Properties and morphology of polyamide 6 hybrid composites containing potassium titanate whisker and liquid crystalline copolyester

Polyamide 6 (PA6) hybrid composites reinforced with potassium titanate whiskers (K2Ti6O13) and liquid crystalline polymer (LCP) were prepared in a twin-screw extruder followed by injection moulding. The whiskers were surface treated with tetrabutyl orthotitanate prior to blending. Static tensile measurements showed that the tensile strength and modulus of the composites tend to increase with increasing whisker content. However, Izod impact tests indicated that the hybrid composites show little variation in the impact strength with the addition of whisker content up to 10 wt%, thereafter the impact energy shows an obvious decrease with increasing whisker content. Scanning electron microscopic observations revealed that the oriented LCP fibrils were formed in the skin section of hybrid composites containing whisker content < 10 wt%, whilst spherical droplets were dispersed in the skin section of hybrids containing whisker content greater than or equal to 15 wt%. Torque measurements showed that the LCP is very effective in reducing the melt viscosities of PA6/K2Ti6O13 composites. Finally, thermogravimetric analysis showed that the hybrid composites with higher whisker content exhibit good heat resistance properties. The hybrid effects of the two reinforcements on the mechanical properties and compatibility of these hybrid composites are discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.