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## 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

Today, the paper industry is faced with a global deficiency of raw wood materials, so alternative sources of virgin cellulose fibres are playing an important role in paper production. Agricultural countries produce large quantities of crop farming by-products such as straw, which is an interesting alternative raw material for cellulose fibres. Straw is used in many industries because of its numerous advantages: animal food industry, biofuel industry, construction industry and as artistic material. The potential use of straw production residues is of great importance in paper and printing industry. The focus of this research is on triticale straw, which was used as a non-wood fibre source for paper production. Namely, triticale straw was converted into semi-chemical pulp and was combined with recycled wood pulp in order to produce alternative laboratory papers. The usability of this kind of laboratory papers in printing industry was analysed based on line reproduction quality. This research evaluated and analysed line reproduction quality based on four line attributes: width, blurriness and raggedness. The results of this research proved that triticale pulp in laboratory papers has equal influence on line printing quality as the recycled wood pulp.

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## 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.

## Abstract

Using disposable screen-printed electrodes is a convenient way of monitoring environmental pollution, production process control etc. Usually, commercially available screen-printed electrodes are used, but more and more studies are being carried out in the field of printing electrodes on thinner, low-cost and versatile substrates, including paper. In the present research, the comparison of screen-printed electrodes printed on different paper-based materials is presented. Two unique and innovative invasive plant-based papers made from (1) Japanese knotweed, (2) Canadian and Giant goldenrod and (3) commercially available cardboard were used as a printing material for the electrodes. The selected paper substrates were characterized, and screen-printed electrodes were printed. The influence of substrates’ properties and pre- or post-treatment of the screen-printed electrodes on the electrochemical behaviour is thoroughly analyzed. The results indicate that the printing substrate (roughness) had the most significant influence on the cyclic voltammetry response. Comparing pre- and post-treatment of screen-printed electrodes, it was shown that grinding influenced the electrochemical activity significantly, while corona discharge does not have as significant influence. Besides, it was shown that the invasive plant-based papers are viable alternatives to commercially available papers and can be used as low-cost and eco-friendly alternatives for disposable screen-printed electrodes.

## Abstract

Although fibrous suspensions are finding increasing use in many applications, holistic studies investigating their material properties are essentially non-existent due to a lack of simple and reliable measurement techniques. To address this, geotechnical techniques have been considered for the characterisation of an extruded suspension of poplar fibres. Use of such characterization techniques was thought suitable since the extruded fibres share many physical similarities with fibrous peats, and since both materials are primarily derived from plants. In the present study, oedometer and direct shear tests were employed to evaluate the compressibility, permeability and friction properties of poplar fibres. Triplicates of each test were carried out for two differently prepared poplar fibres at several different initial water contents. All measurements were found to be in good agreement with the values typical of fibrous peats, justifying direct cross-over of geotechnical techniques as an alternative method for characterising and modelling fibrous suspensions in manufacturing applications.