Plastic Material Properties

Plastic Material Properties

1. 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

2. 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