Extraction Of Rice Straw Fiber And Preparation And Application Of Nanowhiskers

Cellulose is formed by glucopyranoses ringing with each other by D-beta(1-4)linear polymer-D-glycosidic bond with chair conformation and it is the main component of the cell wall of plant that generally exists in the nature.The annual output of cellulose is about 1.5 × 1012 tons.How to use this natural resource to meet our growing demand for environmentally friendly and biocompatible products has become a hot issue.Straws,trees and other plant waste are all including cellulose,so they can be regard as ideal raw-materials to extract cellulose nanowhiskers.In this paper,rice straw was used as raw material to prepare cellulose nanowhiskers.Alkaline solution system was used for chemical purification treatment,firstly;and then TEMPO-Na Cl O-Na Br(2,2,6,6,four-1-oxyl-nitrogen oxide sodium bromide and sodium hypochlorite)system was facilitated to prepare cellulose nanowhiskers.The corresponding processing parameters were all optimized to obtain cellulose nanowhiskers with uniform size and high yield.And finally,the cellulose nanowhiskers obtained in this paper were used to improve the ultraviolet resistance of cotton fabric.The main research contents of this paper can be divided into four sections:(1)Characterization of structure and properties of rice straw.The chemical composition,moisture regain,infrared spectrum,surface and cross-section morphology and crystallinity of rice straw were all analyzed.The following results can be obtained: the moisture regain of rice straw is7.61%;rice straw mainly contains lignin,hemicellulose,cellulose,water soluble pectin,fat,and wax,among which the content of hemicellulose and lignin are both higher than that of cellulose;there are closed holes in the cross-section of rice straw,and some of the holes are continuous;There are spherical particles distributing on the walls of some large holes;the longitudinal surface of rice straw is uneven,and distributed with spherical particles in different sizes;and the crystallinity of rice straw is 29.76%.(2)The optimization on processing paramters and characterization of rice straw fiber.The effects of pretreatment and purification process,including chemical reagent concentration,reaction time,solid-liquid ratio and temperature,on the weight loss rate of rice straw were discussed to obtain the optimized processing parameters.In addition,the characteristics of the rice straw fibers,such as chemical composition analysis,morphology,infrared spectrum test and crystallinity test,were analyzed.The results show that: the cellulose content of rice straw fiber is higher than that of rice straw,while the content of hemicelluloses and lignin decreased significantly;the spherical particles in the surface of rice straw are removed,and those particles in large holes are also significantly reduced;the fiber surface becomes relatively smooth;The degree of crystallinity is higher than that of rice straw.(3)Preparation of cellulose nanowhiskers of rice straw.The cellulose nanowhiskers were prepared with TEMPO-Na Cl O-Na Br catalytic oxidation system.The scanning electron microscopy,infrared spectroscopy,transmission electron microscopy,crystallinity,yield and thermogravimetric analysis were all used to analyze the characteristics of nanowhiskers.Then the following conclusions can be obtained: the cellulose nanowhiskers have average diameter of10~25nm and average length of 200~400nm;they will weave into a multi-layer mesh distributing with pores in different sizes after freeze dried;X-ray spectrum shows that the nanowhisker have higher crystallinity than rice straw and fiber,i.e.40.71%;the yield of nanowhiskers is about 80%;the thermal decomposition temperature is 320?.(4)The application of rice straw cellulose nanowhiskers in the anti ultraviolet function of cotton fabric.The nanowhiskers and chitosan were uniformly mixed with the catalysis of tannic acid to prepare finishing solution.The effects of nanowhiskers content on the breaking strength,infrared spectrum,contact angle,washing resistance and ultraviolet resistance of cotton fabric were analyzed.The breaking strength of cotton fabric with the addition of nanowhiskers is greatly improved;the spectrum bands have no obvious changes,indicating that the nanowhiskers were not changed by TEMPO oxidation system;with the increase of nanowhiskers content,the hygroscopicity,washing resistance and anti ultraviolet performance of cotton fabric all increase first and then decrease;and the content of nanowhisker is optimized as 0.5%.