Kinetics of thermal degradation of intumescent flame-retardant spirophosphates

The thermal degradation behaviour of various spirophosphates synthesized using SDP (phenol), SDOC (o-cresol), SDMC (m-cresol), SDPC (p-cresol), SDDMP (2,4-dimethylphenol) and SDTMP (2,4,6-trimethylphenol) with 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro-[5,5]-undecane-3,9-dioxide (SDCDP) are investigated using thermogravimetric analyzer. The spirophosphates show multistage degradations in the temperature range 180–550°C. The second stage of degradation is more prominent and the substituent effect is clearly reflected at this stage of degradation. The compound SDP showed superior performance since it has the greatest char yield value (44%) and LOI value (27%). The model free kinetic methods of Flynn-Wall-Ozawa and Vyazovkin methods are used to calculate the apparent energy of activation for the thermal degradation (Ea-D) of these spirophosphates. The material SDTMP showed the highest Ea-D values.