Compression molding is a process of molding in which a feeding material is placed into an open, heated mold cavity. The mold is then closed with a top plug and compressed with large hydraulic presses in order to have the material contact all areas of the mold. The charge cures in the …
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:
- the relative proportions of thermosetting polymers and fibres;
- the type of each component employed;
- the fibre orientation within the resin matrix;
- 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.
Thermoplastics Processing Methods Thermoplastics are materials which soften when heated and can then be formed whilst soft. After cooling they becoming rigid take up the applied form. The softening and forming processes are reversible. Thermoplastics are probably the most widely used type of polymer. The group includes most of the “commodity” plastics …
Introduction Thermosets refer to the set of materials formed by polymers joined by chemical bonds acquiring a highly cross-linked final structure. The highly cross-linked structure of thermoset materials is directly responsible for the high mechanical and physical resistance (stresses or loads, temperature…) of these materials compared to thermoplastics and elastomers. On the …