Experimental characterisation and modelling of rheokinetic properties of different silicone elastomers

Elastomer injection moulding is a process whereby an elastomer mix is injected into a closed mould where the material is shaped to the desired geometry. Once completely filled, the silicone elastomer mix is vulcanised. Vulcanisation is the process whereby a viscous flow of silicone is converted into an elastic material through the incorporation of chemical cross-links between the material chains. To correctly use simulation tools to predict the filling of die mould cavities, it is necessary to characterise the material in terms of their rheological properties and kinetic behaviour during curing. The aim of this study was to develop mathematical models for the thermo-kinetic parameters of elastomers that can properly predict the filling of the die mould cavity. In this work, a rotational rheometer was used to determine changing viscosity and vulcanisation characteristics of a silicone compound. The rheokinetic properties of different silicone fluid samples were measured over a broad temperature range from 25 to 100 A degrees C and are reported in this paper. Good agreement was obtained between the experimental results and the model predictions. The methods proposed could well represent the overall experimental data for different silicone elastomers; thus, it could be readily employed for simulation of the elastomer injection moulding process.