The Study On Properties Of Cotton Stalk Fibre And Composites

In this strudy, Cotton stalk fibre were used to prepare the cotton stalk/plastic compositesby hot pressing. In order to provide the opitimus information on Cotton stalk fiber tocommercial market, the effects of stalk fiber compounding factors on the properties of thecomposites were evaluated and compared to the basic data.The microscopic structure of Cotton stalk was observed and analyzed by opticalmicroscope. Some approaches of quantitative anatomy, micrological image analysis were usedto explore the anatomical properties of Cotton stalk. Chemical components were measuredaccording to the National Standards. The fiber morphology, mechanical strength,cross-sectional area and the crystallinity of single Cotton stalk bast fiber were investigated byfiber length analyzer, fiber tensile tester, laser confocal microscope and X-ray diffraction.Morphological structures, dimensions and mechanical properties of fibre in Cotton stalk bastand xylem were investigated using optical microscope and fiber tensile strength tester afterthey were disposed by rub silk process. Different kinds of recycled plastic were compoundedwith verious types of Cotton stalk fibre. The Cotton stalk/plastic composites were preparedusing hot pressing. The effects of different fibre and plastic on the properties of the compositeswere evaluated.The results show that:⑴The structure of Cotton stalks was similar to hard wood. The shape of stalk fiber wasgood quality. The values of fiber geometric dimensions including mean of fiber length, ratio offiber length to width and ratio of fiber were742.70μm,37.66and77.28%, respectively. Cottonstalk bast fiber length was approximately two times the xylem fiber. The vessel and fiberproportion in different parts of Cotton stalk was significant different. In Cotton stalk, therewere higher vessel ratio and lower fiber ratio in Cotton stalk base, howerer, ray ratio in eachpart of Cotton stalk changed little. The chemical components of the bast and xylem of Cotton stalk were very different. Comparing with the xylem, the bast had more extractive contents,holocellulose, and ash contents. But pentosan content was lower.⑵The average ranges of length and width of cotton stalk bast fiber were1484.43±753.78μm and18.9±6.61μm respectively, with65.75aspect ratio. The Cotton stalkbast fiber is almost solid or extremely little hollow with the shape of diamond or circle. Thestress-strain curve was highly linear with no obvious yield stage. During stretching the elasticdeformation of Cotton stalk bast fiber was covered from0to7%. The mean values of its tensilestrength, elastic modulus and elongation mean were0.89GPa,13.66GPa,6.32%. Those resultswhich the single bast fiber of Cotton stalk has tiny elastic modulus indicates that it is relativelybig elongation at break and has good flexibility. Thought, the crystallinity of Cotton stalk bastwas less than chinese fir, masson pine, paulownia and other plants, it was quite siminlar withxylem. The resrult that Cotton stalk owned low crystallinity suggests there is much moreamorphous area in cotton stalk fiber, in which absorbs water or other chemicals more easily.⑶The shape of cross-section fibre was not regular circle, shown a polygonal or irregular.The averages length value of bast fibre was25.12mm, whose was two times of xylem fibre(13.57mm). The averages width value of bast fibre was201.90μm, which was slightly smallerthan the width of xylem fibre beam (253.36μm). The aspect ratio of bast fibre was about twotimes of xylem. The cross-sectional area of fibre in Cotton stalk bast was42119.69μm2, lowerthan the area in xylem (69249.16μm2). Tensile strength and elastic modulus of fibre in bastand xylem were60.73MPa,2.10GPa and42.58MPa,1.33GPa respectively. Because of thebigger elongation at break, fibre in bast owned a better flexibility. The mechanical property ofCotton stalk was poorer than other plant fibre. The mechanical property of fibre in bast waslower than single Cotton stalk fiber. The tensile strength, elastic modulus and elongation offibre had the decreasing trend with the cross-sectional area increaseing. The interfacial shearstrength of xylem fibre in polyethylene matrix was5.05MPa, and the interfacial shear strengthof bast fibre in polyethylene matrix was just3.96MPa.⑷In order to solve the water resistance problem of Cotton stalk, Cotton stalk fibrecomposite with polyethylene was prepared with the Cotton stalk/plastic composites by hot pressing. The results shows: bending strength, elastic modulus,24h water thickness swellingrate and internal bond strength of xylem fibre composites are higher than those of the bast fibrecomposites. The bending strength and elastic modulus of polypropylene composites was higherthan that of polyethylene composites. Among them, recycled plastic composites is minimum.The24h absorbent thickness swelling rate of composites using recycled plastic wassignificantly greater than that of the polyethylene and polypropylene composites, the internalbond strength of composites using polypropylene is higher than that of recycled plasticscomposites. The properties of the composite uncovered with poplar veneer exceed thedemanded values of the particleboard for load-bearing boards for use in dry conditions. Theproperties of the composite covered with poplar veneer exceed the demanded values of theparticleboard for heavy-duty load-bearing boards for use in humid conditions according GB／T4897.