actually refers to a large class of natural and synthetic materials with a variety of properties. Polymers have become an essential and ubiquitous role in everyday life due to the extraordinary range of properties accessible in polymeric materials, from plastics and elastomers on the one hand to natural biopolymers such as DNA and proteins that are essential for life on the other. A simple example is polyethylene, whose repeating unit is based on ethylene IUPAC name ethene monomer. Most commonly, as in this example, the continuously linked backbone of a polymer used for the preparation of plastics consists mainly of carbon atoms. However, other structures do exist; for example, elements such as silicon form familiar materials such as silicones, examples being silly putty and waterproof plumbing sealant. The backbone of DNA is in fact based on a phosphodiester bond, and repeating units of polysaccharides e.g. cellulose are joined together by glycosidic bonds via oxygen atoms. Natural polymeric materials such as shellac, amber, and natural rubber have been in use for centuries. The list of syntheticpolymers includes synthetic rubber, Bakelite, neoprene, nylon, PVC, 24 polystyrene, polyethylene, polypropylene, polyacrylonitrile, PVB,silicone, and many more.Wikipedia 2009

2.10 Epoxy

Epoxy or polyepoxide is a thermosetting polymer formed from reaction of an epoxide resin with polyamine hardener. Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives.

2.11 Chemistry of Epoxy

Epoxy is a copolymer; that is, it is formed from two different chemicals. These are referred to as the resin and the hardener. The resin consists of monomers or short chain polymers with an epoxide group at either end. Most common epoxy resins are produced from a reaction between epichlorohydrin and bisphenol-A, though the latter may be replaced by similar chemicals. The hardener consists of polyamine monomers, for example Triethylenetetramine TETA. When these compounds are mixed together, the amine groups react with the epoxide groups to form a covalent bond. Each NH group can react with an epoxide group, so that the resulting polymer is heavily crosslinked, and is thus rigid and strong. The process of polymerization is called curing, and can be controlled through temperature, choice of resin and hardener compounds, and the ratio of said compounds; the process can take minutes to hours. Some formulations benefit from heating during the cure period, whereas others simply require time, and ambient temperatures. Figure 2.8 : Structure of unmodified epoxy prepolymer resin