Structural, physical and mechanical changes of cement-bonded particleboards during sudden fluctuations in temperature and moisture

The paper presents research focused on behaviour of cement-bonded particleboards with modified composition during sudden changes of temperature and humidity. Four types of boards were made—one control and three modified ones. Finely ground limestone was used as a modifying component in binder. Secondary wood particles made from crushing cuttings of cement-bonded particleboards were used as chips substituent. Two sets of test specimens (1 set = 6 test specimens) were manufactured. The first set was stored in laboratory conditions. The second set was subjected to 10 cycles of sudden changes of temperature (− 20 °C to + 70 °C) and humidity in accordance with EN 321 (further in the paper referred to as “wet–frost–dry cycle”.) After each cycle, dimensions and mass of the test specimens as well as ultrasonic pulse velocity were determined. A detailed analysis of structural changes in boards during cycling was carried out by an optical microscope. After 10 wet–frost–dry cycles were completed, bending strength and modulus of elasticity in bending were determined. The analysis of test results implies a very good relation between change of ultrasonic pulse velocity and width of cracks in the area of interfacial zone between cement matrix and wood particles. This finding also corresponds with dimensional and volumetric changes of the boards. Dependence of bending strength and modulus of elasticity in bending on composition of boards is apparent. Positive influence of secondary spruce chips on dimensional changes of cement-bonded particleboards caused by sudden changes of temperature and humidity was proved. Finely ground limestone contributes to more resistant structure of boards which leads to improved bending properties. Adverse conditions had more considerable influence on bending strength (decrease by 21% to 26%) than on modulus of elasticity in bending (decrease by 12% to 19%).

Compression strength-focused properties of wood composites induced by structure

Compression strength-focused properties of wood composites induced by structure. The aim of the following study was to examine the contractual compression strength and modulus of elasticity when compressing (MOEC) of three different wood composites with various structure types: softwood (coniferous) plywood, OSB and laminated particleboard 24 mm thick. The biggest MOEC value was performed by the particleboard laminated 24 mm MOEC equalling 70.00 N/mm2. The second was found by the OSB panels, equalling 63.03 N/mm2. Last, but with MOEC value close to OSB, was softwood plywood with MOEC of 62.44 N/mm2. The lowest compression strength was observed by OSB samples, with a value of 2.75 N/mm2. The second lowest value has been performed by coniferous plywood (2.80 N/mm2). The highest compression strength occurred by the particleboard laminated 24 mm, equalling 3.31 N/mm2. Density shares and density profiles of the samples were also analysed, all of the examined composites performed U-shaped density profile The results of the study showed that there is no significant correlation between density and obtained parameters under compression. Observation of density share let the Authors conclude conversely than the results showed. It is supposed that the key factor affecting the compression performance of samples was the adhesive area and solid glue content within the composites. It is assumed that the bigger total contact surface of wood particles coated with adhesive resin, so the sum of the effective (gluing particles) surfaces of the adhesive joint is the better mechanical properties can be performed. This is why the laminated particleboard gave the best mechanical properties, while the worst were observed by the softwood plywood.

Sodium Iodide as a Contrast Agent for X-ray Micro-CT of a Wood Plastic Composite

The properties of wood plastic composites (WPCs) depend on their microstructure, particularly the level and geometry of wood reinforcement in the composite. We hypothesize that impregnating a WPC with a radiocontrast agent will increase the contrast between wood and plastic, allowing better visualization of its microstructure and numerical analysis of the geometry of its wood reinforcement. A commercial WPC was scanned using X-ray micro-CT, impregnated with aqueous sodium iodide, and then rescanned. CT data from both scans were visualized, and we analyzed the geometry of wood reinforcement and levels of wood, plastic, zinc borate (ZB), and voids in the WPC. ZB occurred mainly as discrete particles between wood flakes, and interfacial voids formed a network of cracks within the WPC. Sodium iodide labeling made it possible to clearly visualize wood and plastic in the WPC and quantify levels of different phases and the geometry of wood particles. However, sodium iodide was not an ideal contrast agent because it swelled wood particles, closed interfacial voids, and partially dissolved ZB particles. We suggest methods of overcoming these limitations and conclude that advances in labeling are necessary to improve our understanding of the relationship between the microstructure of WPCs and their properties.

Characterisation of Wood Particles Used in the Particleboard Production as a Function of Their Moisture Content

The properties of particleboards and the course of their manufacturing process depend on the characteristics of wood particles, their degree of fineness, geometry, and moisture content. This research work aims to investigate the physical properties of wood particles used in the particleboard production in dependence on their moisture content. Two types of particles currently used in the production of three-layer particleboards, i.e., microparticles (MP) for the outer layers of particleboards and particles for the core layers (PCL), were used in the study. The particles with a moisture content of 0.55%, 3.5%, 7%, 10%, 15%, and 20% were tested for their poured bulk density (ρp), tapped bulk density (ρt), compression ratio (k), angle of repose (αR), and slippery angle of repose (αs). It was found that irrespective of the fineness of the particles, an increase in their moisture content caused an increase in the angle of repose and slippery angle of repose and an increase in poured and tapped bulk density, while for PCL, the biggest changes in bulk density occurred in the range up to 15% of moisture content, and for MP in the range above 7% of moisture content, respectively. An increase in the moisture content of PCL in the range studied results in a significant increase in the compression ratio from 47.1% to 66.7%. The compression ratio of MP increases only up to 15% of their moisture content—a change of value from 47.1% to 58.7%.

