| Abstract: | Mineral fillers of flake configuration such as mica can, in principle, produce large increases in modulus and strength especially if the flake is oriented predominantly in a plane. Additionally, the resulting composites have the advantage of possessing isotropic properties in the plane of orientation, thereby minimizing the warpage normally associated with the injection molding of fiber-reinforced thermoplastics. However, to properly transmit stress from the matrix to the mica and minimize the effect of defects in morphology, a ductile matrix is required with adequate interaction or adhesion between phases. Many of the above conclusions are documented in the literature and are confirmed by our investigations of the system mica-polypropylene. The novelty of this effort rests upon (1) successful attempts to identify specific non-silane additives which by co-blending suitably modify the mica-polypropylene interface, (2) to demonstrate the remarkable effects of time-temperature during melt processing on the behavior of this system; and, (3) to show the relation between composition and time-temperature effects on resultant mechanical, physical, and thermal properties. Most notably, large improvements in tensile and flexural strength and heat distortion temperature can be attributed to the use of small amounts of chlorinated organic compounds blended under carefully selected melt process conditions. Some speculation concerning the mechanism of interaction will be discussed and the resultant potential for increased application will also be outlined. |
