Performance of medium-density particleboards from Eucalyptus grandis and Triticum aestivum treated with tall oil and citric acid

Particles of flooded gum (Eucalyptus grandis) were bonded using three bio-based adhesives - anhydrous citric acid (CA), tannin-citric acid (TCA) and ricinoleic acid (RA) - from renewable sources and hot pressed to produce medium density particleboard (MDP). The bonding capacity of such adhesives and properties of the MDP were evaluated and compared to the requirements of seven grades of particleboards, according to the EN 312 (2010) standard. The RA did not create adhesion reaction with the wood particles. Adhesives formulated with CA and TCA presented capacity to bond eucalyptus particles into MDP confirmed by esterification reactions of the FTIRS analysis. MDP bonded with CA met requirements as high as grade P5 of the EN 312 (2010) standard for static modulus of elasticity (MOE) and internal bond (IB) and P2 for modulus of rupture (MOR). Panels bonded with TCA met requirements up to grade P3 for MOE, however, did not withstand water absorption.

MDP (medium density particleboard) panels are normally graded in composition along their cross-section, using low-size particles and high concentration of adhesive on the particleboard surface (leading to improved physical and mechanical properties), and high-size particles in the particleboard core (interior), which provide higher porosity. Then, the aim of this study was to evaluate the impact of using different contents of bamboo particles in the particleboard core, on their physical and mechanical properties. The production of the panels was carried out using Pinusoocarpa (P) and Bambusavulgaris var. Vittata (B) particles in different contents (100% P, 100% B, 50% de B e 50% de P, 25% de B e 75% de P, 75% de B e 25% de P) in the core of the particleboards. The face of the particleboards were composed of P particles. The panels were produced with nominal density of 0.70 g/cm3, 40:60 face:core relation, 11% urea-formaldehyde adhesive in the faces and 8% adhesive for the core, specific pressure of 3.92 MPa, 160 °C temperature and pressing time of 8 min. After seasoning, the panels were submitted to evaluation of the thickness swelling (TS) and water absorption (WA) after 2 and 24 h of immersion, apparent density (AD), internal bonding (IB), modulus of rupture (MOR) and modulus of elasticity (MOE) under static bending. There was no statistical difference between the treatments for AD, IB, MOR and MOE values. Panels produced with high contents of bamboo particles (100% B, 75% B e 50% B) in the core, presented the lower WA and TS values, leading to improved dimensional stability than panels with only pinus particles. The present results show the important impact of using functionally gradation and bamboo particles on the physical properties of the MDP panels produced.

This study explores the effects of pre-drying time on the physical and mechanical properties of plywood bonded with citric acid (CA) and maleic acid (MA) adhesives. Plywood was constructed using Jabon wood veneers arranged into three layers with 30 x 30 x 0.6 cm dimensions. The adhesives were applied at a spread rate of 140 g/m2, and the boards were hot-pressed at 190 °C for 10 minutes under a pressure of 5 MPa. The pre-drying time of the veneers was 0 and 12 hours at 80 °C was utilized before hot pressing. Physical properties tested included density, moisture content (MC), water absorption (WA), and thickness swelling (TS). In contrast, the mechanical properties tested were modulus of elasticity (MOE), modulus of rupture (MOR), and tensile shear strength (TSS). The results showed that the pre-drying time significantly enhanced the mechanical properties, particularly for CA adhesive, which demonstrated higher MOE (66720 kg/cm2), MOR (265 kg/cm2), and TSS (7.09 kg/cm2). The density ranged from 0.43 to 0.49 g/cm³, MC from 5.92% to 9.70%, WA from 60.93% to 93.08%, and TS from 4.35 % to 7.07 %. The enhanced performance is attributed to chemical reactions during pre-drying, such as esterification, which improves bond strength and dimensional stability. These findings suggest that pre-drying time at 12 h combined with CA adhesive is an effective method to produce high-quality, eco-friendly plywood.

