para-Aramid fiber modified by melamine polyphosphate and its flame retardancy on thermoplastic polyurethane elastomer

Abstract

With the increasing applications of thermoplastic polyurethane elastomer (TPU), the fire risk and smoke hazard caused by TPU have aroused wide attention. At the same time, with the promotion of aramid fiber in industry, the waste and pollution caused by aramid fiber is becoming worse. Herein, para-aramid fiber (AF) is recycled and modified by melamine polyphosphate (MP), and then applied as a flame retardant for TPU. The flame retardant and smoke suppression properties of the TPU composites are determined using the limiting oxygen index (LOI), cone calorimeter test (CCT), smoke density test (SDT) and thermogravimetric/Fourier transform infrared spectroscopy (TG-IR). The LOI test shows that the thermal stability of TPU is further improved by AF-MP. The CCT test shows that AF-MP has a better flame retardant and smoke suppression effect on TPU than pure AF. Remarkably, the pHRR and THR value for the sample with 1.00 wt% content of AF-MP decreased by 38.1% and 24.5% compared with that of the pure AF sample, where the residual mass of AF-MP was more than that of the AF sample. The SDT test shows that AF-MP has a better smoke suppression property in TPU than pure AF, particularly in the absence of a flame. The TG-IR test reveals that AF-MP further promotes the char forming process during combustion. Thus, this investigation presents great insight into the study of reusing fibers and efficient flame retardant polymers.