Evaluation of malubago (Hibiscus tiliaceus L.) for pulp and paper manufacture.

Malubago (Hibiscus tiliaceus L.) was found to have a cell wall specific gravity at oven dry conditions of 0.74 and a wood specific gravity of 0.39 and 0.30 at oven dry condition and fiber saturation point, respectively. The percent shrinkage was computed to be 9.6 percent. During the chemical analysis the samples with 10.9 percent bark had higher extractive and lignin content, exhibited greater 1 percent NaOH solubility, and had a lower holocellulose content. The sample with bark showed a slightly higher fiber length, thinner cell walls, larger fiber and lumen widths. Malubago fibers had a Runkel ratio in the range of 0.684 to 0.982. The pulping of malubago had an average yield of 39.3 percent and 39.8 percent at an active alkali of 14 percent and 16 percent, respectively. The kappa number of the pulp was on the average 22.6 and 12.9 while its percent rejects was 0.5 percent and 0.6 percent for 14 percent and 16 percent active alkali, respectively. The treatment without and with the bark gave average yields of 40.0 percent and 39.8 percent, respectively, while having a reject and kappa number of 0.58 percent, 17.4, and 0.48 percent, 18.6, respectively. The treatment without and with the addition of the additive, sodium borohydride gave the following results: a yield of 40.8 percent (without the additive) and 39.19 percent (with the additive), a kappa number of 17.2 (without the additive) and 18.2 (with the additive), and rejects of 0.60 percent (without the additive) and 0.47 percent (with the additive). A range of 2000-3000 revolutions was required to attain a 300 ml CSF (Canadian Standard Freeness) in a PFI mill. Its handsheets exhibited an average burst index of 7.5 kPa sq.m./g, tear index of 14.6 mN, sq.m./g, tensile index of 73.7 N. m/g, folding endurance of 1072 and density of 0.6 g/cu.cm. In the statistical analysis, the burst index of WA had a significantly higher values. The addition of bark significantly reduced the folding endurance, while the addition of NaBH4 significantly increased the burst index and at the same time decreased the yield, but at the same time, the addition of the additive prevented excessive peeling reaction to take place. This is evidenced by the fact that treatments with sodium borohydride had greater fiber fractions and less fines. The increase in active alkali significantly lowered the kappa number, increased the burst index and the folding endurance. Malubago handsheets had greater burst index than abaca (Musa textilis) and excellent tear index compared to both abaca and excellent tear index compared to both abaca and Mollucan sau (Paraseriantes falcataria). It also met the tensile strength requirements of the Philippine NatD, Los Banos, Laguna (Philippines).