| Phosphate compounds are now widely used as halogen-free flame-retardants in PC/ABS, which was found to generate less toxic gas and smoke than halogen-containing compounds during the fire. 9, 10-dihydro-9-oxa-10-oxide-10-phosphaphen anthrene-10-yl (DOPO) is a notable phosphors containing reaction intermediate. DOPO and its derivatives with the characteristic of fewer toxins and smoke and hard to migration were widely incorporated into polymers to improve polymers'flame retardant (FR) properties and thermal stability.In this paper, two novel phosphorus-containing compounds (DPWDF and DPTS) have been synthesized using DOPO as a raw material. The chemical structure of the intermediates and flame retardants were investigated by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The thermal stability and flame retardancy of the flame retarded PC/ABS were investigated by LOI, TGA, FTIR and SEM. The LOI results show that DPWDF and DPTS improved the LOI value of PC/ABS. when adding 30%, the value of PC/ABS/DPWDF and PC/ABS/DPTS attached to 28% and 27% from 21%, respectively. The TGA results reveled that the FRs decreased the initiate decomposition temperature (IDT) of PC/ABS but enhanced its char residue at high temperature; the active energy of flame retarded PC/ABS was lower than that of PC/ABS before the conversion of 70% while it was higher than that of PC/ABS after the conversion of 70%. FTIR analysis confirmed that the P and Si played a great role in process of char forming. DPWDF changed the degradation molding of PC/ABS by a series reaction of phosphate ester and siloxane and formed the char abundant in P and Si. The char acted as a good barrier to the transfer of heat and combustible gas between the flame zone and the substrate, and thus protected the underlying materials from further burning. SEM investigations revealed that both DPWDF and DPTS flame retarded PC/ABS systems formed the continuous and close outer surface of the char layer.
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