Oil palm trunk is an excellent raw material for thermally compressed wood board. However, improvements to dimensional stability during water absorption and reduced thickness swelling has been tied to losses in other mechanical properties, especially as the compression temperature is increased. Toward solving this trade-off, we analyzed the effects of a 48 h pre-soak in citric acid solutions (0, 5, 15, 25, or 35% w/v in distilled water) on the physical and mechanical properties of oil palm board compressed at 140 °C. The reference benchmark case was compressed at 200 °C without pretreatment. The oil palm board raw materials were obtained from outer, middle and inner parts of trunk. The results showed that the oven-dry density of compressed oil palm board made from different parts of trunk increased with thermal compression (maximum pressure 12.26 MPa for 8 min). The citric acid pretreatment improved water absorption and thickness swelling properties of oil palm board thermally compressed at 140 °C, consistent with the citric acid concentration. The carboxyl groups in citric acid cross-link with the hydroxyl groups in the wood. However, no significant difference was found between the benchmark (200 °C) and pretreatments with 5 or 15% citric acid. The citric acid altered the wood chemistry during hot compressing at 140 °C. Static bending strength, modulus of rupture (MOR), and modulus of elasticity (MOE) slightly decreased with the citric acid pretreatment, matching the effects of high temperature compression at 200 °C.

This study was done to investigate the effects of ozone treatment as a method to improve the properties of empty fruit bunch (EFB) medium density particleboard. Two types of EFB were used in this study i.e. screw pressed and non-screw pressed empty fruit bunch. These EFB were treated in an ozone chamber for 8 hours prior to particleboard manufacturing. The mechanical properties, Modulus of Elasticity (MOE), Modulus of Rupture (MOR) and Internal Bonding (IB) and physical properties, water Absorption (WA) and Thickness Swelling (TS) of EFB particleboard were determined. The results showed that the ozone treatment could increase the MOR and IB values of EFB particleboard, but had no significant effect on MOE values. For physical properties, the values showed no improvement for TS and WA. The panels manufactured using ozone treatment was found suitable for applications for furniture products.

The properties of oriented bamboo scrimber boards (OBSB) have been investigated at three density levels (0.8, 0.9, and 1.0 g cm3), while the boards were made from moso bamboo (Phyllostachys pubescens) grown in Taiwan (T-OBSB) and China (C-OBSB). A non-destructive technique (NDT), ultrasonic-wave velocity (Vu ) measurements were applied and the dynamic modulus of elasticity (MOEdyn) was calculated. Moreover, static modulus of elasticity (MOE), modulus of rupture (MOR), profile density distribution, internal bond strength (IB), springback (SB), and dimensional stability were determined based on traditional methods. Positive linear relationships between density and Vu , MOEdyn, MOE and MOR were observed, no matter if the measurements were done parallel (//) or perpendicular (⊥) to the fiber direction of the OBSBs. Moreover, Vu (//), MOEdyn,u(//), MOE(//), and MOR(//) were higher than Vu (⊥), MOEdyn,u(⊥), MOE(⊥) and MOR(⊥). C-OBSB had slightly lower Vu (//), Vu (⊥), MOEdyn,u(//) and DMOEu(⊥) values than T-OBSB. T-OBSB had higher MOE(//), MOE(⊥) and MOR(//) than C-OBSB, but less MOR(⊥). The profile density distribution of high-density T-OBSB showed singnificant data scattering. The profile density distribution of C-OBSB was homogeneous at all density levels. IB and SB data are directly proportional to density, but water absorption, thickness swelling and volumetric swelling are inversely proportional to density. T-OBSB has better bonding and strength properties, and dimensional stability than C-OBSB.

The aim of this research was to produce three-layer Medium Density Particleboard (MDP), with the addition of impregnated paper, in the inner layer, in proportions of 1; 5 and 20%. In this study, MDP was composed with particles of small size in outer layers, and larger particles in internal layer. After panel manufacturing, physical and mechanical tests based on Brazilian Code ABNT NBR 14.810 were carried out to determine moisture content; density; thickness swelling; water absorption; modulus of rupture (MOR) and modulus of elasticity (MOE) in static bending and internal adhesion. Test results were compared to commercial panels, produced with 100% Eucalyptus, considering the requirements specified by Brazilian Code. Properties presented values close to normative specifications, indicating positively the possibility of production of MDP using addition of waste paper impregnated.

