Preparation and Thermal Properties of Novel N-arylpiperazine Phosphoramidate Flame-Retardant PS Copolymer

The inflammability of polystyrene (PS) limited its application. In order to improve the flame retardancy of PS, developing reactive-type flame retardants is a promising approach. In this work, a novel N-arylpiperazine phosphoramidate monomer, 2-((phenoxy(4-phenylpiperazin-1-yl)phosphoryl)oxy)ethyl methacrylate (PPPEM), was facilely synthesized and used as a reactive-type flame retardant. The obtained monomer was then copolymerized with styrene through the free radical bulk polymerization. The thermal stability of copolymers was measured by the thermogravimetric analysis. The addition of the PPPEM units increased decomposition temperature of the copolymers, indicating the improvement of the thermal stability. The glass transition temperature of the copolymers remained little changed with varied amount of the PPPEM, implying that the introduction of PPPEM units did not evidently affect the mobility of the PS main chain. The flammability of the copolymers was evaluated by microscale combustion calorimeter (MCC) and limiting oxygen index (LOI). According to the MCC and LOI results, PPPEM unites can contribute to the decrease of the peak heat release rate, the increase of LOI and improvement of the flame retardancy. The novel N-arylpiperazine phosphoramidate monomer show a great potential for application in reactive-type flame retardants.