A morphological study on the behavior of bamboo pulp fibers in the beating process

Bamboo pulp fibers respond to beating more rapidly than do wood fibers. This is probably due to the difference in secondary wall structure between the fibers. In the present paper, the behavior on beating of pulp fibers from Bambusa polymorpha Munro was investigated from a morphological point of view. The secondary wall of bamboo fibers consists of alternately arranged broad and narrow layers. During the beating process, a number of transverse and concentric cracks are generated in the broad layers, which causes an internal fibrillation. The outer broad layers with their numerous cracks separate from the inner layers and swell highly toward the outside. The outer secondary wall layer of bamboo fibers has a microfibril angle of about 20° with respect to the fiber axis which is much smaller than that of the S1 layer of wood fibers. As a result this layer appears to offer little resistance to prevent the external swelling of the broad layers.