A Plastic material is of Synthetic or Semi-synthetic Organic Solids’. Some of them are moldable and others non-moldable. Plastics are typically cross chains of hydrocarbons but often contain other substances. They are usually synthetic, most commonly derived from Petrochemicals, but many are partially natural.
Most plastics contain other organic or inorganic compounds blended in. The amount of additives ranges from zero percentage for polymers used to wrap foods to more than 50% for certain electronic applications. The average content of additives is 20% by weight of the polymer.
Plastics are usually classified by their Chemical Structure of the polymer's backbone and side chains. Some important groups in these classifications are the Acrylics, Polyesters, Silicones, Polyurethanes and Halogenated plastics. Plastics can also be classified by the chemical process used in their synthesis, such as Condensation, Polyaddition and Cross-linking.
There are two types of plastics: Thermoplastics and Thermosetting Polymers. Thermoplastics are the plastics that do not undergo chemical change in their composition when heated and can be molded again and again. Examples include Polyethylene, Polypropylene, Polystyrene, Polyvinyl Chloride, Nylon, Rubber and Synthetic Rubber.
Thermosets can melt and take shape once; after they have solidified, they stay solid. In the thermosetting process, a chemical reaction occurs that is irreversible. The vulcanization of rubber is a thermosetting process.
Biodegradable plastics break down (degrade) upon exposure to sunlight, water or dampness, bacteria, enzymes, wind abrasion, and in some instances pest, or insect attack. Some modes of degradation require that the plastic be exposed at the surface, whereas other modes will only be effective if certain conditions exist in landfill or composting systems.
Due to their relatively low cost, ease of manufacture, versatility, and resistant to water, plastics are used in an enormous and expanding range of products, from paper clips to spaceships. They have already displaced many traditional materials, such as Wood, Stone, Leather, Paper, Metal, Glass etc.