| The cotton stalk, byproduct of cotton, is renewable resource available in abundantquantity around the world. The cotton stalk bark accounts for26percent of cotton stalk’sweight, and contains a lot of cellulose, lignin and hemicellulose, is a valuable nature materials.However, the cotton stalks have not been made full use at present. Therefore, it is a promisingwork to explore the cotton stalks and develop its composite materials due to its biodegradable,low cost and abundant reserve, the development of plant fiber and reinforced polymercomposite materials is a hot direction in the research of scholars at home and abroad in recentyears. In this paper, we base on ecology and green environmental protection, study thepreparation technology of cotton stalk fibers and use the obtained cotton stalk fibers toprepare the polypropylene composite.Firstly, the cotton stalk fibers were prepared from steam flash-explosion (SFE) method.Especially, the effect of steaming pressure (1.5MPa,2.0MPa,2.5MPa,3.0MPa,3.5MPa）oncomposition, crystalline structure, morphology, hygroscopic properties, tensile strength andthermal performance of cotton stalk fibers were investigated. The results indicate that thecotton stalk fibers become finer and possess relatively cleaner surface with the steamingpressure increasing. At the same time, cellulose content in cotton stalk bark fiber presentsincrease and level off tendency. Besides, the results also show that the SFE method do notchange the cotton stalk fiber’s crystal structure, and all of the cotton stalk fibers still maintainthe structure of cellulose Ⅰ. But, the thermal property of prepared cotton stalk bark fibers isincreased by SFE. Results indicate that the optimum steam pressure is2.5MPa whensteaming time is set to2min for extracting cotton stalk fibers. Under the optimized conditions,the obtained cotton stalk fibers possess cellulose content of72%, length of48mm, fineness of45dtex, crystallinity index of68, moisture regain of8%, water retention of98%, tensilestrength of2.4cN/dtex, and yield of41%Secondly, the combine method of SFE and Alkali(AT) treatment(SFE-AT) was applied toproduce cotton stalk bark fibers, and the effect of steam pressure and Alkali concentration tothe length, fineness and tensile strength of cotton stalk fibers was analyzed. The optimalprocess for preparing the cotton stalk fibers was obtained: steam pressure is2MPa, retentiontime is2min and sodium hydroxide concentration is6g/L, under the best conditions, thelength, fineness and tensile strength of cotton stalk fibers are53mm,29dtex and2.6cN/dtexrespectively. The optimal process was also compared with AT, SFE respectively. The effectof different treated methods on composition, crystalline structure, morphology, tensilestrength and thermal performance of cotton stalk fibers were investigated. The results indicate that the combination of steam flash-explosion and alkali treatment was better than the othertwo methodsFinally, the cotton stalk fibers produced in different conditions were used to preparecotton stalk fibers/polypropylene(PP) composites. The effect of cotton stalk fibers’composition and morphology to mechanical properties of composites was investigated. SEMwas used to observe the interfacial bonding of cotton stalk fibers and PP. The results indicatethat the PP composites reinforced by cotton stalk fibers from SFE-AT possess highestmechanical properties and stability to water compare with the reinforcement from AT and SFE.From this point, ultra-lightweight PP composites can be prepared with the cotton stalk fibersby SFE-AT.The combine method of SFE and Alkali(AT) treatment is an effective way to preparecotton stalk fibers with good quality and reduce the chemical used at the same time, moreover,the obtained cotton stalk fibers can also be used to prepare the light PP composite materials,which have potential application in the automotive, construction and packaging industry. So,it is significant to develop the cotton stalks bark and explore the relevant composite materials. |
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