Preparation and mechanical properties of long glass fiber reinforced PA6 composites prepared by a novel process

Long glass fiber reinforced PA6 (LGF/PA6) prepregs were prepared by impregnating PA6 oligomer melt into reinforcing glass fiber followed by subsequent solid-state polymerization (SSP) to obtain LGF/PA6 composite pellets. A conventional injection-molding machine suitable for short glass fiber reinforced composites was applied to the processing of the prepared composites, which reduced the fiber length in the final products. Mechanical properties, thermal property, and fiber length distribution of injection molding bars were investigated. Scanning electron microscopy (SEM) was used to observe the impact fracture surfaces and the surfaces of glass fiber after the SSR It was found that the LGF/PA6 composites were of favorable mechanical properties, especially the impact strength, although the average length of glass fiber was rather short. By this novel process, the content of glass fiber in composite could be high up to 60 wt.-% and the maximum level of heat distortion temperature (HDT) was close to the melting temperature of PA6. SEM images indicated the favorable interfacial properties between the glass fiber and matrix. The glass fiber surfaces were further observed by SEM after removing the matrix PA6 with a solvent, the results showed that PA6 macromolecules were grafted onto the surface. Furthermore, the grafting amount of PA6 was increased with SSP time.