Heizzeitverkürzung im Elastomerspritzguss durch Ausnützung des Effekts der Kompressionserwärmung

The curing time, in which the material is subjected to molecular cross linking, is the largest part of the complete cycle time of a rubber injection moulding process. The aim of this thesis is to use the effect of dissipation due to compression to heat up the material before it is injected into the cavity. This should reduce the incubation time as well as the heating time. The first part of this thesis was to calculate the increase of the temperature due to compression and validate the results in practical experiments on a high pressure capillary rheometer and an injection moulding machine. Therefor, two rubber materials (SBR and EPDM) were compressed at certain pressure levels and the temperature rise was measured. To investigate if the cycle time of an injection moulding process could be reduced by the effect of compression heating, an injection mould was constructed, to integrate a compression phase into the injection moulding cycle. With this mould rubber parts were produced by variation of compression pressure, compression- and curing time. To analyse the level of cross linking of these parts the hardness Shore A and the compression set were measured. The results showed for the chosen temperature level that the curing time could not be significantly reduced by the effect of compression heating. One reason is that the maximum reachable compression pressures in the shot volume of plasticising unit were too low to generate a sufficient temperature rise. Furthermore the effect of compression heating was partly compensated by heat loss due to heat conduction for high compression times.