Learn the basics about thermosetting and thermosoftening polymers, when learning about polymers as a part of organic chemistry.

A polymer is a macromolecule made of many monomers, or repeating units.

The properties of these polymers depend on a variety of factors – the monomer unit, the linkages between each monomer that link the monomers together, and the intermolecular and intramolecular forces that exist between polymers.

In this video, we will learn about two classes of polymers – thermosoftening polymers and thermosetting polymers.

The term “plastics” is used to describe a wide range of polymers made of monomers derived from the products obtained from the fractional distillation of crude oil.

Polyethene, polypropene, and polyvinyl chloride are thermosoftening polymers. This means that they soften when heated – when soft and in liquid form, they can be moulded into many different shapes.

These plastics are used to make many everyday items, such as window and door frames, pipes, wiring insulation, and waterproof clothing items, to name just a few. This is made possible because the polymers are not linked together. The polymers can slide over one another, making items made from them soft and flexible.

These polymers interact only by weak intermolecular forces, and can therefore be separated rather easily when heated, giving them relatively low melting points.

Other thermosoftening polymers include polystyrene and polytetrafluoroethylene.

Thermosetting polymers, on the other hand, do not soften when heated. Thermosetting polymers are cross-linked to one another. The presence of cross-links hardens the overall structure. A good example of a thermosetting polymer is vulcanised rubber. Rubber tapped from Para rubber trees is a polymer of isoprene monomers. On its own, it is a runny white liquid that can be processed to make latex gloves, balloons, and erasers. It is also used to make bicycle and car tires, though it has to be vulcanised first.

In the vulcanisation process, sulfur is added so disulfide bridges link the polymers together.

The presence of these cross-linkages greatly increases its strength and therefore it does not soften easily when heated.

Other examples of thermosetting polymers include Bakelite used to make old TV sets, and certain types of strong glue.

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