Plastics Characteristics
Plastics are made from fossil fuels--petroleum,
natural gas, coal--, wood and some plant materials, air,
water and sometimes other common materials. They are
designed in many different formulas for different
purposes. There are two main types:
Thermoplastics soften when heated, harden when
cooled, so caution is required in use. Examples are:
Acrylic, Cellulosic, Nylon, Polyethylene, Polystyrene,
Polypropylene, and Vinyl.
Thermosetting plastics are set into permanent shape
with heat. They do not soften when reheated. Examples
are: Phenolic, Melamine, Urea and Thermoset Polyester.
Properties of basic plastics resins can be changed by
adding fillers, plasticizers, or stabilizers. Examples
are: Polystyrene, which cracks easily, can be made to
resist impact by addition of rubber modifiers; Polyester
resin, reinforced with glass fibers, makes durable
products such as shower stalls or boats.
Plastics may be shaped by molding, casting extrusion,
calendaring, and foaming. Examples are as follows:
Molded-dishes, furniture
Cast-furniture, cutlery handles
Laminated-materials for counter tops, furniture
Extruded-fibers
Calendared-plastic film, plastic-coated fabric
Foamed-upholstery foam, sponges