Flame retardancy of thermal conductive polyamide 56 composites regulated by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivative and polyoxometalate

The thermal conductivity of PA56 composites is 283% higher than that of PA56. • Surface modification enhances the flame retardancy of PA56. • Nickel phosphomolybdate improves the flame-retardant efficiency of PA56. • PA56 with good thermal conductivity and flame retardancy are achieved. Flame retardancy of polymer is often deteriorated when its thermal conductivity (TC) is increased. In this paper, alumina (Al 2 O 3 ) and boron nitride (BN) were modified and applied to increase the performance of polyamide 56 (PA56). The 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivative (DiDOPO) and nickel phosphomolybdate (PMoNi) were compounded as a flame-retardant system for PA56. The TC for PA56 samples is increased to 0.92 W/(m·K) which is 283% higher than the TC of PA56. 6 wt% DiDOPO endows PA56 with a UL-94 V-2 rating, while the PA56 containing the same amount of DiDOPO/PMoNi (5:1) obtains the UL-94 V-0 and a limiting oxygen index of 34.2 vol%. The char layer generated by PA56 and the thermal conductive fillers show some blocking effect, effectively inhibiting the release of heat, smoke from PA56 during combustion. DiDOPO works in gas and condensed phase, and the former dominates; PMoNi helps PA56 to form char layer with high quality, which enhances the scavenging effect and improves the flame-retardant efficiency. PMoNi improves the flame retardancy of thermally conductive PA56 by enhancing the scavenging effect. Download: Download high-res image (180KB) Download: Download full-size image