ON THE LINKAGE OF SILOXANES WITH EPOXY-RESINS .3.

By means of Brabender measurements, the curing behaviour of fused silica filled Me-Ph-silicone phenol novolak epoxy resin moulding materials was investigated. Al(acac)3 and Al(benzoate)3 were used as catalysts. The binder-mixture ratio was varied from 60 to 20% of silicone resin and 40 to 80% of epoxy resin. Using the less active Al(benzoate)3 as the catalyst, technically acceptable duration of processability t(v) and sufficient crosslinking density was ensured. In the range of 40 to 30% silicone resin and 60 to 70% epoxy resin the activation energies E(A) remained equal. The E(A) values for the moulding materials containing filling substances are between 50 and 52 kJ mol-1 and are distinctly higher than those for binders containing no filling substances of about 30 kJ mol-1. However, the course of E(A) values in dependence on the composition of the binder is independent on the filler percentage. Hence, it is concluded that polymer formation reactions are only negligibly influenced by the filling substance. The findings show that the methodically simple measurements of gelling time and DSC measurements cannot only be used to evaluate binders but also to select moulding materials as well.