THERMOPLASTIC POLYOLEFINS (TPO) FOR SLUSH MOLDING OF INTERIOR SKINS: MATERIALS AND PROCESSING REQUIREMENTS

摘要

Slush moldable TPO compositions have been formulated to possess the required balance of low melt viscosity under the low shear rates expected during rotational molding. Low temperature ductility is imparted by suitable choice of a low T_g polyolefin elastomer that forms a dispersed phase in an essentially semi-crystalline matrix. Different elastomers can be used to change the handling characteristics of the skin, however, the composition dependent rheology of the formulations can have an adverse effect on melt viscosity. A thermodyanamic analysis of miscibility in some of these blends has also been described which is used to explain experimentally observed morphological, rheological, and thermal properties of the compositions investigated and also used to indicate how appropriate materials may be selected. Cryogenic pulverization of melt compounded compositions has been used to develop powders of the required particle size distribution that make them suitable for slush molding using existing equipment. Powder flow, particle size and temperature are important parameters that will affect skin quality.