| Natural bamboo fiber has been applied in composite materials, textiles, and other fields. There are already some reports about its extraction, morphology and property, but those reports are main about more than 4 years old bamboo, and the bamboo used in actual production are always more than 4years old, too. Bamboo shoots can reach the height of mature bamboo in 2 or 3 months, and its volume do not change significantly in the following years. It is the texture of the bamboo that change a lot in the following years. The change of texture has a vital influence on many aspects of bamboo performance. Therefore, this paper, aims at investigating the extraction of natural bamboo fiber bundle, the changes of the chemical composition and performance of the young bamboo fiber during the growth, in order to guide the production practice, to provide a theoretical basis for bamboo, bamboo fiber development and utilization.In this paper, the research objects are different age immature Moso bamboos. With rational experimental design, through chemical analysis methods and the usage of modern means of fourier infrared spectrometer, X- ray diffraction analysis, environmental scanning electron microscopy, digital electronic universal testing machine, this paper explores the changes of chemical composition, morphology, crystallinity of cellulose, the degree of polymerization, strength of different age immature bamboo fiber during the growth, and the conclusions are as follows.(1) Moisture content of this year bamboo is the highest. There is no big difference of moisture content between 3 years old and 4years old bamboo. Regarding ease or complexity of defibering and devillicate, rigidity and color and yield of fiber as evaluation indexs, explore the alkali cooking process, and finalize the alkali cooking time and temperature, alkali concentration during the fiber extraction process of this year, 1 year, 2 years, 3 years, 4 years old Moso bamboo as follows, 60 min, 85℃ and 1%, 60 min, 75℃ and 3%, 60 min, 75℃ and 3%, 60 min, 85℃ and 3%, 60 min, 85℃ and 3%.(2) The variations of relationship between cellulose content of fiber of different heights in immature and the bamboo age are as follows, from this year to 3 years old, fiber of different hights are all increasing with different growth rate; from 3 years old to 4 years old, fiber in the middle of bamboo increases slightly, but fiber in the upper and lower part of the bamboo begin to decrease. This shows that around 3 years old fiber cellulose content of each part of bamboo has basically reached the maximum value. From this year to 4 years old lignin content of fiber of different heights in immature bamboo is increasing with the increase of bamboo age.(3) Through the infrared spectrum analysis, it is found that majority of hemicellulose and partial lignin in bamboo are removed during the fiber extraction process, and a small amount of cellulose degrades, but the relative amount of cellulose increases. By environmental scanning electron microscope observation, it is concluded that natural bamboo fiber has many fine grooves and cross-section on longitudinal surface, and most of the cross-section is circular and there is a gap in the middle. With the increase of bamboo age, the gaps in the middle of the cross-section becoming smaller, the densification degree increases, and the diameter of the single fiber distributes more uniform.(4) Viscosity method are used to measure the degree of polymerization(DP) of fiber cellulose in different part of immature Moso bamboo, it is found that from this year to 2 years old DP of fibers cellulose in the lower and middle part keep increasing, DP of fiber cellulose in the lower part reach the peak at 2240, then it begins to decrease; DP of fiber cellulose in the middle reach the peak on 3 years old at 2283, then it begins to decrease, too; fiber in the upper part keep increasing from this year to 4 years old and reach 2576. This indicates that DP of fiber cellulose between 2years old and 3 years old nearly reaches optimum. From the lower part to the upper part of the bamboo, increase of fiber cellulose DP shows lag phenomenon. In other words, cellulose DP of fiber the lower part of bamboo reach maximum first, followed by the middle and upper part.(5) Through the X-ray diffraction analysis, it is found that the extraction processes do not change the cellulose crystal type of fiber; from this year to 3 years old the degree of crystallinity of fiber in each part of bamboo show an increasing tendency; after 3 years old they start to decrease; this indicates that DP of fiber reaches optimum in 3 years old.(6) The fineness determination of different age bamboo fiber shows that fiber fineness is between 33.72 dtex to 58.17 dtex. The fineness of fibers increase and the extraction condition needs to be more severe with the increasing of bamboo age.(7) From this year to 3 years old, tensile strength of fiber in different part of bamboo increase with the increase of age, tensile strength of fiber in the lower and middle part of bamboo reach the peak of 4.08cN/dtex at 3 years old, and then both of them start to decrease; tensile strength of fiber in the upper part of bamboo keep increase from 3years old to 4 years old and exceeds the tensile strength of fiber in lower and middle part. In a word, tensile strength of Moso bamboo fiber reaches optimum at 3 years old and can be cut down for utilization. With the increase of bamboo age, the tensile strength variation tendency of fier in different part of bamboo changes, too.All in all, the cellulose content, lignin content, polymerization, crystallinity, tensile strength of 3 years old bamboo fiber reach the maximum value, and can be cut down for utilization. |
