Injection Moulding of Thermosetting Materials

Nowadays, the injection moulder can be supplied with uniform quality granules which consist of partially polymerised resin, fillers and additives. The formulation of the material is such that it will flow easily in the barrel with a slow rate of polymerisation. The curing is then completed rapidly in the mould. 

In ntosl respects the process is similar to the injection moulding of thermoplastics and the sequence of operations in a single cycle is as described earlier. For thermosets a special barrel and screw are used. The screw is of approximately constant depth over its whole length and there is no check value which might cause material blockages (see Fig. 4.50). The barrel is only kept warm (80-110°C) rather than very hot as with thermoplastics because the material must not cure in this section of the machine. Also, the increased viscosity of the thermosetting materials means that higher screw torques and injection pressures (up to 200 MN/m are needed). 

For the same part, injection moulding of thermosets can offer up to 23% production increase and lower part-costs than compression. 

Injection moulding Unload piece, open/close machine 0.100 

The term thermoforming incoroporates a wide range of possibilities for sheet forming but basically there are two sub-divisions - vacuum forming and pressure forming. 

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Injection moulding of thermosetting materials is achieved in the same way as for thermoplastic materials except that the temperatures used are more critical. The temperature of the heating chamber is... 

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