WOOD RESEARCH Volume 68, Number 4, 2023
Henrich Lübke and Vladimír Ihnát

Technology of Particleboard’s Preparation by Cold Pressing after Hot Mat Compression

The article describes a method of preparing particleboards (PB) from fresh and recycled chips by a new technology of cold pressing after hot compression of the mat according to PCT/SK2023/000007 (ÚPV SR, 13.06.2023) using polyvinyl acetate (PVAc) glue. For comparison, the experiment was also carried out using urea formaldehyde (UF) glue and their mutual combination. The new method shortens hot pressing, or causes reduction of pressing temperatures, while the prepared PB released from pressure no longer spring and cure over time. The curing kinetics of both PVAc and UF adhesives were described by monitoring the flexural strength and modulus of elasticity of PB as a function of time after release of pressure.
Modeling of the PB pressing process based on PVAc glue, which consists of overheating the pressed cross-section of the board to 90°C and its subsequent cooling to a temperature when the board is already stable, i.e. below a temperature of 70°C, was carried out using of a hot and cold press, while the pressing cycle lasted 140 s. Shortening the pressing cycle to 100 s was achieved by applying the glue to the chips already preheated to 92°C. Laboratory tests have confirmed that the mechanical properties of PB are in accordance with the requirements of EN 312/3 for chipboards for interior conditions, including furniture, for use in dry environments.

WOOD RESEARCH Volume 68, Number 2, 2023
Vladimír Ihnát and Henrich Lübke

Water retention of beech shavings heat-treated at lower temperatures

Water retention after 2 hours and 24 hours of soaking in water was determined for beech shavings subjected to heat treatment at temperatures of 120°C, 140°C and 160°C for 2 hours, 4 hours, 6 hours and 8 hours in order to reduce the equilibrium moisture content (EMC) of the wood shavings for use in wood based composites. EMC was determined after 14 days of air conditioning at 23°C and 55% relative humidity. The measured values were compared with the sample dried at 103°C. Water retention was determined after 15 min of centrifugation at 1400 rev.min-1 for a more objective assessment of the wood’s ability to retain water in the cell lumens. The results showed that heat treatment reduces the EMC of beech shavings heat-treated at 160°C for 8 hours in the given conditions from 8.7% to 6.19%. The reduction of EMC at lower temperature was not sufficient enough, especially in the shorter treatment duration of up to 6 hours. In parallel, the reduction of water retention from 65.53% to 47.79% was caused by heat treatment for 8 hours at 160°C.

WOOD RESEARCH Volume 62, Number 5, 2017
Balberčák Jozef, Boháček Štefan, Peter Medo, Vladimír Ihnát, and Henrich Lübke

Chemical processing of waste wood based agglomerates Part I: Evaluation of properties of fluting liners made of semichemical pulp obtained by a mildly alkaline sulphur-free cooking process

The article describes the method of evaluation and preparation of fluting liners produced from semichemical pulp of waste wood particle boards (PB) and oriented strand boards (OSB) and after the combination with old corrugated cardboards (OCC) to improve strength properties. The semichemical pulp was obtained by a mildly alkaline boiling process from two fractions of waste PB and OSB. Properties as thickness, bulk density, gurley, tensile strength, tensile index, breaking length, burst index, CMT30 and SCT were monitored on lab sheets 127 g.m-2 and 170 g.m-2. Values of pH and residual NaOH and Na2CO3 were determined in batch leachate.

WOOD RESEARCH Volume 62, Number 1, 2017
Vladimír Ihnát, Henrich Lübke, Albert Russ, and Vlastimil Borůvka

Waste agglomerated wood materials as a secondary raw material for chipboards and fibreboards. Part i. preparation and characterization of wood chips in terms of their reuse

The article describes a method of preparing particles from waste particle boards (chipboards) and oriented strand boards (OSBs). Their reuse is the main target of recycling. Method of their destruction was determined in this work. Agglomerated materials disintegrated after an initial destruction were further processed under specified conditions with regard to the material humidity, type of materials, contained adhesives and given characteristics of final particles – wood chips. Wood particles obtained were characterized by a fractional composition and amount of residual formaldehyde as an important parameter for the reuse of waste materials in production of furniture boards. New chipboards and pulp for production of middle density fiberboards (MDFs) will be provided from such defined particles.

