The Effects of Nitrogen-Containing Monomers on the Thermal Degradation and Combustion Attributes of Polystyrenes Chemically Modified With Phosphonate Groups

In the present study, polystyrene (PS) is chemically modified with diethyl(acryloyloxymethyl)phosphonate (DEAMP) and an N-containing monomer, selected from different classes of compounds, via a ter-polymerization route; thus, exploring possible P–N synergistic effects on fire retardance of the base polymer. The successful incorporation of P and N monomeric units is confirmed by Fourier Transform Infrared (FT-IR), ¹H and ³¹P Nuclear Magnetic Resonance (NMR) spectroscopies. The thermal degradation and combustion attributes of modified polymeric materials are measured using standard techniques, including Thermo-Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), “bomb” calorimetry, and Pyrolysis Combustion Flow Calorimetry (PCFC). The thermal and combustion studies demonstrate that the thermal stability and combustion characteristics of styrenic polymers are significantly altered by the presence of even nominal amounts of P- and N-containing groups, and in certain cases, synergistic interactions of these groups are also evident. For instance, as revealed by TGA, the extent of char formation, under the oxidative atmosphere, in the prepared ter-polymers, is enhanced by 16–44%, when compared to the unmodified PS. The heat release rates and heat release capacities of ter-polymers, measured using the PCFC technique, are reduced by 18–50%, in comparison to the same parameters obtained for the unmodified counterpart.