Question

Define thermoplastics and thermosetting polymers with two examples of each.

Answer 1

These two are two different types of polymers that are classified on the basis of the intermolecular forces present in them. They are widely different from one another hence having widely different characteristics and hence are used for different purposes in our day to day life.

Complete step-by-step answer: Thermoplastic polymer, is a plastic polymer material that becomes pliable or mouldable at a certain elevated temperature and solidifies upon cooling. These are linear or slightly branched long chain molecules possessing intermolecular forces of attraction intermediate between elastomers and fibres, which weaken rapidly with increased temperature $($implying they have low melting point$)$, yielding a viscous liquid. In this state, thermoplastics may be reshaped and are typically used to produce parts by various polymer processing techniques such as injection moulding, compression moulding, calendaring, and extrusion. Most thermoplastics have a high molecular weight but the molecular weight is lesser compared to thermosetting polymers. Thermoplastic polymers can be synthesized by the process of addition polymerization and they have low tensile strength. Some common thermoplastics are polythene, polystyrene, etc.
A thermosetting polymer, is a polymer that is irreversibly hardened by curing from a soft solid or viscous liquid pre-polymer. These polymers are cross linked or heavily branched molecules, which on heating undergo extensive cross linking in moulds and again become infusible $($implying they have high melting points$)$ and hence cannot be reused. Thermosetting polymers are processed by compression moulding, reaction injection moulding. They have high molecular weight, more than thermoplastic polymers. Thermosetting plastics are synthesized by condensation polymerization and have high tensile strength. Some common examples are Bakelite, urea-formaldehyde etc.

Note: Many students confuse between thermoplastic polymers and thermosetting polymers and by mistake write the definition of thermoplastic polymer in thermosetting polymer and vice-versa. Do take care of this fact and write the definitions and examples correctly corresponding to the correct polymer.