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Series: De Gruyter STEM
Emerging Bio-Precursors for Chemical Processes

Abstract

Polylactic acid fibrils (PLAf) were employed as a fiber component in papermaking. The addition of 5 wt % of PLAf to bleached kraft birch pulp increased the tensile index of the resulting 100 g/m2 paper sheets by 20 % in comparison to sheets produced without PLAf. By heat-treating the paper sheets containing 5 wt % PLAf, a 35 % higher tensile index in comparison to sheets produced without PLAf was achieved. SEM imaging showed that the heat-treatment caused the PLAf to melt, which formed a film on the fiber web. The PLAf was ultrasonicated in an attempt to make its surface more hydrophilic and anionic and thus more compatible with cellulose. Chemical additives (cationic polyacrylamide, polyethylene imine and polyethylene glycol) were added to the PLAf/cellulose pulp mixture in order to increase the binding between the ultrasonicated PLAf and cellulose. Ultrasonication caused the PLAf length to decrease and the PLAf surface charge changed by 36 %, indicating that the PLAf became significantly more anionic. Neither ultrasonication of PLAf nor the chemical additives improved the paper sheets’ stretchability. Polyethyleneimine as an additive in an amount of 1 % increased the tensile index of heat-treated sheets made with 5 wt % of PLAf by 19 %.

Abstract

Anatomical, morphological and chemical characteristics of kaun straw were examined to assess their suitability for paper production and the properties were compared with wheat straw and rice straw. It was found that the fiber length of kaun straw is slightly shorter than that of wheat straw and longer than that of rice straw. It has wider fiber wall thickness than that of wheat straw and rice straw. It had acceptable derived values, especially slenderness ratio, which was lower than that of wheat straw and rice straw, and higher runkel ratio and lower flexibility coefficient. Chemical analysis of kaun straw revealed satisfactory levels of α-cellulose content (35.9 %) and klason lignin content (19.3 %). The ash content in kaun straw (7.32 %) showed lower value than that of wheat straw and rice straw. In optimum cooing conditions, kaun straw produced pulp yield of 30.0 % and 41.7 % with kappa number 15.1 and 22.5 in soda-AQ and formic acid pulping processes, respectively, the values of which were lower than that of wheat straw and rice straw.

Abstract

The hypothesis is that it should be possible to modify papermaking conditions in line with the softening properties of high yield pulp fibres and achieve similar strength properties to conventional chemical pulp based paper. We therefore investigated the rheological and physical properties of high yield pulp based papers during hot-pressing. Our results confirm that increased temperature combined with sufficient pressure enables permanent densification by softening of lignin, producing very high tensile strength. This treatment also significantly improved the wet tensile strength in comparison to bleached kraft pulp without using wet strength agents. The high yield pulps used here were spruce based thermomechanical pulp, chemi-thermomechanical pulp, and high temperature chemi-thermomechanical pulp, and birch-aspen based neutral sulphite semi chemical pulp, with spruce-pine based bleached kraft pulp as reference. Rapid Köhten sheets of $150g/m2$ and 50 % dryness were hot-pressed in a cylinder-press at 20–200 °C, 7 MPa, and 1 m/min. The mechanical properties showed great improvements in these high yield pulp papers, with tensile index increased to 75 kNm/kg and compression strength index to 45 kNm/kg; levels close to and better than bleached kraft. Wet strength increased to 16 Nm/g compared to 5 Nm/g for bleached kraft.