The influence of processing conditions on the aesthetical, morphological and mechanical properties of SF mouldings of high-impact polystyrene (HIPS-SF)

Abstract

The production of large plastic parts, in small series and at low cost, requires the development of alternative tools and materials. Structural foams (SF) are a good solution, when the production of thicker parts with good properties is the specification. They allow obtaining lightweight parts with high stiffness and good dimensional stability, due to their sandwich-like structure constituted by a cellular core and two solid skins. The porous core results from the addition of a blowing agent in the polymeric matrix. These materials are applied in urban furniture, automotive, nautical and aerospace industries. The most used process to produce SF is the low pressure foam moulding, which is a short shot process, with impression pressures ranging from 1.4 to 4 MPa. Thus, the use of hybrid moulds with moulding blocks obtained by rapid prototyping routes is seen as a viable alternative for SF injection moulding. This work reports on a study of the influence of processing conditions on the aesthetical, morphological, and mechanical properties of SF mouldings of high-impact polystyrene (HIPS-SF). The results compare the effect of the use of hybrid moulds to conventional moulds on the surface aspect of the circular centre gated mouldings. Furthermore the influence of the moulding temperature is ascertained in terms of the resulting cellular morphology, the flexural stiffness of the plate mouldings, and the impact resistance in the instrumented drop weight test.