Preparation And Fibrosis Of Liquefaction Products From Salix Holocellulose

Salix is one of the high quality shrub species that improve the soil environment and control desertification in the desert area of Inner Mongolia.Based on the physiological characteristics that it rejuvenate after mowing,Salix's advantage is huge.Holocellulose refers to the general term for cellulose and hemicellulose,thatis the part ofwood after removing lignin andbenzene-alcohol extractives.Liquefaction technology at ordinary pressure is one of effective ways to utilize biomass resources.Because of differentrawmaterials,chemical functional groups and chemical components of liquefacton products may be different,that may affect the synthesis of subsequent liquefaction products with other compounds.Aiming at the above problems,a series of studies on the preparation and properties of liquefaction products of Salix holocellulose carried out.Based on this,the related research on the preparations of liquefaction products for micro-nanofibers was developed.In this study,Salix holocellulose was extracted,and the liquefaction product is prepared by pressure liquefaction technology at ordinary pressure;first polyurethane is synthesized by liquefaction products and isocyanate and nanofiber of polyurethaneis is prepared by electrospinning;nanofiber of mixture of holocellulose liquefaction products and thermoplastic polyurethane is prepared by electrospinning.The conclusions were summarized as below:(1)Weight-average molecular weight of Salix holocellulose liquefaction product is 7488,and the distribution width is 3.6.Liquefaction products of Salix holocellulose contains protons of alkane,olefin and aromatic which is analyzed by 1H-NMR.Trendof liquefaction residue over time is same as liquefaction of wood powder,but the residue rate is lower than that of wood powderunder the same reaction conditions.It indicates that lignin is a factor that hinders the liquefaction yield.(2)Hydroxylvalueof holocellulose liquefactionproducts is 297.65mgKOH/g and acid value of that is 19.92mgKOH/g.Because of that holocellulose liquefaction product can be polymerized with an isocyanate compound to prepare polyurethane.According to the optimization of the process parameters of polyurethane synthesized from liquefaction products,a suitable polyurethane synthesis process is obtained,which is adding the liquefaction products to MDI,reaction temperature is 80?,and prepolymer reaction time is 2 h.A polymer which has excellent mechanical properties is prepared under the amount of the chain extender is 8.5%.It is concluded that the mass fraction of the synthetic chain extender which can be used as a precursor for the liquefaction products-based polyurethane is 7.0%,7.5%and 8%.(3)According to the response surface methodology,the reaction temperature in the polymerization process of the cellulose liquefaction products and the isocyanate has a very significant effect on the mechanical properties.The amount of chain extender has a significant effect on the mechanical properties,and the reaction time does not affect it significantly.The interaction between reaction temperature andreaction time,interaction between reaction temperature and chain extender,reaction time and the interaction of the chain extender have no significant effect on the mechanical properties of the polyurethane.The ideal process parameters are:reaction temperature 82?,reaction time 2 h,and the amount of chain extender is 8.5%.The predicted parameters of the model were verified under ideal process conditions,and the elongation at break was 169.01%.(4)The holocellulose liquefaction products polyurethane whose chain extenderis 8%is used as the precursor of electrospinning.The spinning solution whose concentration are e 15%and 20%concentration can be electrostatically sprayed under the action of the high voltage electrostatic field.Increasing the spinning voltage,the concentration of solution,and the amount of the chain extender in the design range contribute to the formation of the micro/nano fiber.(5)The micro-nano fiber is prepared by electrospinning of Salixholocellulose liquefaction product with thermoplastic polyurethane.The influence mechanism of the mass fraction of Salixliquefaction products on physicochemical properties of mixed spinning solution and the influence on the microstructure of the composite micro/nanofiber membrane were discussed.With the increase of the mass fraction of holocellulose liquefaction products inmixed spinning solution,the macroscopic and microscopic morphology of the composite micro/nanofiber membrane changed,the fiber diameter increased,the pores between the fibers decreased,and the crystallization state of the fiber membrane changed.The thermal stability of the fiber membrane is reduced and the mechanical properties are lower.