Corncob Hemicelluloses With Hot Water Extraction Method And Production Of Films Prepared From Agricultural And Forestry Biomass Hemicelluloses

Hemicelluloses, accounting for on average up to50%of the biomass of annual andperennial plants, have emerged as an immense, mutifunctional renewable resource ofbiopolymers. The cellulose and lignin of the agriculture and forestry biomass resourceshave been run the operations at scale, but hemicelluloses have not been reasonableapplication. So it is of great significance by extracting hemicelluloses in agriculture andforestry biomass and turning out high value products according to its characteristics.Firstly, the agricultural waste corncob which contains rich hemicelluloses wasselected as the research object to extract the hemicelluloses. The process of hot waterpre-extraction at different temperatures, time and liquor ratios were investigated,According to the single factor analysis and response surface analysis, the optimizedconditions of hot-water pre-extraction were: maximum temperature170.04℃,extraction time31.40min and liquor ratio14.19:1, and the actual hemicelluloses yield is50.03%.In the part of high value-added application of hemicelluloses in the field of filmsmaking, two aspects were divided:(1) Improve the performance of hemicellulose films by adding reinforcing agent.The possibility of using hard wood hemicellulose hydrolysate from dissolving pulp millfor preparation of hemicellulose films in combination with corn starch, sodiumcarboxymethylcellulose（CMC）and polyvinyl alcoho（lPVA）was investigated, and theinfluence of different additives on the film mechanical properties was also discussed.Results show that PVA has advantages than the other two additives, therefore the PVAwas selected as the optimization additives for hemicellulose films. Then the amounts ofPVA on the influence of film mechanical properties were evaluated. The fims was verysoft and of lower Elasticity Modulus when the ratio of PVA to hemicelluloses wasunder20%, however the strength properties and Elasticity Modulus of films increasedwith increasing amounts of PVA. Taking the cost and practicability into account, theoptimized ratio of PVA to hemicelluloses determined to be30%. Finally, the preparedfilms was briefly characterized by means of SEM, It was shown that the films had asmooth、uniform and continuous surface and dense cross section without the phaseseparation. Besides, The FT-IR spectroscopy showed that all components of films hadgood compatibility and no change between each other. They were crosslinking with physical form and had no chemical reaction in the films. Similarly，the corncobhemicelluloses has a potential for production of films. To add30%PVA to thehemicelluloses, the components can form a continuous semitransparent films with adark yellow color. The films had a smooth、uniform and continuous surface and densecross section without the phase separation. Besides, The Mechanical Properties andthermal Characteristics showed that the films had a TS of4.6MPa, E-value of6.4%.(2) Improve the performance of hemicellulose films by preparing carboxymethylmodified hemicelluloses. The material was alkaline hemicelluloses liquor from chemicalfibres factory. Modified the hemicelluloses by using for reference the preparation ofCMC. In combination with different amount of sorbitol, the carboxymethyl modifiedhemicelluloses can form different films. And3.4%was selected the optimizedconcentration of sorbitol, The mechanical properties and TG analysis showed that thefilms had a TS of4.6MPa, E-value of6.4%, and a nice thermally stable than woodhemicellulose films added reinforcing agent. SEM shown that the films had a smooth、uniform surface and dense cross section. All the data can see that macromolecular chainof modified hemicelluloses have strong interaction with sorbitol, and they constitute athree-dimensional reticular structure through hydrogen bonding, therefore the films haveexcellent film-forming property.