Search

This research investigated the influence of the layered structure of paper on its selected strength properties. Two types of cellulose pulp were used: unbleached kraft pine pulp (UBSK) and unrefined bleached birch kraft pulp (BHK). Multi-ply papers were obtained from layers of appropriate grammage formed separately and bonded in a wet state. Paper layers were formed from primary pulps (UBSK and BHK) or their mixtures (threeply UBSK-BHK paper and three-ply UBSK-BHK-UBSK paper), from which various variants of laboratory paper samples were made. This work focused on three-layer papers. The obtained laboratory sheets were analysed for changes in tear resistance, tensile strength, bursting strength, short span compression strength (SCT), and corrugating medium test (CMT). In most cases, three-layer structures were characterised by higher strength parameters than single-layer papers. The tear strength and SCT of papers consisting of three layers formed from both mixed pulps were slightly lower than those of solid papers. The results demonstrate the feasibility of producing three-ply paper with significantly reduced variability in parameters such as elongation and bursting strength, which are inherently subject to high variability. [ABSTRACT FROM AUTHOR]

Chemical crosslinking is an established method for improving the wet performance of paper. In the chemical crosslinking process, covalent bonds are formed between cellulosic surfaces. The formed intra- and interfiber bonds increase the paper's wet strength and reduce its water absorptivity. The majority of published studies concern crosslinking treatments with glyoxal, citric acid (CA), or with 1,2,3,4-butanetetracarboxylic acid (BTCA). The most severe disadvantage of the crosslinking treatments with glyoxal, CA, and BTCA is that the formed crosslinks make the fibers and the paper more brittle. This downside effect has largely impeded the utilization of crosslinking in paper and paperboard making. In the present study, handsheets made from Nordic bleached softwood kraft pulp (NBSK) were crosslinked with methylated 1,3-dimethylol-4,5-dihydroxyethylene urea (mDMDHEU), which is commonly used in cotton fabric finishing. Similar to using glyoxal and citric acid, crosslinking with mDMDHEU notably increased the handsheet wet strength and decreased the water absorption. Compared to the use of glyoxal or CA, the crosslinking with mDMDHEU did not make the handsheets that brittle. These results suggest that mDMDHEU could be a more viable crosslinking agent for improving the wet performance of paper products. [ABSTRACT FROM AUTHOR]

Paper properties determine the product application potential and depend on the raw material, pulping conditions, and pulp refining. The aim of this study was to construct mathematical models that predict quantitative relations between the paper density and various mechanical and optical properties of the paper. A dataset of properties of paper handsheets produced with pulps of Acacia dealbata, Acacia melanoxylon, and Eucalyptus globulus beaten at 500, 2500, and 4500 revolutions was used. Unsupervised classification techniques were combined to assess the need to perform separated prediction models for each species, and multivariable regression techniques were used to establish such prediction models. It was possible to develop models with a high goodness of fit using paper density as the independent variable (or predictor) for all variables except tear index and zero-span tensile strength, both dry and wet. [ABSTRACT FROM AUTHOR]

The objective of this study was to characterize the properties of pulp and paper produced from tea (Camellia sinensis) wastes, an agricultural residue widely available in Turkey, using the kraft-anthraquinone (AQ) cooking method. The chemical components and fiber morphology of tea wastes were investigated. The results indicated that tea wastes had low holocellulose, cellulose, and a-cellulose contents and high lignin content. Also, the suitability of the fiber for pulp and paper production was examined, and the fiber length, fiber width, lumen diameter, and cell wall thickness were measured. According to these values, it was found that the strength properties of papers obtained from tea wastes were insufficient. Therefore, tea waste pulps were mixed with Turkish pine pulps at various ratios. Twelve different cooking experiments were performed on the tea wastes, and the cooking with the best pulp yield was used for mixing. The second cooking, with 0.1% AQ, gave the best yield (33.26%), an increase of about 3.51% compared to the first cooking with no AQ. The physical and optical properties of the papers were also examined. Results showed that paper properties were improved by increasing the Turkish pine pulp rate. Consequently, tea wastes can be used in pulp and paper production when combined with softwood pulps. [ABSTRACT FROM AUTHOR]

The present study shows that barley straw (Hordeum vulgare) can be a supplementary raw material of softwoods and hardwoods such as Pinus sylvestris and Eucalyptus camaldulensis, respectively, for the production of cellulose and paper, reducing an agricultural residue that has no added value. Barley straw has a lower content of cellulose at 36.4% than P. sylvestris and E. camaldulensis, but it contains a lower quantity of lignin, 15.9%. After pulping with soda anthraquinone (AQ), high contents of cellulose (56.5 to 67.5%) and holocellulose (>80%) were attained. Paper sheet properties were able to reach, and even improve upon, those of wood species (Pinus and Eucalyptus) pulped with kraft. Better values of total yield (56.5%), Kappa number (8.9), and ISO brightness (36.4%), were attained for paper sheets from barley straw pulp versus E. camaldulensis and P. sylvestris, respectively, and comparable values for viscosity, tensile, and burst index were obtained. [ABSTRACT FROM AUTHOR]

A variety of the Leucaena genus, Leucaena diversifolia, was used for pulp and paper making by kraft and refining processes and a OD(EP)DP bleaching sequence. The same species has been suggested as an energy crop and, in fact, this species used shows a high gross heating value; besides, this variety of Leucaena has appropriate characteristics for pulp and paper making. The holocellulose content was higher than Eucalyptus globulus, and ash and lignin contents were comparable to other varieties of Leucaena. Pulps with a kappa number between 17 and 18, and 21.4 cP viscosity were obtained using an active alkali concentration of 31%. Also, paper sheets showed good strength properties, comparable or even greater than those obtained with Eucalyptus or others varieties of Leucaena at comparable refining degrees, between 30 and 40 °SR. The pulp was successfully bleached in all cases with a kappa number below 1.5 in the EP stage and a value of brightness higher than 90%. [ABSTRACT FROM AUTHOR]

The purpose of this investigation was to study the effect of fiber characteristics, especially fiber wall thickness, on the hygroexpansion behavior of paper due to humidity changes. Five different eucalyptus Kraft pulp samples were studied with an OPTIDIM hygroexpansivity tester. As a reference, birch and acacia were included. In all, seven pulp samples were refined at low consistency (LC), using a Voith Sulzer refiner. Both anisotropic and isotropic sheets were investigated. The sheets were dried under restraint. The results showed that fiber wall thickness is an important factor in controlling the hygroexpansivity of paper through fiber network activation. [ABSTRACT FROM AUTHOR]