The Effect Of Steam Explosion Pretreatment On The Properties Of Kenaf Fiber And Its Microscopic Mechanism

With the improvement of material lives, people pay more and more attention to wearing comfort. Products made of ramie, flax and hemp are preferred because of their excellent moisture absorption, air permeability and special style. Steam explosion is proved to be an effective method for the pretreatment of biomass and has been used widely recent years. For the purpose of the development of new fibers and improvement of degumming process, we pretreated kenaf fibers by steam explosion and investigated the effect of steam pressure, maintaining time and moisture content on the physical,chemical and structural properties of steam exploded kenaf fibers. Also, we studied the changes of microstructure of kenaf during steam explosion process by SEM, XRD, FTIR and FTIR-images. The results of the research were as follows:1. Kenaf fibers were pretreated by steam explosion at different steam pressure. With the increase of steam pressure(not higher than 3 MPa), hemicellulose and acid-soluble lignin contents reduced gradually and the percentage of cellulose and acid-insoluble lignin increased gradually, the degree of crystallinity, degree of polymerization and break strength got increased. But An excessive pressure could destroy cellulose structure.2. Kenaf fibers were pretreated by steam explosion at different maintaining time. The content of hemicellulose and pectin decreased, the percentage of cellulose increased and the degree of crystallinity, degree of polymerization and break strength of steam exploded kenaf fibers increased when maintaining time changed from 1 min to 10 min. Maintaining time longer than 15 min was not suggested for degumming of kenaf because of its damage of cellulose structure.3. The effect of moisture content and maintaining time on properties of steam exploded kenaf fibers was also evaluated. When treated by different maintaining time,chemical composition and structural properties had different change trend. When treated under the maintaining time of 1 min, the changes of properties of kenaf were not obvious.If the maintaining time was longer enough, higher content of moisture was not suitable for the degumming of kenaf.4. The microcosmic mechanism of steam explosion pretreatment of kenaf fibers was studied. The results showed that with the increase of steam explosion intensity, the degree of separation of kenaf fibers increased. In the steam explosion process, themacromolecular structure of kenaf fibers had not changed. Hemicellulose and lignin distributed the outer layer of fibers were more easily degraded.