Surface modification of glass fibers for flame retardant and reinforced polyamide 6 composites

Glass fiber (GF) reinforced polyamide 6 (PA6) is a widely used composite. However, the GFs act as candlewick in burning, as a result, the PA6 continues burning after ignition. In this work, a novel flame retardant spirocyclic phosphate ester aminosilane (SPEA) was prepared, and it was self-crosslinked on the surface of the GF. The coated GF (SPEA-GF) was used with red phosphorus (RP) together in PA6. The flammability evaluation demonstrated that the PA6/SPEA-GF/RP (mass ratio of 64.5/30/5.5) composite passed the UL-94 V-0 grade in the vertical burning test, and the LOI value reached 30.5%. In the cone calorimeter test, the peak heat release rate (pHRR) of the PA6/GF (70/30) sample was 622 kW/m2; for the A6/SPEA-GF/RP sample, pHRR was sharply reduced to 356 kW/m2. Furthermore, the tensile, flexible, and impact strength of the PA6/SPEA-GF/RP composite were nearly equal to that of the PA6/GF (70/30) sample. This work provided a feasible solution to enhance the flame retardancy and mechanical performance of PA6/GF composites simultaneously.