Diglycidylphenylphosphate based fire retardant liquid crystalline thermosets

Organophosphorus liquid crystalline thermosets (LCTs) were developed using diglycidylphenylphosphate (DGPP) and various aromatic diamines. DGPP was prepared by the esterification of phenylphosphorodichloridate with glycidol. 2,5-Bis(p-aminophenyl)-1,3,4-oxadiazole (BPOD) was synthesized and three different commercial diamines, 4,4′-diaminodiphenyl sulphone (DDS), 4,4′-diaminodiphenyl methane (DDM) and biphenyl diamine (BPD) were used as curing agents. The mesomorphic behaviour of DGPP/diamine mixtures and their curing kinetics were monitored by differential scanning calorimetry and hot stage optical polarized microscopy. The thermogravimetric analysis data showed that the LCTs are stable in the range 261-292 °C and afford 36-48% char yield. The limiting oxygen index values are between 35 and 47 proving fire retardance. The mechanical properties of the cured LCTs were characterized by dynamic mechanical analysis.