In this issue, we continue our understanding of plastics from a chemical perspective.
Properties of plastics: The properties of plastics depend on the chemical composition of the subunits, how those subunits are arranged, and how they are processed. All plastics are polymers, but not all polymers are plastics. Plastic polymers are composed of chains of linked subunits called monomers. If the same monomers are linked, a homopolymer is formed. Different monomers are linked to form copolymers. Homopolymers and copolymers can be linear or branched. Other properties of plastics include: Plastics are generally solid. They can be amorphous solids, crystalline solids or semi-crystalline solids (microcrystals). Plastics are generally poor conductors of heat and electricity. Most are insulators with high dielectric strength. Glassy polymers tend to be hard (eg, polystyrene). However, flakes of these polymers can be used as films (eg polyethylene). Almost all plastics show elongation when stressed and do not recover when the stress is relieved. This is called “creep”. Plastics tend to be durable and degrade very slowly.
Other facts about plastics: The first fully synthetic plastic was BAKELITE, manufactured by LEO BAEKELAND in 1907. He also coined the word “plastic”. The word “plastic” comes from the Greek word PLASTIKOS, which means it can be shaped or moulded. About one-third of the plastic produced is used to make packaging. The other third is used for siding and plumbing. Pure plastic is generally insoluble in water and non-toxic. However, many additives in plastics are toxic and can leach into the environment. Examples of toxic additives include phthalates. Non-toxic polymers can also degrade into chemicals when heated.
After reading this, have you deepened your understanding of plastics?
Post time: Sep-17-2022