Dongyue Liu,Pengfei Ji,Tianlong Zhang,Jipeng Lv,Yihua Cui
A bi-DOPO type of prepolymer for flame retardancy epoxy resins with intrinsically flame-retardant was successfully synthesized by reacting of 6,6′-((6,6′-dihydroxy-[1,1′-biphenyl]-3,3′-diyl) bis (propane-3,1-diyl)) bis(dibenzo[c,e][1,2] oxaphosphinine 6-oxide) (DOBP) with bisphenol A. The characterization of the cured epoxy resins, such as cone calorimeter, TGA/infrared, Raman and SEM indicated that DOBP with double 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) structure endowed the epoxy resins with excellent flame retardancy, including limiting oxygen index of 40.0%, V-0 rating in UL-94, remarkable smoke suppression and flame inhibition. The quenching effect of gaseous phase and charring effect of condensed phase of phosphaphenanthrene groups in prepolymer together contributed to the improvement on the flame retardant performance of the epoxy resins. In addition, due to the rigid structure of DOBP molecules, the cured d -FREP possessed high glass transition temperature of up to 192.9°C, and the tensile modulus of which was increased about 55% compared with the neat epoxy resins.
Yuan Cao,Xiu-Li Wang,Wen-Qiang Zhang,Xue-Wu Yin,Yue-Quan Shi,Yu-Zhong Wang
A novel reactive phosphorus-containing flame retardant 1,4-phenylene-bis((6-oxido-6H-dibenz[c,e][1,2]-oxaphosphorinyl) methylene) diacrylate (TDCAA-DOPO), with two symmetrical 9,10-dihydro-9-oxa-10-phosphaphena-nthrene-10-oxide structure (bi-DOPO), was synthesized and combined with unsaturated polyester resin (UPR) via cross-linking to prepare flame-retardant UPR (FR-UPR). To make clear both the effects of the bi-DOPO structure and the cross-linking reaction on the thermal stability and flame retardancy of UPR, an additive flame retardant that also owned bi-DOPO structure but without a vinyl bond, 1,4-phenylene-bis((6-oxido-6H-dibenz[c,e][1,2]-oxaphosphorinyl) carbinol) (TDCA-DOPO), was used as a contrast. The results showed that the incorporation of TDCAA-DOPO or TDCA-DOPO into UPR can reduce its peak heat release rate (PHRR) and total heat release (THR), as well as improve the limiting oxygen index (LOI) value. As compared to TDCA-DOPO, the reactive TDCAA-DOPO endowed FR-UPR with enhanced thermal stability, residual char, and glass transition temperature (Tg), which were even higher than those of pure UPR. Besides, their flame-retardant mechanism for UPR had been well investigated.
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