1. Thermoplastic Polymers
- Definition: Polymers that soften when heated and harden when cooled. This process can be repeated many times without chemical change.
- Structure: Long linear or slightly branched chains without cross-linking.
- Properties: Flexible, can be reshaped or recycled.
- Examples: Polyethylene, polypropylene, polystyrene, PVC.
- Uses: Packaging materials, bottles, toys, pipes, and containers.
2. Thermosetting Polymers
- Definition: Polymers that harden permanently when heated or cured. Once set, they cannot be remelted or reshaped.
- Structure: Highly cross-linked three-dimensional network.
- Properties: Strong, rigid, heat-resistant, not recyclable easily.
- Examples: Bakelite, melamine, epoxy resins, urea-formaldehyde.
- Uses: Electrical fittings, adhesives, laminates, cookware handles.
Key Difference:
- Thermoplastics can be reheated and reshaped, while thermosetting polymers cannot be reshaped after setting.