A Look at the Many Types of Plastics

Plastic has become increasingly important in our every day lives. With so many different types of plastics, products meeting a broad range of consumer needs are available. For the most part, plastics are organic high polymers, which means they are made of large chainlike molecules that contain carbon. These polymers are changed into a plastic state either as they transition from a small-molecule chemical to a solid, or shortly after. Basically, large chainlike molecules are created by hooking together short-chain molecules. The precise process used to created this change, however, results in different types of plastics.

Thermoplastics Versus Thermosets

Plastic materials are divided into two basic groups: thermoplatics and thermosets. Thermoplastic materials are made of long molecules with side chains or with groups that are not attached to the other molecules. As a result, thermoplastics can be repeatedly melted and solidified through heating and cooling without a chemical change taking place. This means scraps created when processing thermoplastics can be reused. Thermoplastics are generally supplied to manufacturers in pellet form in order to be melted down and used.

Thermosets, however, cannot be reprocessed because they form crosslinked structures during processing. Scrap created when thermoset plastics are processed, therefore, must be discarded or used as a filler in other products. Thermoset plastics are supplied to manufacturers in liquid form or a solid molding powder that has been partially polymerized. They can be formed into their desired shape with or without pressure and heat or chemicals can be used to polymerize them.

Oddly enough, the line is not clearly drawn between thermoplastics and thermosets. In fact, some types of plastic are made as a combination of the two.