Two-component injection moulding of thermoplastics with thermoset rubbers: The effect of the mould temperature distribution

Abstract

In a previous study [1] a novel two-component injection moulding process was proposed for combining thermoplastics with thermoset rubber. This process requires moulds in which the cavities for the thermoplastic and the rubber are thermally separated making it possible to use different mould temperatures for both materials. The process starts by first injecting the thermoplastic part. Afterwards the thermoset rubber is injected and vulcanised. The goal of two-component injection moulding is to combine materials within a single product without assembly. Therefore the adhesion strength between the two materials is an important property that detennines the product quality for a two-component injection moulded product. A second important property for every injection moulding process is the cycle time. The cycle time for this specific process is mainly determined by the time required to sufficiently vulcanise the rubber. In this paper the effect of the mould temperature on both the adhesion strength and the vulcanisation time arc investigated experimentally. Products are produced using different mould temperature distributions. Afterwards the adhesion strength is examined using tensile tests. The vulcanisation time is detennined by using hardness measurements to verify the vulcanisation degree of the rubber. Results indicate that higher mould temperatures for the thermoplastic part lead to higher adhesion strength and lower vulcanisation time.