| Nowadays,the global plastic waste is increasing rapidly,which has caused serious environmental pollution.It not only consumes the increasingly exhausted oil resources,but also causes great losses to the global economy.In addition,because plastic products can't be completely decomposed,but converted into countless smaller plastic particles,which has caused serious damage to the ecosystem.In recent years,researchers have been trying to find more environmentally friendly bio based materials instead of plastic products to solve the problems of lack of petroleum resources,environmental pollution and ecological hazards.Cellulose is the most abundant renewable natural polymer in nature.Due to its low cost,biodegradability and environmental friendliness,it has shown unique advantages in the sustainable development of resources,energy and environmental protection.However,cellulose is insoluble in water and most common solvents due to the existence of a large number of hydrogen bonds within and between molecules.Cellulose membrane used in packaging materials,membrane separation and agricultural membrane also have poor transparency and mechanical properties,and the preparation process is complex.Therefore,it is the best choice to improve the solubility of cellulose and prepare cellulose membrane with high transparency and good mechanical properties by simple technology.Cellulose carbamate(CC)was synthesized from alkali cellulose and urea by solid-liquid phase method with N,N-dimethylacetamide(DMAc).Then CC was dissolved in cuprammonia solution,and cellulose membrane was prepared by regeneration.In order to further improve its toughness,glycerol was used as plasticizer.The structure and properties of CC,its regenerated membrane and plasticized membrane were studied.The results of FTIR,XRD and TG showed that CC was successfully prepared from alkali cellulose,and it still maintained the good thermal stability of cellulose.The solubility of CC in cuprammonia solution shows that the solubility of cellulose in cuprammonia solution is greatly improved with the mass fraction of CC up to 17%.The effects of coagulation conditions on the structure and properties of regenerated cellulose membrane were investigated by orthogonal design.The results show that the optimal coagulation conditions are 160 g concentrated sulfuric acid and 280 g sodium sulfate when CC is 15 wt%.At this time,the regenerated cellulose membrane is easier to form,the transmittance is 95.50%,the breaking strength is 106.23 MPa,the elongation at break is 23.86%,the transmittance is high,and the mechanical properties are excellent.The heat preservation and moisture retention performance is very good,and the effect is basically close to the conventional polyethylene membrane.FTIR,XRD,TG analysis showed that the regenerated cellulose membrane had good hydrophilicity,retained the original stable crystal structure and good thermal stability of cellulose.Scanning electron microscopy(SEM)showed that the surface morphology of regenerated cellulose membrane was dense,and there were no macropores,and there were regular pores in the cross-section.The effect of glycerol concentration on the mechanical properties and transmittance of the membrane was studied.The optimum concentration of glycerol for plasticizing was 6%.At the same time,the elongation at break can also be greatly improved,and the transmittance,heat preservation and moisture retention performance are good,and the effect is basically close to the regenerated cellulose membrane.FTIR and TG analysis showed that the plasticized cellulose membrane maintained good thermal stability.Glycerol plasticized membrane is green and environmental friendly,with high strength,good toughness and biodegradability.It has a good application prospect in the fields of agriculture,packaging and food preservation... |
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