Modelling Cure Times for Thermoset-Thermoplastic Injection Moulding

Thermoplastics and thermosets have very different temperature requirements which pose a problem when processing them together in multi-material parts. This paper examines the time available for the cure of a thermoset material in a thermoplastic injection moulding environment. It uses thermal equations to form a basic physical model of the temperature profile during the cooling stage within an injection moulding cycle. The model explores the different cooling times provided by using different thermoplastic substrates and the heat available from each of these to cure the thermoset component during a standard cycle. Thermal analysis of commercially available thermoset materials was undertaken and compared to the model results to determine if cure could be obtained in-mould. It was found that the properties and processing conditions of PA66 provided the greatest heat exposure to the thermoset material; it was also found that temperatures within the mould are high enough to initiate cure however only within the proximity of the thermoplastic – thermoset boundary. A result of this effect is to produce a novel in-to-out cure mechanism that produces a thermoplastic-thermoset-thermoplastic structure with the potential application as a barrier layer.