Relationship study between crystal structure and thermal/mechanical properties of polyamide 6 reinforced and unreinforced by carbon fiber from macro and local view

Under effect of annealing and reinforcement of carbon fiber (CF), the relationship between crystalline structure of polyamide 6 (PA6) and thermal/mechanical properties was well studied. A local thermal analysis (LTA) method was applied for detecting interface properties between CF and PA6. Significant enhancement of thermal properties of PA6 with annealing and CF reinforcement was confirmed by thermal conductivity, HDT, and tanδ-T DMA curves, which was related with 112% crystallinity improvement by annealing and 105% improvement by CF reinforcement, and crystalline structure variation partly. In LTA results, thermal property near the CF area was improved due to a transcrystalline layer formation, which indicates LTA has great potential to be applied on the interface analysis in composites. Furthermore, flexural strength and modulus got a different degree of improvement by CF, as well as the storage modulus and impact strength, which proved the effective enhancement of strength and toughness of PA6 with strengthening of CF.