Examining the thermal behaviour of novel aromatic polybenzoxazine blends containing an organophosphorous compound and polyhedral oligomeric silsesquioxane reagents

2,2-Bis(3,4-dihydro-3-phenyl-2H-1,3-benzoxazine)propane (BA-a) is blended with different commercial polyhedral oligomeric silsesquioxane (POSS) reagents and an organophosphorous compound bis(4-hydroxyphenyl)phenylphosphine oxide (BPPO), at a range of loadings (1 – 10 wt %). The influence of the additives on the onset and a rate of polymerisation of the BA-a is examined using differential scanning calorimetry. An initial screen of blends containing various additives (5 wt%) shows that a combination of aminoethylaminopropyl isobutyl POSS (AEAP) and BPPO has the greatest effect on reactivity with a reduction in reaction onset of some 65 K and an increase in T_g of 18 K when compared with the BA-a homopolymer. The activation energy for the polymerization of BA-a containing 5 wt% AEAP was determined to be 84-88 kJ/mol (using Kissinger and Ozawa kinetic models), with a first order rate constant of 1.9 x 108 s^-1. The thermal stability of the cured blends containing 5 wt% flame retardant were examined using thermogravimetric analysis (TGA) and both onset of degradation and char yield are increased by 15 K and 5 % respectively when compared with the BA-a homopolymer.