สำนักราชบัณฑิตยสภา

243 Somporn Chaiarrekij et al วารสารราชบัณฑิตยสถาน ปีที่ ๓๗ ฉบับที่ ๑ ม.ค.-มี.ค. ๒๕๕๕ handsheets with higher opacity while the opposite results were obtained from the softwood pulp. Opacity could be lower when longer fibers like softwood and kapok pulps were added into the pulp mixture since the surface areas for light scattering were smaller. This could be clearly seen for the case of softwood pulp. However, when the kapok pulp was added, the yellowness of the pulp seemed to overcome the effects of its length and this led to lower opacity instead. Density Paper made from 100% softwood pulp had highest density (0.627 g/m 3 ) while that from 100% kapok pulp had lowest density (0.525 g/m 3 ). Although both pulps contained long fiber which should contribute to higher density due to more contact areas for inter-fiber bonding, kapok fibers were then entangled and provided a poor paper formation. This might be the reason for the low density of 100% kapok handsheets (Figure 4). It was also found that the effect of recycling cycles on density was quite small as compared to the effects of pulp type and the amount of pulp added. The more kapok or softwood pulp was added, the denser handsheets became. This might be because the better fiber bonding was obtained by adding long fibers into the short fibers of 100% recycled pulp. Figure 3 The Effects of Recycling Cycles, Kapok Pulp and Softwood (SW) Pulp on Opacity (Note: Kapok and SW pulps have opacity values of 69.19% and 82.05%, respectively)