Thermoplastics can be reshaped because their linear or branched polymers can slide past one another when heat and pressure are applied. Adding Pigments imparts Color . Plastic products are commonly made from plastic powders. In compression molding, heat and pressure are applied directly to the powder in the mold cavity. The first important plastic, Celluloid, has been largely replaced by a wide variety of plastics known by such trade names as Plexiglas, Lucite, Polaroid, and Cellophane.
New uses continue to be found and include contact lenses, Machine gears, and artificial body parts.
The widespread use of plastics has led to environmental problems. Because plastic products do not decay, large amounts accumulate as waste. However, recycling is increasingly emerging as an alternative to disposal, particularly in communities with limited landfill capacity.