WOOD RESEARCH Volume 63, Number 3, 2018
Vladimír Ihnát, Henrich Lübke, Albert Russ, Pažitný Andrej, and Vlastimil Borůvka

Waste agglomerated wood materials as a secondary raw material for chipboards and f ibreboards Part II. Preparation and characterisation of wood f ibres in terms of their reuse

The paper describes a process for the preparation of fibre from waste wood particleboards (PB), oriented strand chipboard (OSB) and medium density fibreboard (MDF). The purpose of recycling of agglomerated wood materials is to reuse them for the production of fibrous materials. The agglomerated materials disintegrated after the initial destruction were further processed under the specified conditions with respect to the moisture content, their type, adhesive used, and properties of final particles – wood chips. The obtained wood particles were characterized by the fractional composition of chips. The resulting chips were mechanically defibred with subsequent characterization of fiber obtained for its reuse in the manufacture of MDF. A quantity of formaldehyde released into the water when cooking waste MDF and PB was set up depending on the cooking time. Residual level of formaldehyde is the main chemical load that determines the amount of waste material that can be reused for production of new panels based on ureaformaldehyde adhesives.

WOOD RESEARCH Volume 63, Number 1, 2018
Balberčák Jozef, Boháček Štefan, Pažitný Andrej, Vladimír Ihnát, and Henrich Lübke

Chemical processing of waste wood based agglomerates Part II: Evaluation of properties of fluting liners made of semichemical pulp obtained by an alkaline cooking process

The article describes the method of evaluation and preparation of fluting liners produced from semichemical pulp obtained from waste wood particle boards (PB) and oriented strand boards (OSB). The semichemical pulp was obtained using an alkaline cooking process from a sorted fraction of the 4-8 mm chips. Properties as thickness, bulk density, air resistance of paper sheet, tensile strength, tensile index, breaking length, burst index, CMT30 and SCT were monitored on lab sheets 127 g. m-2 and 170 g. m-2. Values of pH and residual NaOH were determined in the batch leachate.

WOOD RESEARCH Volume 65, Number 5, 2020
Henrich Lübke, Vladimír Ihnát, Kuňa Vladimír, and Balberčák Jozef

A multi-stage cascade use of wood composite boards

A multi-stage cascade model was implemented on wood composite boards in four stages: particle boards → 100% recycling → middle density fibreboards → 100% recycling → paper liner. Preparation of composite boards bonded with urea-formaldehyde resin was simulated on plates 400 x 400 mm and final fiber was pulped using semi-production refiners to create the conditions closed to real. Mass changes and losses were observed during a whole simulated life process.
Results confirmed a deterioration of mechanical strength of recycled particle boards, the flexural strength in 13% and internal bond strength in 34% and slight increasing of the modulus of elasticity in static bending in 1.3%. Termomechanical pulping for the fineness in range 13°SR-24°SR (Schopper-Riegler) was chosen as appropriate for a fibrous board preparation from recycled chips, but their mechanical properties are at lowest levels compared to the requirements of standards. A low quality paper liner containing OCC, to improve its strength, was produced in the last stage of cascading.

WOOD RESEARCH Volume 65, Number 2, 2020
Vladimír Ihnát, Henrich Lübke, Balberčák Jozef, and Kuňa Vladimír

Size reduction downcycling of waste wood. Review

The article includes research related to utilization of waste wood which is primarily size reduced due to its voluminity for next processing for lower value added products for about last twenty years. Procedures and results obtained by different authors were considered in one study. In this review a wood waste downcycling was consider as a process of transformation of large size wood products over their lifetime to the new products, where a size reduction is one of the first operations needed to achieve to. Incineration of each way was excluded from the present review, but second-generation biofuels are considered as potential products for the future. Two points of research selection according to origin and according to products made of waste wood was applied in this review. Comparison shown that the most industrially applicable implementation of treated particles obtained from waste wood is intended to the composite materials production as particleboards, fibreboards, cement-bonded and wood-plastics.