Preparation of flame retardant glass fiber via emulsion impregnation and application in polyamide 6

Abstract As a commonly used reinforcement, glass fiber (GF) can improve the mechanical properties of thermoplastics. However, previous studies have suggested that GF was not good for the flame retardancy of thermoplastics because of “wick effect.” Herein, a novel flame retardant emulsion was synthesized, containing film-former, lubricant, silane coupling agent, and ammonium polyphosphate modified by 3-aminopropyltriethoxysilane (mAPP). The GF impregnated with flame retardant emulsion and aluminum diethlyphosphinate (ADP) were blended with polyamide 6 (PA6) to prepare flame retardant GF reinforced PA6 (FRGFPA6/ADP). The LOI of FRGFPA6/ADP-15 can reach 34.7%, which is much higher than that of GF reinforced PA6 (GFPA6) and it also pass the UL-94 test and reach V-0 rating without dripping. The mHRR, pHRR, and THR of FRGFPA6/ADP-15 are reduced by 44.2, 121.0, and 26.3% compared to GFPA6. After burning, the surface of flame retardant GF can form a carbon layer, which improved the efficiency of interfacial flame retardancy between GF and PA6 and weakened the “wick effect.” At the same time, ADP is added to the matrix to release free radicals to capture oxygen in the air, and carbon layer is formed to isolate the air. The synergistic effect of ADP and mAPP increased the flame retardancy of GFPA6.