In this study, the effects of three different particle sizes of wood wastes (A = –8 + 12 mesh; B = –12 + 20 mesh; C = –20 + 30 mesh) and factory shavings (D) on the properties of particleboard were investigated. According to the test results, three-layer particleboard was designed. Particleboard face layers made with mixture of A, B, and C. The core layer made with D. The ratio of core layer to face layers is 50:50. Three-layer particleboard were fabricated with 12% urea-formaldehyde (UF) resins and three different high voltage electrostatic field intensities (0 kv, 30 kv, 60 kv). The internal bond (IB) strength, modulus of rupture (MOR), modulus of elasticity (MOE), thickness swelling (TS), and water absorption (WA) of particleboard were evaluated. The density distribution of the three-layer particleboard were examined by vertical density profiles (VDP), and the bonding mechanism and functional groups changes in the particles were analyzed by FTIR analysis. The results showed that HVEF treatment intensity play a remarkable role in properties of particleboard. The particleboard with higher electrostatic field intensities treatment has higher MOE, MOR, IB, and TS. Under HVEF treatment (60 kv), the MOR, modulus of MOE, and IB of three-layer particleboard were 23.61 N/mm2, 2787.09 N/mm2, and 0.86 N/mm2, respectively. FTIR indicated that the surface activity of wood particles was increased electric field treatment.
As the three basic building materials, Wood products are easy to be processed into different shapes and sizes of materials, widely applied in furniture, decoration and construction industries. In recent years, timber resources are increasingly scarce, and timber supply and demand are contradictory. The efficient use of wood pellets can minimize production costs and reduce the adverse environmental impact of waste [
Particleboard manufactured from wood particles or other wood fiber material scraps and synthetic adhesives can be extensively used in buildings, furniture and cabinets. It can convert relatively useless, small-sized, or low-grade wood particles into useful large boards [
The mechanical, physical, and surface properties of particleboard are important indicators for evaluating its quality [
The geometry structure of wood particle has a significant effect on the properties of particleboard [
Studies have shown that the high voltage electrostatic field (HVEF) has a positive impact on the surface properties of many materials, and it is applied to the processing and preparation of materials [
This paper was to study the effect of HVEF treatment on the properties of the particleboard. In the first step, particleboard was manufactured by wood particles of different sizes (A, B, C) and shavings (D), modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB) values were tested. In the second step, the MOE of particleboard with different mixture ratios was predicted by using obtained data. In the third step, according to the predicted results, three-layer particleboard was designed. In the fourth step, the effect of HVEF treatment intensities (0 kv, 30 kv, 60 kv) on the important physical properties and mechanical properties of the particleboard was studied.
The wood particles are sourced from the factory, and the particles obtained were classified using a vibrating machine and sieves of 8 mesh (2.36 mm), 12 mesh (1.70 mm), 20 mesh (0.850 mm), 30 mesh (0.60 mm). Classified into three sizes (A = –8 + 12 mesh; B = –12 + 20 mesh; C = –20 + 30 mesh). Shavings (D = 3 mm−9 mm) come from a furniture factory. The shavings and particles were dried in a blast drying oven at a drying temperature of 103°C to reduce the moisture content of the wood particles to less than 5%. Urea-formaldehyde (UF) adhesive solid content was 50%, with a formaldehyde/urea (F/U) ratio of 1.4, and viscosity of UF 0.37 Pa.s. Ammonium chloride (0.5%) was added to the resin as a curing agent. No water-repellent chemicals are added to the particleboard.
The manufacturing steps of HVEF treated particleboard are shown in
The particleboard with dimensions of 400 mm × 400 mm × 10 mm (length × width × height). The particles/shavings were placed in a blender and sprayed with the 12% resin adhesive. Particles with adhesive was taken to a mold with 400 mm × 400 mm × 10 mm. The particles were pre-pressed before hot pressing to consolidate the loose particle. Particleboard were pressed under 2.5 N/mm2 pressure, at 160°C, for 8 min, the target density of the particleboard design was 700 kg/m3.
