Most commercial plastics encountered by consumers consist of building blocks of carbon. Those building blocks are typically derived from petroleum or natural gas, but can be derived from coal or biological sources. The building blocks of small molecules are called monomers. The monomers used are many and can be combined in various combinations to achieve special properties and characteristics.
The nature of the polymer science is such that the monomers must be very pure to make useful plastics. Plastics can be made at very high pressures using gases, in solvents or liquid emulsions, or as melted materials. Each plastic has preferred manufacturing techniques based on its specific chemistry. All successful chemical syntheses are characterized by purification of raw materials, reuse of surplus material, efficient conversion of materials to useful plastic, efficient use of energy, and minimized releases of byproducts to the environment.   _{Your Comment}