EFFECT OF BAMBOO AGE ON THE PULPING PROPERTIES OF BAMBUSA STENOSTACHYA HACKEL

摘要

This study investigated the effects of stem age of thorny bamboo (Bambusa stenostachya) on the results of different cooking methods, conditions, bleaching conditions, and handsheet properties. The stems of 0.2-, 1.2- and 3-year-old thorny bamboo were separately cooked by kraft and soda processes. The resulting pulps were then subjected to a single-stage hypochlorite bleaching. The unbleached and bleached pulps were beaten with PFI mill to 400 mL CSF, formed into handsheets and then compared as to their properties. Chemical analyses indicated that lignin content increased with increasing bamboo age, while holocellulose and pentosans showed a contrary trend. The results of kraft and soda cooking indicated that mature (3-year-old) bamboo was difficult to digest. Although pulp yields were fairly high (55%), a substantial portion (22.4%) consisted in shives and coarse materials. At identical chemical charges, the mature stems produced pulp with higher kappa number (28.2) than that of the youngest stems (22.9). The bleaching results indicated that young, tender stems produced pulps with better brightness gains, and also the bleached pulps had lower kappa numbers. At a hypochlorite charge of 10%, pulps from the young bamboo stems reached a brightness of 74% ISO. The pulps from mature stems, however, barely reached a brightness of 55% ISO. As to pulp handsheet strength properties, the pulps made from young stems retained the best properties. Pups from mature bamboo stems Were more difficult to bleach and if more severe bleaching conditions were applied, the pulp strength properties suffered a higher extent of degradation. Therefore, to garner benefits of both brightness and strengths, only younger than 1-year-old bamboo stems should be used for pulping and papermaking, as they have both adequate strengths and brightness needed for fine paper.