Twelve types of particleboards, with a total of 36 particleboards, were fabricated (
Particleboard types | Particle size (mesh) | Shavings | Intensity (kv) | ||
---|---|---|---|---|---|
-8 + 12 | -12 + 20 | -20 + 30 | |||
A1 | 100% | 0 | |||
B1 | 100% | 0 | |||
C1 | 100% | 0 | |||
D1 | 100% | 0 | |||
A2 | 100% | 30 | |||
B2 | 100% | 30 | |||
C2 | 100% | 30 | |||
D2 | 100% | 30 | |||
A3 | 100% | 60 | |||
B3 | 100% | 60 | |||
C3 | 100% | 60 | |||
D3 | 100% | 60 |
The composite modulus assumption for the particleboard specimens is only affected by the physical and mechanical properties of the selected wood, resin, and air. The distribution of elastic constants and strength index parameters along the main axis of the thickness direction depends on the properties of the wood, the properties of the adhesive, and the penetration distribution of the adhesive at the interface form. The specific factors include: 1) The elastic modulus of wood particles, 2) The elastic modulus of resin, 3) The geometry shape of the particles 4) The shear modulus of wood particles. The effects of the vertical density gradient, uniformity, and resin compatibility were not considered in the model. Adhesives are idealized non-void matrix materials, and the stress-strain relationship can be calculated using a continuous function.
The relationship between the material stiffness
The volume fraction of each component is of great significance to the application of the micromechanical compound theory. The volume of the resin cannot be measured directly. The volume fraction of the resin is calculated by dividing the volume of the resin by the target volume of each manufactured panel. Assume that the resin does not penetrate into the wood chips.
According to the laminated plate theory [
After analyzing the results of the uniform density particleboards and the prediction results of MOE, three-layer boards were designed. The Ratio was chosen based on the estimation values of MOE, the surface thickness to a core thickness of 50:50. The ratio of the mixture of A, B, C were 40:40:20. The structural design of the three-layer particleboard is as follows (
Three-layer particleboard manufacturing process, the mixture of A, B, C were placed on the face layers. D were placed in the core layer. The other processes are the same as the uniform particleboard. Three types of HVEF treatment intensities with a total of 9 particleboards were fabricated (
Particleboard types | Resign content (%) | Intensity (kv) |
---|---|---|
M1 | 12 | 0 |
M2 | 12 | 30 |
M3 | 12 | 60 |
All test specimens be conditioned to constant mass in a conditioning room with a relative humidity (RH) of 65% and a temperature of 20°C. After reaching a constant weight, use a circular saw to trim the panel, remove 10 mm from each side, select 5 samples per panel to determine the modulus of rupture (MOR), modulus of elasticity (MOE), according to EN 310 [
Cross-sectional density profiles were measured by X densitometer (EWS, Germany) with scanning speed of 0.5 mm·s-1.
ATR-FTIR spectroscopic measurements of the particleboards treat with 0 kv, 30 kv and 60 kv were performed using a Fourier transform infrared spectroscopy (FTIR, VERTEX 80V). The spectra were measured on 5 different spots (16 scans per spot) of the coated samples, at a wavelength range from 500 cm−1 to 4000 cm−1 and a resolution of 2 cm−1.
As shown in
Particleboard types | Density (kg/m3) | MC (%) | TS 24 h (%) | WA 24 h (%) |
---|---|---|---|---|
A1 | 672(3) | 9.69(0.36) | 27.24(1.03) | 65.14(2.41) |
B1 | 679(5) | 9.71(0.27) | 24.15(0.88) | 69.16(2.57) |
C1 | 675(4) | 9.73(0.46) | 19.04(0.73) | 71.32(2.76) |
D1 | 680(3) | 9.65(0.38) | 20.68(0.79) | 67.56(2.63) |
A2 | 676(4) | 9.74(0.47) | 25.03(0.87) | 58.39(2.04) |
B2 | 669(3) | 9.83(0.50) | 20.94(0.76) | 64.01(2.21) |
C2 | 681(4) | 9.68(0.34) | 17.56(0.61) | 64.90(2.45) |
D2 | 677(3) | 9.81(0.40) | 18.01(0.68) | 59.42(2.19) |
A3 | 680(2) | 9.84(0.43) | 22.18(0.72) | 53.62(1.79) |
B3 | 682(3) | 9.91(0.31) | 19.11(0.61) | 59.83(1.81) |
C3 | 690(1) | 9.74(0.55) | 14.62(0.46) | 60.58(1.92) |
D3 | 688(2) | 9.89(0.67) | 15.03(0.53) | 54.18(1.70) |
Note: Numbers in the parenthesis are standard deviations. MC: Moisture Content, WA: Water Absorption, TS: Thickness Swelling.
