Polymers: Types, Properties and Classification

Polymers

A polymer is a very large macromolecule composed of many repeated smaller units known as monomers. Polymers have a typical organic structure. The properties of a polymer depend on the properties of the monomer from which it is obtained.

Classification of Polymers by Origin

• Natural: Found in nature in various forms and in living beings. Living cells contain proteins and starch, among others.
• Artificial: Obtained from natural polymers through chemical modification processes.
• Synthetic: Obtained as a result of manufacturing processes. Polyvinyl chloride (PVC) is an example widely used by humans.

Classification of Polymers by Physical Properties

• Elastomers: Have a high degree of elasticity, similar to rubber.
• Plastics: Have high strength and a degree of hardness. Deformation of a plastic is irreversible. The term plastic is incorrectly applied to all polymers.
• Thermosets: Are substances such as Bakelite, with great hardness and rigidity. They are not affected by heat.
• Thermoplastics: At high temperatures they pass to a liquid state and flow. When they cool, they harden again. Their molecular structure presents few or no cross-links.
• Thermostable polymers: Their function is not affected by heat. Beyond a certain limit they decompose and their structure and chemical properties are lost. Once decomposed, they cannot recover their initial state upon cooling. Their structure has many cross-links, which prevent the molecules from moving freely.