Thermal Decomposition of Styrenic Polymers Modified with Covalently Bound P- and N-containing Groups: Analysis of the Gaseous-Phase Mechanism

Through the present study, we have modified polystyrene chains by chemically binding nominal amounts
of P- and/or N-containing monomers via a free radical polymerization. The selected monomers included:
diethyl(acryloyloxymethyl)phosphonate (DEAMP), diethyl-p-vinylbenzyl phosphonate (DEpVBP), acrylic
acid-2-[(diethoxyphosphoryl)methylamino]ethyl ester (ADEPMAE) and maleimide (MI). The purpose of
these chemical modifications was to enhance the fire retardance in the resultant co- and ter-polymers
prepared via a solution polymerization technique. Thermogravimetric (TGA) and pyrolysis combustion
flow calorimetry (PCFC) investigations found that the modified systems exhibited an improved propensity
to form char residues and had lower heat release rates, as compared to the control homopolymer.
Furthermore, pyrolysis/GC-MS was employed to identify the major volatile products formed upon the
thermal decomposition of the polymers. For instance, ethanol, benzaldehyde, acetophenone
triethylphosphate, as well as styrene and styrene oligomers were detected in the gaseous phase emanating
from the pyrolysis reaction(s) of the modified polymers, indicating a significantly altered decomposition
mechanism.