Synthesis, flame retardancy, and thermal degradation behaviors of novel organo-phosphorus compounds derived from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)

A series of novel organo-phosphorus compounds was synthesized from 9,10-dihydro-9-oxa-10-phosphaphenanthrene- 10-oxide (DOPO) in an attempt to obtain high phosphorus (P) containing halogen-free flame retardant (FR). The success of synthesis was confirmed by 1H and 31P NMR spectra. The P content of FR varied from 12.95 to 19.22 wt%. Thermal stabilities of synthesized FRs and their flame retardancy for Acrylonitrile-Butadiene- Styrene copolymer (ABS) were investigated by thermal gravimetric analysis (TGA) and the classification of UL-94 V-0 rating, respectively. 27.5-30.0 wt% FR loadings gave the V-0 rating for the ABS/FR mixtures and no fume emission was observed. It was found that the flame retardancy strongly depends on the P content of FR and 5.03-5.30 wt% P is required in the formulation to exhibit self-extinguishing ability when phosphinate or phosphonate FRs are employed. The mode of flame retardancy action is also discussed.