The Extraction Of Tube Fibre And Nanofibril From Coir Fibre And Their Structural Analysis

Coir fibre is very rich as a sort of green and renewable resource, however, coir fibres were used just as a sort of crude fibres because of the lack of its microstructure research. The main aim of the work was to prepare nanocellulose whiskers, separate tube fibres and study the structure to provide the application method for coir fibres and tube fibres.One of the work was to prepare the nanocellulose whiskers(NCWs) by oxidation. The whiskers at the smallest diameter is approximate to 6 nm at thickness, which is protofibril and generally in the range of 6~10nm. The whiskers at the largest diameter is approximate to 40 nm,which is microfibril and in the range of 20~40nm in diameter. The type of coir fibres was celluloseⅠ and the sodium hypochlorite-sodium hydroxide solution was more efficient to rise the crystallinity of coir fibres. Besides, the crystallinity of nanocellulose whiskers was about 52%,which is close to the value of theoretical model estimation. Thus the nanocellulose whiskers was considered as pure cellulose. The content of cellulose, hemicellulose and lignin in coir fibre used in the experiment were respectively 39.2%,28.4% and 25.4% according to infrared microscope test.Dissolve the intercellular matrix between tube fibres accompanied by ultrasonic oscillations,then tube fibres began to split. When the intercellular matrix was completely removed, the tube fibres were extracted successfully and the preparation rate was 23%. The tube fibres were9.62~19.23 μm in diameter, 250~1394 μm in length and the length-diameter ratio reached 36~200,which was hard to spin, while the length-diameter ratio of helical crystal ribbon is in the range of103~104, which was easy to spin if the helical crystal was prepared.Two models were established and they were the packing structural model of the helical crystal ribbon and the multilever fibril model of the helical crystal ribbon.The packing structural model of the helical crystal ribbon is shown that the tube fiber is composed of a right-handed helical crystal ribbon cohered with inter-ribbon matrix and with outside and inner surface layer. Tube wall is composed of three layers, namely outer-layer, ribbonlayer, and inner-layer in the cross section. The thickness of outer-layer and inner-layer was estimated to 2:1.The multilevel fibril model of a helical ribbon in tube fiber is showed that i) the model of the one-crystal(in a- & c-axis) whisker is introduced, which is the whisker of Cellulose I, i.e. a linear crystal of ac(bn)= 8.35?×7.9?×10.3?n, where n is the degree of polymerization; ii) based on the linear crystal model, the protofibril model is produced, which is a single-crystal protofibril packed with 85 one-crystal whiskers in regular, i.e. 6.68nm×3.95 nm protofibril, that’s coincident with the smallest diameter of the protofibrils measured, and sometime, the four corners would be in disorder, so it is also a linear single crystal; iii) the microfibril model is composed of 54 protofibrils with the interval of one-crystal-whisker’s thickness, i.e. 0.835 nm(a-axis) 0.79nm(c-axis), and sometime, the protofibrils at four corners would be incomplete crystals or replaced with amorphous region; and iv) the microfibrils are packed together in lattice or random, or compositing of the two alignments to form a helical crystal ribbon, and there are 12~40microfibrils in ribbon-thickness; 50~70 microfibrils in ribbon-width, and 600~2800 microfibrils in the cross-section of a crystal ribbon.Structure determines properties. The research in structure of coir fibre and tube fibre is useful to analyze their properties and be put into use.