Preparation of Salen-based polyphosphoronitrile microspheres composite LDH and study of epoxy composite properties

Abstract

This paper describes the preparation of organic-inorganic hybrid flame retardants obtained by compositing Salen-based polyphosphonitrile microspheres with layered double hydroxide (LDH) phases. The flame retardants were applied to the effects of varying the mass ratio of the two materials on the flame retardancy of EP composites and were compared with the mass ratios of 1:2, 1:1 and 2:1, respectively. The results demonstrated that the Salen-PZN-Ni@LDH (2:1)/EP composites synthesized when the mass ratio of the two components was 2:1 exhibited enhanced thermal stability and flame retardant properties. The incorporation of 9 wt.% Salen-PZN-Ni@LDH (2:1) resulted in residual carbon rates of 28.92% at 800°C, an LOI value of 28.8%, a UL-94 test to achieve a V-1 rating, and a reduction in smoke release rate (PSPR) and heat release rate (PHRR) compared to pure EP. The values obtained were 35.6% and 44.0%, respectively. The flame retardant plays a dual role in both the gas phase and the condensed phase, enhancing the thermal stability of EP composites. This finding presents a plethora of avenues for research, particularly in the domains of multifunctional flame retardants and flame retardant materials, characterized by high flame retardant efficiency, minimal economic cost, and a minimal environmental footprint.