สำนักราชบัณฑิตยสภา

245 Somporn Chaiarrekij et al วารสารราชบัณฑิตยสถาน ปีที่ ๓๗ ฉบับที่ ๑ ม.ค.-มี.ค. ๒๕๕๕ Porosity of handsheets was determined by measuring the air resistance of handsheets. Porous paper has less air resistance and the time allowing air to pass through is quite short. As can be seen from Figure 5, it was clear that recycled fibers offered paper with lowest air resistance time or highest porosity because of the poor fiber bonding. Kapok pulp provided handsheets with highest air resistance time or lowest porosity as compared to softwood pulp because of its longer fiber length. Recycling paper up to 3 cycles did not impose a strong impact on porosity while pulp type and percentage did. Since kapok pulp itself had the highest air resistance time or lowest po- rosity, the paper containing kapok fibers had much lower porosity than that containing softwood pulp at the same ratio. Tensile index Tensile index is defined as tensile strength divided by grammage. The results from Figure 6 indicate that paper made from 100% kapok pulp was strongest as depicted by its highest tensile index (86.35 Nm/g) due to its outstanding fiber strength. Paper made from 100% recycled pulp was weakest as expected since fibers were destroyed during the recycling process. Also, the numbers of recycling cycles had a small impact on tensile index. Both kapok and softwood pulps seemed Figure 6 The Effects of Recycling Cycles, Kapok Pulp and Softwood (SW) Pulp on Tensile Index (Note: Kapok and SW pulps have tensile index values of 86.35 Nm/g and 51/85 Nm/g. respectively)