Although only a chain of 3 are shown, polymers usually contain much longer chains. This form is most commonly known as Styrofoam TM . There are two basic types of polymers and they are amorphous and crystalline . Noncrystalline or amorphous polymers are soft solids such as rubber. Crystalline polymers take on very rigid forms such as the Plexiglas in the previous example.
Crystalline polymers are probably the more common of the two due to their physical properties.
The first commercial crystalline polymer was developed by Dupont and it is called Kevlar TM . Kevlar TM is used in bullet proof vests, helmets, and lightweight boat material. Allied-Signal Company has developed a more flexible crystalline polymer called Specta TM which is based on polyethylene. Spectra TM can be drawn into thin fibers and made into surgical gloves that resist cuts from scapels, but are also very fitting. Perhaps the most common example of cross linking is epoxy glue.