Investigation on the heat resistance mechanism of phosphate containing formulations using the pyrolysis GC-MS system

Abstract

Aiming to probe into the heat resistance mechanism of triallyl phosphate (TAP) modified polyolefin formulation, several phosphate containing model polymers or compounds were designed and their thermal decomposition behavior were analyzed using the powerful pyrolysis GC-MS system. For the TAP homopolymer (PTAP), ethylene vinyl alcohol copolymer (EVOH) crosslinked with phosphorus oxychloride (POCl3), and ethylene propylene diene monomer (EPDM) or polyolefin elastomers (POE) crosslinked with TAP, the reductants like phosphine (PH3) and phosphorus (P4) can be discriminated in the decomposed fragments. However, for the phosphate containing compounds with low molecular weight, such as tri-butyl phosphate (TBP) and tri-octadecyl phosphate (TOP), no any signals attributed to the reductants can be detected. According to the pyrolysis GC-MS results, it can be concluded that the degradation of phosphate containing model polymers or compounds occurred on P–O or C–O bonds. For the crosslinked model polymers, the phosphate groups were immobilized into the 3D network and the reductive PH3 and P4 can be finally generated by cleaving on P–O bond. However, for the small molecular weight phosphate compounds, the fractions after degradation were readily evaporated out from the mixture, which terminated the further reduction of phosphate and the cleaving on CO was dominant. The observation in current work suggested that the restriction or immobilization of phosphate groups played an important role on the generation of reductive PH3 or P4.