Thermoset Processing Forms

What is a Thermoset?

Thermoset plastics, or thermoset composites, are synthetic materials that strengthen when heated, but cannot successfully be remolded or reheated after initial heat-forming or molding. After thermosets are molded, the resulting parts offer protection against high operating temperatures, corrosion, and chemical resistance.

These material property benefits allow molded thermoset parts to be used in a variety of aggressive and challenging end-use environments, from electrical applications to automotive powertrain and transmission components to products with outdoor element exposure.

Using a thermoset molding process allows final parts and assemblies to remain dimensionally and chemically stable against elements such as moisture, high heat or operating temperatures, electric voltage, and chemicals or automotive fluids.

Sometimes, polymer materials must be reinforced with fibres if they are to be used structurally and in so doing a wide range of composites with varying mechanical properties may be obtained by altering:

  1. the relative proportions of thermosetting polymers and fibres;
  2. the type of each component employed;
  3. the fibre orientation within the resin matrix;
  4. the method of manufacture of the composite.

The fibre orientation within the matrix will be dependent on the type of reinforcement used; consequently, it will be clear that the three main types of composites which can be manufactured will depend on whether unidirectional strand, bidirectional strand or cloth, or chopped strand mat reinforcement is used.

Processing methods for the manufacture of reinforced thermosetting polymers

There are various techniques for the manufacture of fibre reinforced thermosets; these methods may be considered under three headings:

  • the manual process;
  • the semi-automatic process;
  • the automatic process.

The manual process covers methods such as hand lay-up, spray-up (both of which are known as contact moulding), pressure bag and autoclave moulding.

The semi-automatic process includes cold pressing, compression moulding and resin injection.

The automatic processes are those such as pultrusion, filament winding and injection moulding.


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