A polymer is a high molecular-weight material, either synthetic or natural, that is composed of repeating units called monomers. In some cases a natural polymer like rubber has been replaced on the market by a synthetic polymer that closely resembles, or even duplicates, the molecular structure of the natural model. The synthetic copies are usually altered to emphasize the desired properties. Types of synthetic polymers include plastics ( thermosets and thermoplastics), elastomers, fibers, coatings, and adhesives.

Thermoplastic materials can be formed and then remelted due to their long flexible carbon chains. Examples include ABS (acrylonitrile-butadienestyrene), cellulose acetate, nylon, polyethylene, polypropylene, polystyrene, PVC (polyvinyl chloride), and polyvinylidene chloride. These materials are also the most easily recyclable plastics.

Thermoset plastics are those polymers whose long carbon chains are bonded together like a rigid net. Well known thermoset plastics include allylic, epoxy, melamine and urea-formaldehyde, polyesters, polyurethane, and...