Citric acid was utilized as a bonding agent in the production of Sembilang bamboo particleboard. The limitation in using bamboo for particleboard production is that the silica content in bamboo skin can accelerate particleboard processing machines' bluntness and reduce particle adherence in particleboard manufacturing. This research aimed to investigate the influence of bamboo skin and citric acid content on the characteristics of Sembilang bamboo particleboard. Particleboards were prepared using bamboo particles (type A) and unskinned bamboo particles (type B). The citric acid solution (59%) was sprayed over the surface of bamboo particles to obtain three different levels of citric acid, i.e., 15, 20, and 25 % (based on bamboo particles’ dry weight). The Sembilang bamboo particleboards were manufactured using a hot-pressing machine at 200°C, 5 MPa for 10 min. The particleboard targeted density was 0.8 g/cm3. The type B particleboards’ internal bond (IB), modulus of rupture (MOR), water absorption (WA), and thickness swelling (TS) were superior compared to the type A particleboards. This was influenced by the lower concentration of silica in type B particleboards, which tend to allow an intimate contact area among particles and citric acid then produced better quality particleboards compared to type A particleboards. The type B particleboards met the obligation of JIS A 5908 for type 18 particleboard in terms of modulus of rupture, modulus of elasticity, and internal bond, however, only fulfilled the type 8 particleboard in terms of screw holding power. The physical properties of Sembilang bamboo particleboard were also improved when using type B bamboo particles and adhered with citric acid at a level of 25%.

Pleurotus ostreatus (PO) is one of the edible mushrooms cultivated in baglog as the medium. Baglog’s productive age is around 4-5 weeks. The more PO produced, the amount of baglog waste also increases. The main component of baglog is wood sawdust, which contains lignocellulose; therefore, baglog has great potential to be used as a raw material for making particleboard. This research aims to make particleboard from baglog waste and determine the effect of the type and adhesive concentration on the physical and mechanical properties of the particleboard that is produced. Particleboard is made by mixing baglog waste, whose particle size is 40 mesh, with citric acid and sucrose adhesives whose concentrations are varied between 50%, 60%, and 70%. Furthermore, the particleboard was formed using a hot press machine (200 °C, 10 MPa) for 15 minutes. The obtained particleboard will be analyzed for its physical properties, including density, moisture content, water absorption, thickness swelling, morphology, and mechanical properties, including modulus of rupture (MOR) and modulus of elasticity (MOE). The test refers to the JIS A 5908-2003 type 8 standard. As a result, particleboard made using citric acid adhesive (citric acid 70%; C70) has a better physical and mechanical properties compared to sucrose adhesive, with a density value of 0.86 g/cm³, moisture content of 4.118%, thickness expansion of 3.992%, water absorption capacity of 36.89%, 13.456%, MOR 9.682 MPa, and MOE 1.455 GPa.

Cement-bonded particleboards of 6 mm in thickness were manufactured using maize stalk (Zea mays) particles of uniform sizes at three levels of board density and additive concentrations respectively. The bending strength and dimensional properties were assessed. Increase in board density and additive concentration caused increase in Modulus of rupture (MOR), Modulus of elasticity (MOE), and decrease in Thickness swelling (TS) and Water absorption (WA). The MOR, MOE and TS of the boards were significantly affected by board density except for WA, but additive concentration affected all the boards’ properties examined at p ≥ 0.05. Strong and dimensional stable cement-bonded boards could be manufactured from maize stalk particles with Portland cement as the binder after hot water treatment. Although the dimensional stability and mechanical strength properties of the boards were affected by the board density and additive concentration, the study revealed that cement-bonded particleboards could be manufactured from maize stalk (Zea mays) particles. However, the increase in board density and additive concentration could cause the increase in MOR and MOE, and cause the decrease in TS and WA of boards.

