Physical and Strength Properties of Kraft Pulp Sheet

ISBN : 978-602-17761-4-8 41 Proceedings of 2 nd REPTech Crowne Plaza Hotel, Bandung, November 15-17, 2016 © 2016 Published by Center for Pulp and Paper through 2 nd REPTech woods with higher SV ratios, such as gmelina and sengon Table 1, i.e. de-methylation de-alkilation on fragmented lignins, thereby rendering them more soluble; in addition to the regular deligniication that prevalently occurs through the cleavage of α-O-4 and β-O-4 bonds at the lignin during the kraft cooking [6,10]. This situation induced more intensive iber separation; and explained greater screen- pulp yield and concurrently lower pulp reject from meranti kuning and kapur woods Figures 2c and 2d. Conversely, lignin with lower SV ratio that implied containing more vanillin units Figure 1 such as meranti kuning and meranti, might inlict more possibility on mechanism reaction II condensation between the fragmented lignins that afforded greater-sized fragments aggregates which were less soluble Figure 6. Such phenomena besides retarding deligniication rate intensity could also induce more severe degradation on wood carbohydrates esp. cellulose and hemicellulose. It seemed that such condensation and degradation occurrence contributed their role signiicantly in decreasing the screened-pulp yields from meranti kuning and kapur woods with the elevated H-factor; and also their lower screened-yields than from gmelina and sengon woods Figures 2c. Further beyond 1502.25 H-factor, condensation reaction during the kraft cooking of meranti kuning and kapur woods apparently became more intensive that rendered their pulp rejects increasing to the point which exceeded the rejects from gmelina and sengon Figure 2d.

4.4. Physical and Strength Properties of Kraft Pulp Sheet

Kraft pulp handsheets were only formed and tested from the kraft cooking pulpng at 1502.25 H-factor, as such could achieve the highest screened-pulp yield and lowest pulp reject, particularly from gmelina and sengon woods Figures 2c and 2d. It appeared that highest basis weight and strengths of pulp sheets were from sengon, followed in decreasing order by consecutively gmelina, meranti kuning and kapur Table 3. Such decreasing order was seemingly correlated with the lowering SV ratio at each of the four PF woods R = [+0.5665] - [+0.6542]. This again strengthened the previous indication of active-selective kraft deligniication which became less effective with the more intensive condensation reaction, imperfect iber separation, and more wood carbohydrate degradation, especially for meranti kuning and kapur woods [6,10]. Figure 5. Reaction mechanisms, in which the syringil-type monomer units in the lignin entities during the kraft cooking are partially de-methylated de-alkilated forming more soluble lignin fragments [6,10] Figure 6. Condensation reactions A and B types that can occur between the already fragmented lignins at the unoccupied C-5 position of the vanillin-type monomers during the kraft cooking forming less soluble larger-sized lignin fragments aggregates [10,11] ISBN : 978-602-17761-4-8 42 Proceedings of 2 nd REPTech Crowne Plaza Hotel, Bandung, November 15-17, 2016 © 2016 Published by Center for Pulp and Paper through 2 nd REPTech Correlation between pulp basis weightpulp strengths and wood density also occurred negatively, but less strongly R = [-0.5078] - [-0.5663] compared to the case for SV ratio, whereby the greater the density, then the lower those two pulp properties. This was explicable as wood with low density tended to have thin iber-walls, thereby intensifying iber-to-iber bonds and felting during the sheet forming; and vice versa. On the other hand, insigniicant correlation between initial lignin content and pulp basis weightstrengths R ns = [+0.3219] - [+0.4646] seemed strongly attributable to the insigniicant correlation between lignin content and deligniication intensity Figure 3c Tabel 3. Basis weight and strength properties of unbeaten kraft pulp from four plantation forest’s wood species [8] 1 Wood species Basis weight gm 2 Tear factor mN.m 2 g Breaking length Km Sengon 61.55 5.09 5.55 Gmelina 61.13 2.29 2.67 Meranti kuning 61.08 0.33 0.36 Kapur 57.23 0.24 0.26 Correlation R with SyringilVanillin Ratio: + 0.5857 + 0.6542 + 0.5665 Highest Correlation R with Wood Basic Density: - 0.5391 - 0.5663 - 0.5078 ns Second Highest Correlation R with Lignin Content: + 0,3219 ns + 0,4646 ns + 0,4518 ns Lowest 1 Average of 5 replications

4. Conclusions and Suggestions