WOOD RESEARCH Volume 69, Number 1, 2024
VLADIMÍR IHNÁT, HENRICH LÜBKE, RASTISLAV ČEREŠŇA, JOZEF BALBERČÁK, VLADIMÍR KUŇA, ANDREJ PAŽITNÝ, and ŠTEFAN BOHÁČEK

THIN LIGNOCELLULOSIC LINERS BASED OF SPRUCE SHAVINGS

The article is devoted to determining the basic physical and mechanical properties of sheet materials up to 1.5 mm thick based on wood shavings and PVAc glue with a high proportion of water, pressed under high pressure up to 25 MPa and a temperature of around 190°C, so that the softening of lignin caused by the generated steam, allow to create a compact and non-crumbling surface. In order to characterize the physical-mechanical properties of the new wood-based sheet material with minimum thickness and characteristic elasticity, tests according to the CEPI (Confederation of European Paper Industries) standards were adopted. Procedures for tensile strength according to ISO 1924-2 (2008), Burst strength according to ISO 2758 (2014), puncture according to ASTM D781-68 (1973), water absorption according to ISO 5637 (1989) and porosity according to TAPPI Test method T460 were applied

WOOD RESEARCH Volume 69, Number 1, 2024
JOZEF BALBERČÁK and VLADIMÍR KUŇA

MODIFIED STARCHES AS A MEAN OF INCREASING THE DRY STRENGTH OF TISSUE PAPERS

Application of agents to increase the dry strength is one of the ways of improving the physical-mechanical properties of papers. In the presented article, we are dealing with the application of modified starches to the pulp mass in order to increase the strength parameters of hygienic papers. In laboratory experiments, 8 types of agents were tested, which differed in charge level, molecular weight and cross-linker level. Strength parameters, porosity and water absorption were evaluated during the laboratory tests. The most important strength parameter in the production of tissue papers is the tensile strength, the most suitable parameters for the production of tissue papers were achieved when applying the product ECO 2777. By monitoring the influence of the dose of starch, it was found that the optimal dose is 3 kg per ton of absolutely dry pulp, when there is an increase in the tensile strength by 18%, the burst strength by 41% and while maintaining the required values of stiffness, porosity and water absorption

WOOD RESEARCH Volume 67, Number 2, 2022
Sefa Durmaz

Effect of wood flour content on the properties of flat pressed wood plastic composites

This study focused on the effect of wood flour content on some mechanical and physical properties of flat pressed wood plastic composites (WPC). The results revealed changes in the wood flour content affected the density of flat pressed WPC. Moreover, as exposure time increased, water absorption values were increased. The changes in the wood flour content considerably affected the mechanical properties of WPC. The decrease in the flexural strength reached up to 58%, while it was 61% for tensile strength. However, modulus of elasticity increased with increasing wood flour content. Meanwhile, the decrease was inevitable for screw withdrawal strength, where the increase in wood flour content resulted in a reduction of up to 50%. It was clearly determined that wood flour content above 60% evidently affects the physical and mechanical properties of flat pressed WPC, which should be considered in the utilization areas where high mechanical properties are critical.

WOOD RESEARCH Volume 67, Number 1, 2022
Khawaja Adeel Tariq, Muhammad Haroon, Abdullah Habib Mughal, and Sher Ali

Physical and mechanical characterization of structural wood used in pakistan

Six species of wood (Vachellia nilotica, Eucalyptus camaldulensis, Ziziphus mauritiana, Albizia lebbeck, Melia azedarach, Dalbergia sissoo) were tested in compression and tension parallel to the grain. The specimens were collected from different areas of Pakistan. The compressive strengths, tension parallel to grain and hardness of the wood were determined by testing rectangular shape wooden specimens (ASTM D143 2014, Janka 1906). It was observed that compressive and tensile strength of Vachllia nilotica parallel to the grain is higher than other species whereas, Eucalyptus camaldulensis hardness behaviour along radial and tangential surface is higher among the wooden samples tested.

WOOD RESEARCH Volume 63, Number 4, 2018
Ming Chen, Xiangmin Li, and Jianhua Lyu

Influence of dowel diameter and curing time on strength of double dowel joint

The tensile and bending strength of double wood dowels in medium density fiberboard components was tested by using experimental method which was conducted to define the influence of dowel diameter and curing time on tensile and bending strength of T-shaped and L-shaped double wood joints. The results showed that the dowel diameter and curing time have a great effect on the tensile and bending strength of T-shaped and L-shaped double wood joints. The obtained optimum technical parameters were respectively as follow: dowel diameter was 10.00 mm for tensile strength of T-shaped joints, dowel diameter was 10.00 mm for bending strength of T-shaped and L-shaped joints, and curing time was 168 h for bending strength of T-shaped and L-shaped joints. The relational expression between dowel diameter R and the tensile strength P was obtained in P= 159.7R+11.05, the relational expressions between dowel diameter R and the bending strength P were obtained in P= 30.7R-58.21 and P= 25.48R-41.04 for T-shaped and L-shaped double wood joints, respectively. Moreover, the relational expression between curing time T and the bending strength P in the P= -0.003T2+0.683T+164.1 and P= -0.003T2+0.746T+132.0 for T-shaped and L-shaped double wood joints, respectively.

WOOD RESEARCH Volume 63, Number 4, 2018
Mária Fišerová, Elena Opálená, Juraj Gigac, and Monika Stankovská

Oxidative and reductive bleaching of deinked pulp

Deinked pulps for hygienic paper production were bleached with hydrogen peroxide and sodium dithionite in single and two-stage bleaching. The brightness gain of high brightness deinked pulp in the peroxide stage was 5.7% ISO and of low brightness 4.4% ISO. In sodium dithionite stage, the brightness gain of high brightness deinked pulp was 4.0% ISO and of low brightness deinked pulp 3.8% ISO. The two-stage oxidative-reductive bleaching sequence resulted in an increase of brightness by 9.7% ISO for high brightness deinked pulp and by 9.1% ISO for low brightness deinked pulp. Brightness gain in the two-stage reductive-oxidative bleaching sequence was 6.7% ISO for high brightness deinked pulp and 5.6% ISO for low brightness deinked pulp. The coordinate b* value and yellowness of deinked pulps decreased in sodium dithionite bleaching stage more than in hydrogen peroxide stage. The two-stage oxidative-reductive bleaching sequence is more preferred than reductive-oxidative sequence regardless of the fibre composition. The tensile index and the tensile energy absorption index of deinked pulps slightly decreased after single-stage and two-stage bleaching sequences, their reduction in the peroxide stage was greater than in the dithionite stage. The fibre strength and fibre length characteristics of deinked pulps decreased after bleaching, while fibre bonding ability increased. The water absorption and bulk softness increased after bleaching, the increase was higher after peroxide stage than dithionite stage.