WU Yuanbo, YUAN Liping, HUANG Zizhi, HU Yunchu, TANG Liandong, LI Hui, HU Jinbo
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In this paper, the effects of heteropolyacids on pyrolysis process of poplar powder and its mechanism were studied by comparing the pyrolysis process and characteristic parameters of heat and smoke release of poplar powder treated with H3PMo12O40(PMA), H3PW12O40(PTA) and H3SiW12O40(TSA). The TG and DTG curves of samples were determined by thermogravimetric analyzer. And the heat release rate(HRR), total heat release(THR), smoke produce release (SPR) and total smoke produce (TSP) were measured by cone calorimetry (CONE). Besides, the FT-IR and Raman spectrometers were used to characterize the residual char. TGA results showed that three heteropolyacids could effectively decrease the initial pyrolysis temperature(Ti), the maximum weight loss temperature(Tmax) and the maximum weight loss rate(Rmax) of poplar wood and increase the char yield at 740 ℃(CR740 ℃). S-wood/PMA had the lowest Tmax and Rmax among all samples, which were decreased by 17.5% and 23.3% than S-wood, respectively. And S-wood/PTA had the highest CR740 ℃, followed by S-wood/TSA. The CONE results showed that parameters of HRR, THR, SPR, TSP, and COY of the heteropolyacid/poplar samples were significantly reduced. S-wood/PMA also had the lowest parameters of heat and smoke release, whose peak heat release rate(PHRR) and THR were decreased by 31.6% and 67.5% and the TSR and TSP were 86.01% and 87.5% lower than those of S-wood, respectively. And FT-IR and Roman spectrums showed that the content of associated O—H and unsaturated CC in the residual char of the heteropolyacid/poplar samples were increased significantly, and ester bonds, MoO3, WO3 and SiO2 formed. Furthermore, AD/AG of heteropolyacid/poplar samples was decreased. Therefore, heteropolyacids catalyze the dehydration of poplar powder into esters and the solidify of poplar powder into carbon by pyrolysis, which effectively slows down the pyrolysis rate and inhibits the pyrolysis process of poplar powder, exhibiting good flame retardancy and excellent smoke suppression effect. And H3PMo12O40 has the best flame retardant and smoke suppression effects on poplar powder among the three heteropolyacids.