Studies of microcellular nanocomposites with supercritical fluid assisted injection moulding process

Abstract

In this study, the microstructure, thermal behaviour and mechanical properties of microcellular nanocomposites were studied. Microcell wall structure and smoothness were determined by the size of the crystalline structure, which, in turn, was based on the material system and moulding conditions. Nanoclay in the microcellular, supercrtitical fluid assisted injection moulding process promoted the γ form and suppressed the α form crystalline structure of polyamide 6 (PA6). In the crystallisation kinetics studies, the Avrami equation and the modified Ozawa equation with the Mo method were used to model and analyse isothermal and non-isothermal crystallisation processes respectively. The existence of nanoclay increased the magnitude of the activation energy for both isothermal and non-isothermal crystallisation processes. This suggests the fast crystallisation process and the small crystalline size for microcellular nanocomposite processing. Interestingly, the dissolved gas lowered the crystallinity of the cores of moulded microcellular parts, but the addition of nanoclay reduced the crystallinity of both the cores and the skins of parts. The collective effect of the dissolved gas and nanoclay acted to shorten the moulding cycle time greatly with a reduction in the overall crystallinity of microcellular nanocomposite parts.