Dissolution Of Cellulose By Ionic Liquid And Its Application In Flame Retardant Materials

Cellulose is a natural polymer compound that is renewable,easily degradable,and has the most abundant reserves.However,due to its high aggregation structure,it is difficult to dissolve in common solvents.Therefore,the development of a solvent for dissolving cellulose has become one of the keys to solve the problem of efficient utilization of cellulose.At the same time,cellulose is flammable,burns fast,generates high heat,and generates toxic gases,which seriously affects people's lives and property safety.Therefore,it is very important to study the flame retardant modification of cellulose.Ionic liquid is known as the "green solvent",with low vapor pressure,high stability,excellent solubility and other characteristics,is a green solvent easy to separate,can be used as a good solvent system of cellulose,cellulose for the wide application of the feasibility.In this paper,two kinds of chlorinated 1-(carbamoymethyl)-3-vinyl imidazolium ionic liquid[CmVIM]Cl and chlorinated 1-(4-hydroxybutyl)-3-vinylimidazole ionic liquid[HbVIM]Cl were synthesized Ionic liquid,the solubility of two ionic liquids and tetrabutylammonium chloride(TBAC)mixed solvent system to microcrystalline cellulose(MCC)was analyzed,and the regenerated cellulose and melamine phosphate(MP),ammonium polyphosphate(APP)and nano-silica(SiO2)compounded to prepare flame retardant cellulose composite materials,and analyzed the effects of different flame retardants on their flame retardant properties.The research content and results are as follows:(1)Using 1-vinylimidazole and 2-chloroacetamide as raw materials,[CmVIM]Cl was synthesized by one-step method.The structure and stability of the product were analyzed and characterized by FT-IR,'H NMR,13C NMR and TGA,which showed that the synthesized product was the expected product,and[CmVIM]Cl had good thermal stability.The optimal synthesis process optimized by orthogonal experiments is:n(1-vinylimidazole):n(chloroacetamide)=1:1.2,reaction temperature 85?,n(chloroacetamide):n(TEA)=1:0.5,reaction time 13 h,yield 85.8%.The dissolution experiment results show that at 25 min,the dissolution rate of[CmVIM]Cl/TBAC to MCC can reach 6.3%.At this time,the crystallinity of the regenerated MCC decreases from 74.0%to 46.4%,and the degree of polymerization drops to 505.There was no derivatization reaction before and after the dissolution of MCC,only the hydrogen bond was broken,which resulted in the decrease of thermal decomposition temperature.The crystal structure of MCC changed from cellulose ? to cellulose ? crystal form,which ehhanced the accessibility and reactivity of MCC and provided the possibility of further modification and application of cellulose.(2)Using 1-vinylimidazole and 4-chloro-1-butanol as raw materials,[HbVIM]Cl was synthesized by microwave heating one-step method.The structure and stability of the product were characterized by FT-IR,1H NMR and TGA,which showed that the product had the expected structure and its initial decomposition temperature was 120.8?,which was worse than the thermal stability of[CmVIM]Cl.The optimal synthesis process by response surface method was as follows:microwave power 330 W,n(4-chloro-1-butanol):n(1-vinylimidazole)=1.06:1,reaction temperature 73?,reaction time 90 min,maximum yield 73.62%.The dissolution experiment and FT-IR,XRD,TGA and SEM were used to analyze and characterize the structure,crystallinity,thermal stability and morphology of cellulose before and after regeneration.It showed that the dissolution rate of MCC could reach 5.5%at 45 min.The crystal form of MCC changed from cellulose ? to cellulose ?,its crystallinity decreased,and no derivatization reaction occurred during the dissolution.The surface area of MCC obtained by solvent treatment is uneven,which increases the contact area of cellulose.(3)The fiber flame retardant material was prepared by MP/APP/nano-SiO2 and recycled MCC.The experimental results showed that the synergistic effect of the three flame retardants was better than that of the single flame retardant,and the limiting oxygen index exceeded 28%.When m(MP):m(APP):m(SiO2)=1:2:2,the flame-retardant effect is the best,the limit oxygen index value is 33.5%,the vertical combustion grade is V-0,then the weight loss zone of the flame-retardant fiber composite material rises from 318.2??392.4? to 417.6??434.2?.SEM research shows that MP/APP/nano-SiO2 adheres to the surface of MCC,forming a dense insulating layer on the surface,thus playing a flame retardant effect.By modifying the flame retardant of cellulose,the limitation of cellulose flammability was broken and the application field of cellulose was broadened.