Preparation And Characterization Of Cellulose/Polylactic Acid Composites

In recent years,the problem of environmental pollution has seriously affected our health and life,especially the haze problem,which is that we have been the focus of attention.One of the main causes of this problem is the burning of large amounts of agricultural waste in farmland,which not only exacerbates environmental problems,but also wastes natural resources.However,there is a lot of wheat straw fiber in the wheat straw,the natural renewable resources,which can be transformed into wheat straw fiber by modifying.By doing this,the wheat straw fiber has been widely used in industry,to enhance the utilization value of wheat straw resources.In recent years,the problem of white pollution has also been the difficulty of environmental problems.For the non-degradable problem of plastics,many scholars proposed that biodegradable polylactic acid as raw materials were used for the preparation of plastic,however,with polylactic acid as raw materials,production costs are too high and its tear resistance is relatively poor.From what have been discussed above,in this thesis maleic anhydride esterified wheat straw fiber was prepared by wheat straw fiber,industrial waste by extracting lignin from aqueous alkali soaking wheat straw,as the material,concentrated sulfuric acid as a catalyst and maleic anhydride as the esterifying agent via solvothermal method.Esterified as well as unesterified wheat straw fiber reinforced polylactic acid biocomposites were fabricated using the mechanical method of internal mixer,for enhancing biocomposites' mechanical and thermal properties.Reducing the production costs of derivatives is conducive to the wide range of polylactic acid materials and the comprehensive utilization of waste resources.It is of great necessary for environmental protection and recycling economy.This thesis deals with the following research results after a systematic study.1.The aim of this research work was to successfully synthesize of esterified wheat straw fiber by the esterification reaction of wheat straw fiber and maleic anhydride via solvothermal method.At 140 oC of reaction temperature,4h of reaction time,1g wheat straw fiber/10 g MA and 0.12 m L H2SO4,esterification reaction tended to equilibrium,and degree of substitution(DS)maximum is 1.9.The products were analyzed by FT-IR and SEM.It was found that the esterification reaction occurred and the length of the cellulose was reduced,improving its dispersity.2.The further research work was to investigate esterified wheat straw fiber potential as filler for the fabrication of PLA biocomposites.The results shows that the flexural strength of the composites added with 5wt% fiber was the highest,which was about 26%-28% higher than that of the former.At the same time,the bending modulus was also greatly improved.Furthermore the composites with 5wt% esterified cellulose had better properties,which could be improved by 4% compared with pure PLA,and the elongation at break and tensile modulus were also improved.3.In this research work,wheat straw fiber was successfully oxidized and shortened its macromolecular chains using sodium hypochlorite.At 50 oC of reaction temperature,3h of reaction time,p H=9 and 40 m L sodium hypochlorite,oxidation reaction tended to equilibrium,and crystallinity maximum was 61.7%.After SEM analysis of the diagram can know that the wheat straw fiber macromolecular chain was broken and the appearance of color had been transformed from brown to white.The hydrophobicity of the obtained sample is improved and the contact angle is 42 o by the contact angle test.