Preparation of continuous glass fiber/polyamide 6 composites containing hexaphenoxycyclotriphosphazene: Mechanical properties, thermal stability, and flame retardancy

Abstract

AbstractThe halogen‐free flame‐retardant continuous glass fiber/polyamide 6 (GF/PA6) composites containing hexaphenoxycyclotriphosphazene (HPCTP) were prepared by the resin transfer molding (RTM) process. The influence of HPCTP content on mechanical properties of GF/PA6 composites was studied. The addition of HPCTP has no obvious effect on the tensile properties of composites, and the tensile strength of GF/PA6 composites with the addition of 30% HPCTP reaches 425.2 MPa. However, with the addition of HPCTP, the flexural strength and interlaminar shear strength of GF/PA6/30%HPCTP composites decrease to 246.4 and 20.9 MPa, respectively. The flame retardancy, thermal stability, and burning behavior of the composites were evaluated by means of limited oxygen index (LOI), UL‐94, thermogravimetric analysis and cone calorimeter. The results show that the LOI value of GF/PA6 composites can reach up to 30.9% corresponding to the grade of UL‐94V‐0 with the addition of 30% HPCTP. The flame retardancy mechanism of GF/PA6/30%HPCTP composites is attributed to the combined effects of releasing incombustible gases in gas phase at the early stage and forming char layers in the condensed phase, which can dilute the concentration of combustible gas and retard the mass and heat transfer.