Mould heating process

Carbon fibre-reinforced polymer composites mould heating process... 

The main reason for extruding polystyrene is to prepare high-impact polystyrene sheet. Such sheet can be formed without difficulty by vacuum forming techniques. In principle the process consists of clamping the sheet above the mould, heating it so that it softens and becomes rubbery and then applying a vacuum to draw out the air between the mould and the sheet so that the sheet takes up the contours of the mould. 

Vacuum bag moulding (autoclave process) Prepreg is encased in flexible bag a vacuum is applied to draw the prepreg against a mould surface. Heat is applied. Process carried out in autoclave Very large structures prototypes short production runs high fibre content... 

Autoclave Moulding—A process similar to the pressure bag technique. The lay-up is covered by a pressure bag, and the entire assembly is placed in an autoclave capable of providing heat and pressure for curing the part. The pressure bag is normally vented to the outside. 

If this is the case, it would be necessary to remove all the water present in order to force the equilibrium completely toward diimine formation and the establishment of permanent cross-links. Experimental evidence for this proposition is that a full state of cure is not attained if the long heating process is carried out in the mould, i.e., in a virtually closed system. Hydrolysis is also demonstrated by the fact that much of the diamine present in a vulcanizate can be extracted by treatment with water. 

In plastics forming processes the basic polymer is heated until it flows, moulded into shape under pressure and finally cooled. In rotational moulding the whole of the process takes place inside a female mould. The process exploits the principle that finely divided thermoplastic material becomes molten in contact with a hot metal surface, and will take up the shape ol that surface. If the polymer is then cooled while still in contact with the metal a solid copy of the surface will be produced. 

The mould heating and the curing time influence the last phase of heat supply. Only a small amount of heat is fed to the melt in order to form the part and to complete the forming process. 

Fig. 24.5. Compression moulding the thermoset is squeezed to shape and cured (by heating) at the some time. Once it has cured it con be token from the mould while still hot - so the process is faster than the moulding of thermoplastics.

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