The Study Of Polysaccharide Flame Retardant Materials And Its Application In Reconstituted Tobacco Sheet

Intumescent flame retardant(IFR)technology is a newly flame retardant technology developed in the 1990s.Biodegradable polysaccharides have abundant sources and can replace traditional(IFR)carbon sources,therefore it has become a research hotspot in FR field recently.Due to the advantages of low cost,and ability to decrease content of tar,reconstituted tobacco sheet(RTS)has been widely applied in tobacco industry.The pyrolysis and combustion process of RTS have a significant impact on the amounts of harmful chemicals in mainstream smoke.In this thesis,based on above analysis,polysaccharides IFR materials were used to obtain modified RTS.The effects of IFR on the pyrolysis,combustion properties and products of RTS were studied through a series of methods.The main works of this thesis are as following:1.Three IFR modified RTS were produced by papermaking process,with ammonium polyphosphate(APP)as acid,gas source and starch(ST),distarch phosphate(DSP)and hydroxypropyl distarch phosphate(HPDSP)as carbon source.The effects of three carbon forming agents on FR performance were compared and the results showed that starch-based FR materials could form char with better thermal stability in the pyrolysis stage of cellulose and hemicellulose.The oxidation decomposition of char moved to high temperature range and the rate were decreased,so as to suppress combustion and pyrolysis of RTS.Meanwhile,the release of carbonyl compounds was inhibited and the cross-linked phosphate groups in modified ST could further improve the thermal stability of char and flame retardancy of FR.2.Model-free function and model-fitting methods were used to analyze thermal kinetics on the starch-based FR modified RTS.The activation energy(E?)calculated by the FWO and KAS methods showed that when the conversion rate a was in the stage of 0.10?0.65(150?300?),the E? of RTS presented increases-stable-increase trend.Starch-based FR could significantly reduce the E? at this stage.Among them,the APP-DSP made the smallest Ea value in the entire range,while APP-ST mainly reduced the Ea with a range of 0.10?0.40.The fitting results of the mechanism functions by Coats-Redfern method showed that the initial degradation of reducing sugars,pyrolysis of hemicellulose conformed to the diffusion model,the pyrolysis of cellulose and char conformed to the second-order chemical reaction model,and decomposition of inorganic salts agreed to Nucleation and Growth model.The more stable char formation of starch-based FR at 220?390? was mainly achieved by reducing the activation energy of hemicellulose.At the same time,compared with the control,the pyrolysis activation energy of char increased,reflecting its better thermal stability.3.A ternary IFR coating was prepared by layer-by-layer self-assembly(LBL)method to form on the RTS surface,with APP as the acid,gas source,chitosan(CS)as the carbon source,and potassium citrate(PC)as the synergist and its flame retardancy was studied.The results showed that:APP-CS coating could decompose in the surface of RTS earlier,forming micro-intumescent char layer.While PC could react with intermediates of polysaccharides pyrolysis,forming potassium-carbon complex,which cooperated with char to enhance the flame retardancy of the coating.The more stable potassium-carbon complex inhibited the further reaction of saccharide intermediates,decreasing the amounts of aldehydes.Subsequently it decomposed to produce more ketones.The synergistic effect of PC and APP-CS further inhibited the pyrolysis and combustion process of RTS,which not only reduced the peak heat release rate(PHRR)and total heat release(THR)by 18.3%,20.0%,the maximum temperature of the cigarette burning cone(100?)and the amounts of formaldehyde(67.3%),acrolein(16.4%)in mainstream smoke were also reduced.