Crop residues used as lignocellulose materials for particleboards formulation

Medium-density particleboards from modified rice husks and soybean protein concentrate-based adhesives

Citric acid was utilized as a bonding agent in the production of Sembilang bamboo particleboard. The limitation in using bamboo for particleboard production is that the silica content in bamboo skin can accelerate particleboard processing machines' bluntness and reduce particle adherence in particleboard manufacturing. This research aimed to investigate the influence of bamboo skin and citric acid content on the characteristics of Sembilang bamboo particleboard. Particleboards were prepared using bamboo particles (type A) and unskinned bamboo particles (type B). The citric acid solution (59%) was sprayed over the surface of bamboo particles to obtain three different levels of citric acid, i.e., 15, 20, and 25 % (based on bamboo particles’ dry weight). The Sembilang bamboo particleboards were manufactured using a hot-pressing machine at 200°C, 5 MPa for 10 min. The particleboard targeted density was 0.8 g/cm3. The type B particleboards’ internal bond (IB), modulus of rupture (MOR), water absorption (WA), and thickness swelling (TS) were superior compared to the type A particleboards. This was influenced by the lower concentration of silica in type B particleboards, which tend to allow an intimate contact area among particles and citric acid then produced better quality particleboards compared to type A particleboards. The type B particleboards met the obligation of JIS A 5908 for type 18 particleboard in terms of modulus of rupture, modulus of elasticity, and internal bond, however, only fulfilled the type 8 particleboard in terms of screw holding power.

This study aimed to evaluate the effect of mixing Acrocarpus fraxinifolius particles with Pinus oocarpa particles for the production of medium-density particleboard (MDP). The three-layer MDPs (20/60/20) were produced at five different levels of Acrocarpus fraxinifolius particle content (0, 25, 50, 75, and 100%) in association with Pinus wood. The adhesive urea-formaldehyde was applied in amount 11% in the faces and 7% in the core, based on the dry mass of particles. The mixture of particles and adhesive was placed in molds (50 x 50 x 1.5 cm) and hot-pressed under a pressure of 3.92 MPa and 160 °C of temperature for 8 minutes. Properties of panels such as density, modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB), water absorption (2 and 24h), and thickness swelling (2 and 24h) were evaluated. There were no statistical differences between the densities of the particleboards. The contents 25 to 100% of Acrocarpus fraxinifolius obtained improvement in mechanical properties. The MDP 100% Acrocarpus showed potential for some higher value uses, such as in dump environments. However, until more testing is done, these panels are only recommended for dry-use applications. Using Acrocarpus fraxinifolius in combination with Pinus wood, or even using only Acrocarpus fraxinifolius wood is suitable for the production of MDP.

Sugarcane bagasse can be used in the manufacture of panels for the furniture industry, but has a high water absorption compared to wood panels. Thus, this raw material needs heat treatment to reduce the hygroscopicity of the panels. The aim of this study was to evaluate the effect of different levels of heat treatment temperature on the particleboard properties made from sugarcane bagasse. The experiment consisted of four treatments, being evaluated three temperatures heat treatment of sugarcane bagasse (170, 200 and 230 °C) and without thermal modification treatment (Control). The particles were evaluated for their anatomical, chemical and physical characteristics. The panels were produced with nominal density of 0.70 g/cm3, relation face/core of 40:60, 11% urea–formaldehyde adhesive to the faces and 7% of adhesive to the core, pressing cycle of 160 °C temperature, pressure 3.94 MPa and for a period of 8 min. The panels were evaluated for its physical properties density, compression ratio, moisture, water absorption and thickness swelling after 2 and 24 h of immersion; their mechanical properties internal bond and modulus of rupture and modulus of elasticity at bending. The heat treatment of the bagasse particles at 230 °C promoted significant improvements in the quality of particleboard, resulting in decreased of the water absorption and thickness swelling values of the panels and increase in modulus of elasticity values, and allowing meet marketing standards regarding the thickness swelling after 24 h of immersion in water. Which demonstrates the great potential of using the heat treatment temperature of 230 °C for the production of particleboard with sugarcane bagasse.