Tung oil-based phosphorus-containing polyol as a flame retardant for bamboo

A novel method for preparing a tung oil-based flame retardant polyol (MTTO) is described. An epoxidized tung oil methyl ester was initially prepared using green nontoxic phosphotungstate (Ag 3 O 40 PW 12 ·xH 2 O) as the catalyst. The MTTO was then produced from epoxidized transesterified tung oil (ETOME) using diethyl phosphate and ring-opening. The MTTO molecular structure was analyzed using FTIR, 1 H, 31 P, 13 C NMR, and HR-MS. Both MTTO and MTTO-coated melamine-modified bamboo showed excellent flame retardation, with a UL-94 rating of V-0, increased LOI from 28.3 % to 36.4 % and 38.7 %, and significant reductions in the PHRR and THR of the untreated bamboo of 42.7 % and 50.6 % and 37.5 % and 42.1 %, respectively. MTTO was effective in both the gas and condensed phases, preventing bamboo degradation through the release of non-flammable small molecules and the formation of a cross-linked phosphorus-oxygen network carbon layer. Moreover, the addition of melamine led to the release of more non-flammable gases, expansion of the char layer, and increased density of the nitrogen-phosphorus-oxygen cross-linked network carbon layer during combustion, resulting in reduced PHRR and THR.