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Plastic Material Properties
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Plastic Material Properties
Thermoplastics
- Formed by chain-growth polymerisation
- Solid at room temperature
- Melted or softened by heating
- placed in a mould or shaping device and are then cooled to give desired shape
- High strength and stiffness
- Can be reinforced
- Holds mechanical properties up to around 80 degrees
- Good impact resistance
- Dimensional stability within temperature range
- Good water and chemical resistance
- Easy to shape to desired forms
- Extrusion - continuous 2D shaping process used for wires, films and pipes
- Injection Moulding - discontinuous process capable of generating complex 3D shapes
- Extrusion Blow Moulding - for small and medium sized containers and bottles
- Rotational Moulding- used for hollow parts manufactured at low production size
Thermosets
- Formed by step-growth polymerisation
- Can be liquid or solid at room temperature
- Cannot be reshaped by heating
- Placed in a mould and then heated to harden (cure) then the chemical reaction occurs
- Phenolics noted for high hardness and stiffness
- Can replace hard materials like Ivory
- Amino plastics are hard and brittle
- Can be used as adhesives or countertops
- Epoxides are stiff and strong
- Can be used as adhesives for composite materials
- Polyurethanes can be designed with different strength vs flexibility
- Good abrasion resistance
- As well as the forming operation this requires reactive processing of the polymer with a curing agent, this can be done as high or low pressure moulding
- Compression Moulding - polymer mixed with the curing agent is pressed at high pressure into a closed mould