In this study, the effects of sodium borohydride (NaBH4) on properties of kraft pulp and paper obtained from European black pine (Pinus nigra Arn.) were investigated. Kraft−NaBH4 cookings were done under fixed cooking conditions by adding NaBH4 in the amounts of 0.5%, 1%, 1.5%, and 2% (oven-dried wood) to the cooking liquor. NaBH4-free kraft cooking was carried out as control. The results indicated that addition of NaBH4 to cooking liquor increased the pulp yield. However, the kappa number of pulp and beating time decreased. The brightness of kraft−NaBH4 papers was found to be higher than that of control papers. Addition of NaBH4 significantly decreased pulp viscosity and slightly decreased strength properties of papers.

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In this study, cationic starch (CS) was added to softwood kraft pulps at different degrees of beating in order to evaluate their effects on the strength properties of the pulp. Handsheets were prepared by using three levels of CS addition (0.75, 1.5, and 2.25% CS with respect to oven‐dry pulp) to kraft pulps at different beating degrees (15, 20, 25, and 30° SR). It was found that the tensile and burst indices improved with beating, CS addition, and a combination of these two applications, while the tear index decreased. Remarkable increases in burst and tensile indices were achieved with a 0.75% addition of CS to 15° SR and 20° SR pulps, while notable decreases in tear index was obtained at the same conditions. A gradual tendency was observed in higher beating degrees (25° SR and 30° SR) and higher CS additions (1.50 and 2.25%).

Chemical and anatomical properties of tumorous and normal wood of Quercus robur L. subsp. robur were compared. Tumorous growth appeared as a result of topping stress. Orientation of cells was severely disrupted in the affected wood. In cross section, aspects of cells changed abruptly from transverse to longitudinal, and in tangential section all wood elements appeared to turn around each other like a fingerprint. Vessel elements and fibres of affected wood were shorter than those of healthy wood. The vessels of affected wood were smaller in diameter especially in the earlywood. On the other hand, multiseriate ray height was shorter than that of normal wood. In addition, perforated ray cells occurred. The ray and axial parenchyma cells of tumorous wood contained dark coloured phenolic compounds. Normal wood had calcium oxalate crystals, while tumorous wood did not. Chemical analyses showed that hemicellulose content and solubility rates in 1% NaOH, cold water, hot water, and alcohol- benzene were higher than those of normal wood. Cellulose and ash contents of tumorous wood were slightly lower than in normal wood. In addition, air-dry specific gravity of tumorous wood was higher than that of normal wood.

In this study, Pinus pinaster and Populus tremula chip mixtures were kraft cooked and resulting pulp and paper properties were investigated. The chemical properties and fiber morphology of both species were examined. Cooks were made for five different pine/aspen chip mixtures (0, 25, 50, 75, and 100%). Results of this study showed that pulps with higher kappa number, viscosity, and reject ratio were observed for chips mixtures with higher pine ratio. Higher pine in the mixture resulted in lower total and screened yield. Increase in poplar ratio in mixture gave pulps that were easier to beat. Pine chips improved the strength properties and lowered the brightness and smoothness.