The Construction Of Phase Diagram For Ionic Liquid/Wool Fiber/Coagulator Ternary Systems And Its Application

With the rapid development of economic,people's demand for resources and energy is increasing.As an environment-friendly renewable resource,natural polymers have attracted extensive attention from researchers.Keratin is one of the natural polymers with abundant reserves,wool fiber consists 95 wt.% of keratin,which is an important source of natural keratin and has excellent mechanical and biological properties.However,due to the numerous complex inter-and intra-molecular hydrogen bonds,disulfide bonds and other chemical bonds,wool fiber is insoluble in water and common organic solvents.As an emerging green solvent,ionic liquid(IL)shows outstanding performance in dissolving natural polymers such as wool fiber,cellulose,chitin,etc.due to their tunable structure,non-volatile,thermal stability,as well as high solubility for biopolymer.According to the reports,the current researches on the dissolution of wool fiber by ILs are mainly focused on the solubility properties of wool fiber.The studies on the regeneration properties of wool keratin are still limited.There are three components involved in the regeneration process of wool fiber,and thus the thermodynamic behavior of polymer regeneration can be investigated by the ternary phase diagram.In this study,the linearized cloud point(LCP)correlation and ternary phase diagram of IL/wool fiber/coagulator system were constructed by the turbidity method.The effects of coagulator types,coagulation temperatures,and structures of ILs on the properties of wool keratin regeneration were investigated systematically.The interaction between IL,wool fiber and coagulator at different temperatures was predicted by the Conductor-like Screening Model for Real Solvents(COSMO-RS).In addition,the optimized IL of 1-ethyl-3-methylimidazole diethyl phosphate([Emim]Dep)was used to dissolve wool fiber/wood pulp cellulose to prepare composite fiber,and the influence of wool fiber/wood pulp cellulose ratio on the mechanical properties and thermal stability of composite fibers were systematically studied.The research results are as follows:(1)The construction of the IL/wool fiber/coagulator ternary phase diagram.The LCP correlation at the low mass fraction of wool fiber of IL/wool fiber/coagulator can be generated from the experimental cloud point combined with the Boom empirical equation.And the phase diagram at the whole mass fraction of IL/wool fiber/coagulator was extrapolated by the LCP correlation.The effects of coagulator types,coagulation temperatures,and the structures of ILs on the properties of wool keratin regeneration capacity were investigated systematically by LCP correlation and ternary phase diagram.The regenerated wool keratin was obtained using [Emim]Dep as the solvent with the coagulation temperature of 25 ?.In different coagulator systems,the order of wool keratin regeneration capacity is water > ethanol > iso-propanol.The regenerated wool keratin was obtained using [Emim]Dep as the solvent,and water as the coagulator.In different coagulation temperature systems,as the coagulation temperature increased,the regeneration capacity of wool keratin gradually decreased.The regenerated wool keratin was obtained using water as the coagulator with the coagulation temperature of 25 ?.In different IL structure systems,the order of wool keratin regeneration capacity is [Emim]Dep > 1-ethyl-1,5-diazabicyclo[4.3.0]non-5-enium diethylphosphate([DBNE]Dep)> 1,5-diazabicyclo[4.3.0]non-5-enium acetate([DBNH]OAc).(2)The interaction of [Emim]Dep,wool fiber and coagulator.COSMO-RS was used to predict the interaction of [Emim]Dep,oxidized glutathione(wool fiber model,GSSG)and coagulator(water,ethanol and iso-propanol)with the coagulation temperature of 25,40,60 ?.Among them,the interaction of [Emim]Dep,GSSG and water is greater than that of ethanol and iso-propanol,and as the coagulation temperature increases,the interaction of [Emim]Dep,GSSG and water gradually decreases.(3)The effects of regeneration conditions on the properties of regenerated wool keratin.The regenerated wool keratin was obtained using [Emim]Dep as the solvent,and water(25,40,60 ?),ethanol(25 ?)and iso-propanol(25 ?)as the coagulator.The crystallinity and ?-helix structure content of regenerated wool keratin with water as the coagulator are higher than that of ethanol and iso-propanol,and as the coagulation temperature increased,the crystallinity and ?-helix structure content of regenerated wool keratin gradually decreased.The crystallinity and ?-helix structure content of regenerated wool keratin using water as the coagulator with the coagulation temperature of 25 ? are 22.5% and 84.1%,respectively.(4)The effects of wool fiber/wood pulp cellulose radio on the performance of wool fiber/wood pulp cellulose composite fiber.The composite fiber was prepared using [Emim]Dep as the solvent with different wool fiber/wood pulp cellulose radio.When the wool fiber/wood pulp cellulose radio is 1 : 9,the mechanical properties and thermal stability of composite fiber are the best,i.e.,523 MPa and 295 ?,respectively.