The influence of processing conditions on tensile properties of wholly thermoplastic composites reinforced with nanotubes

摘要

This paper is concerned with novel wholly thermoplastic composites (WTCs) reinforced with supercritical carbon dioxide-aided exfoliated multi-walled carbon nanotubes (MWCNTs) and the enhancement of mechanical properties. The bicomponent in situ injection molded plaques consist of polyamide 6 (PA6) and microfibers of thermotropic liquid crystalline polymer (TLCP) with miss-matched melting temperature. Multiple mixing histories with MWCNTs and processing temperatures were studied and tested for minimizing matrix thermal degradation and maximizing tensile properties of the multi-scale WTCs. The optimum in situ injection molding temperature was found at 300 degrees C with melt blending nylon 6 matrix and exfoliated MWCNTs in advance. Exfoliated MWCNTs acted as bridging elements between the TLCP and the nylon 6 matrix, which lead to effective stress transfer from the nylon 6 matrix to the TLCP fibrils. Compared to the WTCs without MWCNTs reinforcement, tensile modulus and tensile strength in longitudinal and latitudinal directions were both improved. Furthermore, with the reinforcement of TLCP and exfoliated MWCNTs, the tensile modulus and tensile strength of nylon 6 were enhanced by 173% and 35% in the fluid flow direction, respectively. These experimental results for 20 wt% TLCP/PA6 were even better than the mechanical properties of 20 wt% carbon fiber (CF)/PA6 reported in the literature.