The Research Of Nanocellulose Fiber Raw Material Preparation

Lignocellulose is the most abundant renewable natural resources on earth,which can provide raw materials of preparing energy sources,materials and chemicals for human.Cellulose nanocrystals naturally existed in wood fiber,from which nano-crystalline cellulose extracted has a huge application prospect in fields of biomedical,photoelectric materials,flexible material,so it is of great significance to separate nanocellulose from plant fiber raw materials and produce nanocellulose in large-scale.This thesis mainly selected several plant materials to prepare nanocellulose in different ways,and conducted a new exploration on the preparation method based on the deficiency existing in the traditional method,it provided a theoretical basis for the preparation of nanocellulose using the plant fiber raw material and the improvement of ways to prepare nanocellulose.First of all,the separation of the components of fibre bundle(R14)and parenchyma cell components(P200)were realizedthrough the way of sulfite pretreatment classificationbased on the heterogeneity of palm sheaths,DL-P200 and DL-R14 were obtained by eliminating ligninby chlorite reaction after dispersing in single fiber,then nanocellulose was obtained by pretreating DL-P200 and DL-R14 with TEMPO-oxidation and high pressure homogeneous.The results showed that,the fiber length of R14 nanocellulose was longer than that of P200,the nanocellulose of R14 has more carboxyl content than that of P200 after TEMPO-oxidation,the crystallinity of R14 and P200 had been improved to some extent,while the crystallinity were decreased obviouslyafter high pressure homogeneous,the thermal stability of bothnanocellulose components were less than DL-P200 and DL-R14,andnanocellulose of P200 had abetter thermal stabilitythan that of R14.Secondly,?-cellulose was extracted from the palm sheaths,mango tree and banyan tree and nanocellulose was prepared by hydrolyzing?-cellulose with sulfuric acid.The results indicated that thenanocellulose fiber lengthof palm sheaths,banyan tree and a mango tree were mainly distributed in 60~300nm,70~300nm,and 60~120nmrespectively;the thermal stability of nanocellulose was as follows: mango tree > palm sheath > banyan tree;The chemical structure of nanocellulose and ?-cellulose which were from palm sheaths,mango tree and banyanhad not changed;cellulose II crystal structurehad been retainedin ?-cellulose and nanocellulose,and the crystallinity of nanocellulose increased to some extent than that ?-cellulose.Finally,cellulose of hardwood,cotton linter and softwood had been selected to hydrolyse with sulfuric acid and centrifugal washing.Nanocellulose were obtained through adjusting the pHof cellulose suspensionclose to neutralwith a certain concentration of alkali solution(NaOH)andbeing gotby high pressure homogeneous treatment.The morphology and properties of nanocellulose and enhancement effect of it on the polyvinyl alcohol(PVA)were analyzed.The nanocellulose was got by pretreatment of different time(including 15,30,60,and 90 min)from hardwood,cotton linter and softwood fiber.The results showed thatthe fiber of hardwood,cotton linter and softwood fiber were got in nano-scaled,and the length and width of nanocellulose gradually decreased with the time of acid hydrolysisincreasing;the crystallinity of cotton linter fibers increased with the time of acid hydrolysisincreasing,and the crystallinityreached a maximumof 71.03% when the time of acid hydrolysis was 90 min;the crystallinity ofhardwood and softwood fiber reached maximumsof 71.12% and 72.12%respectively at when acid hydrolyzing time was 60 min;the thermal stability of hardwood,softwood and cotton linterfiberreduced in different degrees after acid hydrolysis;when nanocellulose content in PVA composite membrane was 0.5%,the tensile modulus showed by the composite membrane was higher thanpure PVA membrane by 35% at least.