Interfacial instabilities in multimaterial co-injection mouldings Part 1 ~ Background and initial experiments

Interfacial adhesion between the skin and core is vital for successful co-injection moulding. This is the first paper in a series, which introduces and describes an in mould method of mixing that is applicable regardless of the compatibility of the materials. It works by inducing turbulent mixing at the interface between the skin and core materials. It makes use of the change that occurs from laminar to turbulent flow at high injection speeds in co-injection moulding. This novel approach takes advantage of the moulding parameters already available within the co-injection system to offer an expanded range of material combinations for multimaterial moulding. Comparisons are made between multimaterial mouldings made with miscible polymers, immiscible polymers with no compatibiliser, and immiscible polymers bonded by compatibilisers.