Influence of Mould Temperature on the Thickness of a Skin Layer and Impact Strength in the Microcellular Injection Moulding Process

Abstract

The thickness of a skin layer on the parts made by a microcellular injection moulding process may influence its properties, including impact and tensile strength, density and sound transmission. Therefore it is necessary to study the variations in skin layer thickness with processing parameters.

In this paper, the influences of temperatures in the mould cavity on the skin layer's thickness are addressed. In addition, the relationship between the temperature distributions across the cavity of the mould, with impact strength on parts made using a microcellular injection moulding process, was addressed. ^*T_SL, the temperature at which the skin layer forms, was proposed. According to previous studies, T_SL is expected to be similar to the polymer melting point for semi-crystalline polymer and the glass transition temperature for amorphous materials. In addition, a method to predict variations in skin layer thickness with mould temperature is discussed.