Thermal and Calorimetric Evaluations of Polyacrylonitrile Containing Covalently-Bound Phosphonate Groups

One of the effective ways to enhance flame retardance of polyacrylonitrile (PAN) is through a reactive route, primarily developed in our laboratories, which involved chemical modification reactions utilising phosphorus-containing comonomers. In the present study, diethyl(acryloyloxymethyl)phosphonate (DEAMP) and diethyl(1-acryloyloxyethyl)phosphonate (DE1AEP) were synthesised and copolymerised with acrylonitrile (AN), under radical initiation in an inert atmosphere, in aqueous slurries. The thermal degradation and combustion characteristics as well as the extent of flame retardation were mainly assessed with the aid of various thermo-analytical and calorimetric techniques. It was found that the incorporation of phosphonate groups in polymeric chains of PAN resulted in improved flame-retardant characteristics. Furthermore, it was observed that the actual chemical environment of the phosphorus atom in the acrylic phosphonate modifying groups has little effect on the overall thermal degradation and combustion behaviours of the modified PAN systems. It was also observed that the predominant mode of flame retardance occurred in the condensed phase.