Plastic
Thermoplastic
Most plastics we use in everyday life are thermoplastics. The more you heat plastic the more malleable (= plastic) it gets, which is its main characteristic. However, it melts in excessive heat, like a plastic bowl on a hot stove plate. This behavior distinguishes them from thermosets, which do not melt but decompose when heated.
Polyethene (also polyethylene, PE) and polyvinyl chloride (PVC) are the most commonly used industrially manufactured plastics. Everyday objects, like plastic or freezer bags, buckets, laundry baskets, crates or rubbish containers etc. are normally made of polyethen, but also pipes or wire insulation are often made of this material. At room temperature PE is a rather soft thermoplastic. You can easily scratch an object made of PE with your finger. However, the material behaves very stable towards chemicals: salt solutions, alkalis and most inorganic acids dont’t attack the material and even nail polish remover is sold in polyethene bottles. Without added pigments polyethene is translucent but not completely transparent, unless the material is processed into a very thin film. Depending on the manufacturing process the density of polyethene is between 0.90 and 0,95 g/cm3that is it floats in water.
Polystyrene (PS) is a widely used thermoplastic mass plastic. It is produced by radical polymerization of styrene. In the chemical industry this substance is a liquid that is manufactured from petroleum. Pure PS is hard, colorless and brittle. The high gloss surface is striking. Polystyrene is acid-, alkali-, and alcohol-resistant. However, it is attacked by many non-polar solvents.
Polypropene (also polypropylene, PP) is a relatively young plastic. In 1954 it was synthesized and industrially produced for the first time by scientist Giulio Natta in Italy. The synthesis is based on the Ziegler-Natta polymerization.
Polyvinyl chloride (PVC) is used in many different areas in large quantities. By adding different substances the elasticity of polyvinyl chloride can vary widely and that’s why it is both used as a hard material for pipes, gutters or shell suitcases and as a soft material for garden hoses and floor covering. Even the good old vinyl record is – as the name implies – made of PVC. This plastic is even processed as PVC paste to be applied on textiles (for rain coats) or on foamed material (for upholstered furniture).
