Thermoplastics

Thermoplastics are polymers with Chain or thread-like macromolecules that exhibit weak intermolecular bonding. They become soft when subjected to heat and can therefore be moulded and formed. On cooling, the workpieces retain their shape, however the process can be reversed by reapplying heat.

Thermoplastics can be used above or below the Glass transition temperature depending on their application and molecular structure.

• Amorphous, usually hard and brittle thermoplastics are used in applications where temperatures are below the temperature at which the mass hardens without crystallising.
• Partially crystalline thermoplatics with parallel molecule chains are used when temperatures exceed the glass transition temperature.

Thermoplastics with a similar melting index can be welded by applying pressure and heat. They are often used in Injection moulding, Extrusion and blow moulding processes. Calendering and blown film extrusion can also be used. Thermoplastics are generally also suitable for mechanical and thermal processing, e.g. Sawing, Grinding, Planing and Milling and thermal treatments such as in vacuum Deep-drawing.

Types of thermoplastic include:

• Polyethylene
• Polyvinyl chloride
• Polypropylene
• Polyamides
• Polystyrene
• Polyester
• Polyblends