Semiaromatic polyamide poly(hexamethylene terephthalamide)-co-polycaprolactam: Thermal and flame-retardant properties

The poly(hexamethylene terephthalamide)-co-polycaprolactam (PA6T/6; 50:50) copolymer was synthesized with a reactive extrusion method and subsequently mixed with a certain content of glass fibers (GFs) and different ratios of flame-retardant aluminum diethyl phosphinate (AlPi) to fabricate a series of composites. These resulting composites were found to have excellent mechanical (tensile strength=119-154 MPa) and thermal properties (heat-deflection temperature=263-293 degrees C). It is particularly worth mentioning that the value of the limiting oxygen index reached 29.5% and a UL-94 V-0 rating (1.6 mm) was achieved with the addition of 20 portions of AlPi. Also, the values of the peak heat-release rate and total heat release in cone calorimetry were found to decrease with the addition of the flame-retardant AlPi, which acted mainly as a flame inhibitor in the gas phase. Through visual observation, scanning electron microscopy after cone calorimetry testing, and thermogravimetric analysis, the condensed-phase flame-retardant mechanism of the PA6T/6-GF-AlPi system was confirmed to have a synergetic role. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46451.