The Preparation And Characterization Of Composite Films Based On Wood Auto-Hydrolysate

Lignocellulosic biomass is the most abundant renewable biomass resources,mainly composed of cellulose,hemicelluloses and lignin,including cellulose microfibril as"skeleton",surrounding by the hemicelluloses and lignin crosslinking with three dimensional network structure.The content of hemicelluloses in biomass accounted for 25?35%.For a long time,the utilization of cellulose and lignin research occupied the dominant positions.However,hemicelluloses have not been utilized of high value due to the diversity of species and the complexity of the structure.How to efficiently convert and utilize hemicelluloses,make it become new materials and chemicals to replace petroleum products and reduce environmental pollution have significantly important theoretical and practical significance.In recent years,the pulp and paper enterprises used the hydrothermal treatment technology to degrade in advance and dissolve the cell wall component(wood auto-hydrolysate)in the pulping process,and this technology reduced the energy consumption in the process of pulp and chemicals.However,the utilization of wood auto-hydrolysate became an urgent problem to the pulp and paper enterprises.The study of utilization of wood auto-hydrolysate has realistic and long-term significance to the efficient utilization of lignocellulosic biomass.to the increment of the economic benefits of pulp and paper enterprises,environmental protection.Therefore,wood auto-hydrolysate rich in hemicelluloses was being as raw material andused to form composite films based on wood auto-hydrolysate in this paper.The preparation of' composite films offered the theoretical basis and technical support to the utilization of wood auto-hydrolysate.The conclusions were as follows:(1)The main components of the wood auto-hydrolysate(WAH)are hemicelluloses,xylo-oligosaccharides,monosaccharides and some lignin,and WAH account for 98.35%of dry weight of hydrolyzate.The content of hemicelluloses in WAH is 61.33%,and the content of lignin is 10.51%.The weight average molecular(Mw)is 2300 g/mol,the number average molecular(Mn)is 260 g/mol.The main structure of hemicelluloses is poly-O-acetyl-4-O-methylglucurono-?-D-xylan,Mw is 2720 g/mol.(2)Composite films based on WAH and CS were prepared by WAH and CS through the chemical cross-linking.The surface topography,thermal stability and oxygen permeability of WAH/CS composite films were characterized.The results showed that WAH/CS films had smooth surface,strong tensile properties,tensile strength,good transmittance and the transmittance ranged from 75%to 80%.The oxygen permeation value of composite films was as low as 0.15 cm3·m-2·24h-1·kPa-1.When the volume ratio of WAH and CS was 1:1,composite films had the best mechanical properties,thermal stability and oxygen resistance.(3)On the basis of the preparation and characterization of WAH/CS films,nano-cellulose(NCC)was used as the reinforcing material to prepare the films.WAH/CS/NCC films were prepared by WAH,CS and NCC through the chemical cross-linking.Compared with WAH/CS films,WAH/CS/NCC films had smoother surface,and the tensile properties were significantly enhanced,especially that the elongation at break of the composite films could be as high as 4.7%.The oxygen permeation value of the WAH/CS/NCC films was as low as 3.57 cm3·m-2·24 h-1·kPa-1.Therefore,these great properties of conposite films provide the utilization of the films based on wood auto-hydrolysate in the food packaging field with the theoretical basis and technical support.