Effect of matrix composition on properties of polyamide 66/polyamide 6I-6T composites with high content of continuous glass fiber for optimizing surface performance

Abstract To optimize the surface performance of the composites of polyamide 66 and continuous glass fiber (50/50, weight ratio), poly(hexamethylene isoftalamide-co-terephthalamide) (PA6I-6T) was introduced. The composites were prepared by a twin-screw extruder, and the effect of PA6I-6T on the thermal and mechanical properties, as well as surface appearance was investigated. The results showed that the crystallization temperature and the melting point of the composites decreased with increasing the amount of PA6I-6T. The Jeziorny method proved that the presence of PA6I-6T did not change the nucleation mode and the crystal growth of PA66 in the hybrid matrix, and the Mo method revealed that the crystallization rate of PA66 decreased first and then increased with the increase of the PA6I-6T content. The reduction in the “floating fiber” on the surface of the composites was attributed to the decrease of the crystallization rate of PA66 in the presence of PA6I-6T. It was shown that the composites with smooth surface had a large melt flow index. Moreover, the composites with high content of PA6I-6T had low heat deformation temperatures. The mechanical properties of the composites did not change significantly with the increase of the PA6I-6T content. Scanning electron microscope (SEM) images revealed that glass fiber was evenly distributed in the matrix and strongly oriented parallel to the injection direction.