From
In research by Bodig and Jayne, wood composites are considered to be isotropic [
The relationship between the surface thickness and MOE was calculated by using the laminate theory and MATLAB calculation method. As shown in
Under the HVEF treatment, the elastic constants of the face layer, core layer, and urea-formaldehyde resin are shown in
Face layer | 2.4 | 2.4 | 0.29 | 0.30 |
Core layer | 1.8 | 1.8 | 0.45 | 0.30 |
UF | 7.8 | 7.8 | 7.3 | 0.44 |
MOE values of particleboard were predicted according to MTALAB, the predicted value was compared with the measured value, as shown in
Particleboard types | MOE value (N/mm2) | Relative error | |
---|---|---|---|
Experimental results | Modeling results | ||
M1 | 2315 | 2037 | 13.7% |
M2 | 2542 | 2315 | 14.9% |
M3 | 2787 | 2386 | 16.8% |
Besides, the estimation values of MOE and MOR are lower than the measured values. This change is due to not considering the particle board in the preparation of thermal stress and humidity. These factors can affect particleboard interface performance and mechanical performance [
The thickness swelling and water absorption of the panels are listed in
Particle-board types | Density(kg/m3) | MC (%) | MOR (N/mm2) | MOE (N/mm2) | IB (N/mm2) | TS 2hrs (%) | TS 24hrs (%) | WA 2hrs (%) | WA 24hrs (%) |
---|---|---|---|---|---|---|---|---|---|
M1 | 683(3) | 9.70 (0.41) | 19.40 (0.40) | 2265 (137) | 0.68 (0.03) | 14.7 (0.52) | 17.9 (0.62) | 61.4 (2.13) | 65.5 (2.32) |
M2 | 691(2) | 9.87 (0.37) | 21.72 (0.46) | 2542 (132) | 0.78 (0.04) | 13.6 (0.48) | 16.3 (0.58) | 53.9 (1.79) | 57.6 (2.06) |
M3 | 693(4) | 9.92 (0.42) | 23.61 (0.43) | 2787 (142) | 0.86 (0.04) | 12.5 (0.41) | 15.0 (0.52) | 47.7 (1.61) | 51.2 (1.77) |
Note: Numbers in the parenthesis are standard deviations.
Particleboard types | Mean maximum density (lower face layer) (kg/m3) | Mean minimal |
Mean maximum |
Mean panel |
---|---|---|---|---|
M1 | 737 | 639 | 741 | 683 |
M2 | 761 | 634 | 755 | 691 |
M3 | 782 | 628 | 769 | 693 |
For three-layer particleboard, the surface layer of the particleboard bears most of the load in the bending process, the higher the density of the surface layer, the better the mechanical properties, especially the bending properties [
The effect of high voltage electric field on chemical groups on the surface of three-layer particleboard was characterized by FTIR, and the results are shown in
In this study, the elastic modulus was predicted by using MATLAB software. The accuracy of prediction is more than 80%. According to the prediction results, three-layer particleboards are successfully manufactured from wood particles and shavings by optimizing the technological parameters, which proved to be a promising method. Properties of particleboard were evaluated. With the increase of electric field intensity, the properties of particleboard were improved, especially, and IB increased most significantly. The IB improvement was 25.6% under HVEF treatment (60 KV). This effect is attributed to the increase of polarization and crosslinking degree of UF resin and the preferable wettability of wood particles. Under HVEF treatment (60 kV), the MOR, MOE, and IB of three-layer particleboard were 23.61 N/mm2, 2787.09 N/mm2, and 0.86 N/mm2. With HVEF treatment intensities increased, the face layers were more compacted. The properties of three-layer particleboard meet the requirements of MOE, MOR, and IB in EN312 standard.
All authors contributed equally to this work.