| China has the richest straw resources in the world,with the annual output amounting to more than 700 million tons,among which corn straws account for 36.7%,rice straws account for 27.5%and wheat straws account for 15.2%.AS calculated,the amount of rice straw extracted from 200 million tons of rice straws can reach 100 million tons.The number of the mulberry branches that are cut down is also astonishing.In 2006,the output of mulberry silkworm cocoon in our country amounts to 738,000 tons,accounting for 70% of that of the world.And the output of the raw silk is 93,000 tons,among which the export volume occupies the leading position in the world for it accounts for more than 70%of that of the world.According to calculation,740,000 tons of silkworm cocoon per year needs about 10 million mu of mulberry fields.In order to maintain the mulberry trees and the soil nutrient,the mulberry trees need to be cut down in summer and trimmed in winter.It is estimated that about 4 tons of mulberry branches will be cut down in the mulberry field per mu.About 17%of mulberry branches are the mulberry cortices and about 30%are mulberry cortex fibers.Thus the waste mulberry branches per mu can produce about 200 kilograms of the mulberry fibers and the total yield can amount to about 2 million tons, which is about 3 times as much as that of 2006.From this,we can fred that there is big space for the exploitation of rice straw fibers and mulberry cortex fibers.And this thesis researches and discusses the methods of extracting nonwoven fiber material from agricultural waste material——rice straws and mulberry cortices.The extraction of rice straw fibers combines chemical methods with physical methods. Under certain temperature and time,the alkali of low density will dissolve the lignin of the fiber cells of rice straws,make the polysaccharide substances that stick to the fiber cells loose and fall off and make fiber cells split into threads.And the even stirs provide the force of dispersion for the fiber cells and strengthen the effect of Na~+ of low density.Na~+ of low density can not dissolve all the lignin and polysaccharide substances.For instance, lignin of the non-hydroxybenzene type ofα—aryl aether bond and lignin of the hydroxybenzene type ofβ—aryl aether bond are very difficult to be dissolved by solution of low density.So parts of lignin and polysaccharide substances still stick to the fiber cells, thus making the fiber length can be measured by the unit of centimeter.The conclusions are shown as the following:the mass ratio of rice straw to NaOH is 1 to 0.6;the ratio of rice straw to solution(g:ml) is 1 to 30;the temperature is set under 90℃;the rotational speed of the rotor is 720r/min and is evenly stirred when heated and the optimum result of the experiment can be reached after 120 minutes:the average length office straw fibers is 10.3mm and the average width is 19.31μm;the cellulose content of fibers is 74.85%,the content of ash is 2.21%,the ratio of fibrillating is 25.88%and the ratio of the tow that is not dispersed is 0.5%.The extraction of mulberry fiber is such a method:the mulberry cortex is dipped in under open wide,airproof,indoor and outdoor circumstances with different water.After fermentation,the cuticle and phloem of mulberry cortices separate from each other.And then mulberry fibers of phloem disperse into fiber singles which provide a cheap,fast, natural extraction way for mulberry fibers to be used for agriculture soil-film extracted from nonwoven fabrics.During fermentation,air temperature,humidity,water temperature, pH,the growth of organisms in water and changes of mulberry cortex fibers are all recorded in detail.The composition and content of mulberry cortices after extraction are tested and discussed and the feasibility of wet-laid nonwoven fabric of fiber after fibrillating is predicted.The thesis,based on the experiment,draws the conclusion that mulberry cortices,when dipped in pond water or running water indoors under open wide circumstance for 20 or 25 days will reach the optimal fiber single ratio.The temperature of the experiment is between 25℃and 32℃.The average length of mulberry cortex fibers that is extracted is 23.2mm and the width is 18.9μm;the content of cellulose of the fibers is 73.92%;the regain is 7.63%and the extraction of Benzene alcohol is 2.42%.This thesis adopts different methods to extract fibers from different agricultural waste for nonwoven material.The two kinds of fibers extracted have some differences in characteristics,quality,composition and state.Composed with mulberry cortex fibers,rice straw fibers are strong and short.The cellulose content of rice straw fibers,however,is similar to that of the mulberry cortices.From the picture of scanning electronic mirror,we can directly find that rice straw fibers and the mulberry cortices are similar in surface structure.And if we compare the pictures of trice straw fibers and the mulberry cortex fibers with the picture of scanning electronic mirror of cotton fibers,we will find the three kinds of fibers are all similar in surface structure.The newborn layer,with spiral-shaped wrinkles on the surface,is the outermost layer of the fibers and is one of the characteristics of cellulose fibers.By further analyzing the infrared spectrum,the conclusion is drawn that rice straw fibers,the mulberry cortex fibers and cotton fibers,all very similar in microstructure and composition,are cellulose fibers.The main groups contained in the fibers are about the same,so the general shapes of the spectrum picture are close and the spectrum bands of absorption crest created by the vibration of each chemical bond have no sharp differences.The difference lies in the fact that the amounts of the content of each group influence the intensity of absorption of infrared.The two kinds of fibers can be blended according to their characteristics.We can maximize favorable factors and minimize unfavorable ones to produce products of different standards for different requirements. |
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