Q.Define thermoplastics and thermosetting polymers with two examples of each.

Thermoplastic polymers: linear or slightly branched long-chain polymer molecules that are capable of repeatedly softening on heating and hardening on cooling, with essentially no chemical change. Because the chains are held together only by intermolecular forces (not permanent chemical crosslinks), they can be melted and remoulded into different shapes multiple times.

Examples: Polythene and Polyvinyl chloride (PVC).

Thermosetting polymers: polymers that, on heating (or with a curing agent), undergo extensive irreversible cross-linking between chains to form a hard, rigid, infusible three-dimensional network. Once set, they cannot be softened or remoulded again by reheating — attempting to reheat them strongly causes decomposition/charring rather than melting. …

Define each class by its behaviour on heating (reversible softening vs irreversible cross-linking/curing) and structural basis (linear chains vs …

• Thinking thermosetting polymers 'melt' like thermoplastics — they actually char/decompose rather than melt on strong reheating.
• Mixing up which examples belong to which class (e.g., calling Bakelite a thermoplastic). …