On the Effect of the Distances between Coal and Wood Particles during Their Joint Pyrolysis on Sulfur Oxides Formation

The simultaneous pyrolysis of coal with wood was experimentally found to allow reducing concentrations of sulfur-containing substances in gases released. The objective of experimental studies is comparison of the sulphate of calcium and aluminum in the ash of coal-wood mixtures after pyrolysis of the latter in a dense “packing” of aggregate particles of these two fuels and at a few millimeters distance between particles. The 3B-grade lignite, T-grade bituminous coal and pinewood sawmill waste were chosen as feedstocks for pyrolysis experiments because they are widespread in Russia as well as many other countries. The elemental composition of all raw materials and pyrolysis residues was determined. The inorganic composition of obtained pyrolysis product in the solid phase was characterized by X-ray analysis. The content of aluminum and calcium sulfate in residue in case of simultaneous processing of coal with wood was found to be higher, compared to the processing of coal only (within the random errors of the experiment), than those established for such mixtures under conditions of dense “packing” of large masses (up to 15 g).

Mechanical Properties of Particleboard using Acacia Mangium Wood Particles Binded With Seaweed-Based Adhesives

The purpose of this study was to evaluate the mechanical properties of particleboards made from Acacia mangium wood particles binded with three different types of seaweed-based adhesive. Red seaweed (RS), brown seaweed (BS) and green seaweed (GS) were used as the seaweed-based adhesives., while particleboard using urea formaldehyde (UF) adhesive was produced as control. Adhesives and wood particles were mixed and then undergone mat-forming, pre-pressing, hot-pressing and conditioning process. The test pieces for bending test (Modulus of Elasticity, MOE; Modulus of Rupture, MOR), and internal bonding strength (IB) were cut into size according to JIS A 5908: 2003. From mechanical properties results attained, for internal bonding strength test, all boards using RS, BS and GS adhesives were found to be significantly different at p≤0.05. Apart from that, RS adhesive showed highest MOE and MOR at 529.4259 N/mm2 and 1.7900 N/mm2, respectively. As a conclusion, the mechanical properties of particleboard using RS, BS, and GS adhesives showed RS stands out as the better adhesive among them which have significant effects on its strength.

Investigation of Furfural Formation and Mechanical Properties of Suberinic Acids-Bonded Particleboards Depending on their Preparation Parameters

Silver birch (Betula pendula) outer bark suberin can be used as a raw material to make an adhesive for particleboards (PBs). It is a promising formaldehyde-free alternative to traditional synthetic resins. However, the adhesive is acidic, which can catalyse furfural (FUR) formation from xylans in wood particles that are used for the preparation of PBs. FUR being a volatile organic compound can be emitted from the PBs and exposure to it can have harmful effects on humans. In the scope of this study, the effects on technological parameters (wet adhesive pH: 3, 6 and 9), glycerol as an additive to adhesive and hot-pressing temperature (180...230 °C) were investigated on the FUR formation in PBs. The FUR content was determined with high-performance liquid chromatography-ultraviolet spectroscopy system from the extracts of milled PBs. Mechanical properties (modulus of elasticity, bending strength, and thickness swelling) of the PBs were also studied. When using an adhesive with a pH 6 at hot-pressing temperature 230 °C with no glycerol added, it was possible to obtain PBs that satisfied the requirements of EN 312 P2 (boards for interior fitments). The FUR yield of these boards were more than 6 times lower than for the PBs pressed at 230 °C with a wet adhesive pH value 3.

Dimensional stability and mechanical properties of bio-based composites produced from hydro-thermal treated wheat straw

Bio-composites were produced from untreated (UT) and hydro-thermally treated (HTT) wheat straw (WS) particles and wood, and their dimensional stability and mechanical properties were investigated. The HTT treatment consisted of subjecting the WS particles to a steam explosion process for 8 min at 180 °C. The HTT and UT WS particles were mixed with the wood particles at 10, 20, 30, and 40% ratios. The physical properties, including density, water absorption (WA), and thickness swelling (TS), were determined for the bio-based composites. The mechanical properties evaluated included the modulus of rupture, modulus of elasticity, and internal bond strength. Statistical analyses showed that the hydro-thermal treatment and the WS ratio had significant effects on the dimensional stability and mechanical properties of the bio-composites. The WA of the composites after 2-h and 24-h rose significantly when the HTT WS particle ratio was increased from 10 to 40%. The 2-h and 24-h WA values of HTT-10 were 6.3% and 5.3% lower than those of UT-10, respectively. Improvements in the 2-h TS value were achieved by the HTT WS particles at the 10% ratio, and in the 24-h TS value at the 10 and 40% ratios. The mechanical properties of the composites were higher in the HTT group, but decreased in both the UT and HTT groups as the WS ratio increased.

Alkali-treated wheat gluten cross-linked with sodium alginate as a bio-based wood adhesive for interior grade particleboard

A bio-based wood adhesive formulation free of formaldehyde and made from alkali-treated wheat gluten (WG) and sodium alginate (SA) was developed. Its formulation was optimised, and it was characterised by Fourier Transform Infrared (FT-IR) spectroscopy. The bio-adhesive was utilized to make particleboards both with virgin wood particles and recycled wood particles. A dry bio-adhesive content of 35% (w/w) was used to make samples with both type of particles. Single-layer samples of 10 mm thickness were obtained using wood particles of 1 mm (both virgin and recycled). These samples then were subjected to 3-point bending tests. Whereas the bending strength of samples made with recycled wood particles was 18.09 N/m2 and therefore satisfied Type 18 of the Japanese industrial standards (JIS A 5908:2015), the bending strength of the samples made with virgin wood particles was 8.08 N/m2 and satisfied ‘Type 8 Base particleboard Decorative particleboard’ of the Japanese standards. The density of particleboard samples made from recycled wood particles was 916 kg/m3, while that of samples made from virgin wood particles was 732 kg/m3. The alkali-treated WG and SA bio-adhesive has the potential to be used to re-manufacture particleboards, which can then be recycled and not disposed in landfills.