4.2d: Plastics

4.2d
Plastics
Most plastics are produced from petrochemicals. Motivated by the finiteness of oil reserves and threat of global warming, bio-plastics are being developed. these plastics degrade upon exposure to sunlight, water or dampness, bacteria, enzymes, wind erosion and in some cases pest or insect attack, but in most cases this does not lead to full breakdown of the plastic.

     History of Plastics

• Natural plastics - these are naturally occurring materials that can be said to be plastics because they can be easily shaped and moulded by heat.

Pine tree resin jewelry

Wax used for sealing letters

• Semi synthetic plastics - these are made from naturally occurring materials that have been modified or changed but mixing other materials with them. 
• Bakelite - was initially used in electrical goods; is cheap and easy to manufacture and gave a consistently high quality product.
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• Synthetic plastics - These are materials that are derived from breaking down, or 'cracking' carbon based materials, usually crude oil, coal, or gas, so that their molecular structure changes.

Synthetic plastic products

     Raw materials for plastics

Crude oil is used as a raw material for most plastic manufacture

• plastics derive from natural materials such as crude oil , coal and natural gas (crude oil being the most prominent raw material used. 

Synthetic plastic products

• all plastics are based on polymers and they are created by bonding molecules together. The terms monomer and polymer are very important in the plastics industry - a monomer is a relatively small molecule that can chemically bond to other monomers, forming a polymer.