Properties of particleboard produced using a sealed press

In this study, different properties of experimental particleboard produced using a sealed press were determined and were compared with those for particleboard produced using a conventional press. Three types of binder, namely urea formaldehyde (UF), melamine formaldehyde (MUF), and polymethylene diphenyl diisocyanate (PMDI), were used for board production. For the UF-bonded boards produced using the sealed press, the modulus of rupture and the internal bond strength (IB) decreased due to the high temperature and steam pressure used in comparison to the conditions in a conventional press. However, MUF- and PMDI-bonded boards had improved IB and thickness swelling (TS). For the PMDI-bonded boards, especially, the TS was further improved and IB was increased by using a sealed press. PMDI is known to possess superior properties and was confirmed to achieve good properties when used as a binder for particleboards produced using a sealed press.     

Effects of air injection on properties of particleboard manufactured using a radio-frequency hot press

The effectiveness of air injection for preventing the blowout of particleboards manufactured using a radio-frequency hot press was investigated by evaluating the board properties under artificially created conditions that were conducive to blowout. For evaluation, 10-mm-thick boards with densities of 0.7 and 0.8 g/cm³ and 20-mm-thick boards with a density of 0.7 g/cm³ were manufactured. Pressing times for the 10-mm-thick boards were 2, 4, 6, and 8 min, and those for the 20-mm-thick boards were 4, 6, 8, and 10 min. Without air injection, blowout occurred in all manufactured boards. With air injection, however, blowout did not occur in the 10-mm-thick boards with a density of 0.7 g/cm³. Moreover, air injection prevented blowout even when the board density and board thickness were increased to 0.8 g/cm³ (for 10-mm-thick boards) and 20 mm (the density was kept at 0.7 g/cm³), respectively. Air-injection radio-frequency pressing reduced the pressing time from 4 to 2 min for 10-mm-thick boards, and from 6 to 4 min for 20-mm-thick boards. Moreover, this reduction in the pressing time was achieved without a large reduction in the internal bond strength of the boards.     

Effects of mat moisture content and press closing speed on the formation of density profile and properties of particleboard

Isocyanate resin-bonded 0.5 and 0.7 g/cm³ lauan (Shorea sp.) particleboards were produced from mats with uniform and distributed moisture content (MC) distributions, using three hot press closing speeds. The effects of these processing variables on the formation of density profile in particleboard and board properties were analyzed statistically. A definition of the density profile was introduced, and the correlations among the various defining factors were established. The results are summarized as follows. (1) The peak density (PD) of particleboard could be increased, with a slight reduction in the core density (CD), using mats with different MC distributions. (2) In a conventional density profile, CD and PD are highly dependent on the board mean density (MD); and the gradient factor (GF), peak distance from the faces (Pdi), and peak base (Pb) are significantly correlated to each other, at the 99% significance level. (3) Greater press closing speed reduces Pdi and Pb, with an increase in GF. (4) Greater press closing speed could increase the PD in board of low MD, with minimal effect on CD. (5) The modulus of elasticity (MOE) of particleboards from mats with high MC near the faces were consistently higher than those from mats with uniform MC, irrespective of the press closing speed, whereas their modulus of rupture (MOR) became indifferent at higher MD under slow and fast closing speeds. (6) Sanding does not improve the MOR and MOE of particleboard significantly.     

Development of an air-injection press for preventing blowout of particleboard I: effects of an air-injection press on board properties

An air-injection press was developed to prevent particleboard from blowing out during the manufacturing process. The air-injection press, which has holes punched in the heating plates, injects high-pressure air into the board through the holes of one plate and releases the air through the holes of the other plate. The high-pressure air forces out vapor trapped within the board, thus preventing blowout. The newly developed press reduced the pressing time required for manufacturing board from high-moisture-content particles. However, the manufactured boards exhibited mechanical properties and dimensional stability inferior to conventionally manufactured boards.     

Effects of press closing time on mat consolidation behavior during hot pressing and on linear expansion of particleboard

Mat consolidation behavior was investigated at various press closing times (PCTs) using hinoki (Japanese cypress) particle mats. The temperature in the core layer of the mat, press pressure, and platen distance were measured. At the plateau stage during hot pressing, the core temperature decreased with increasing PCT. The core temperature did not increase before the platen distance equaled the target board thickness in the PCT range of 4–50 s and rose slightly when the PCT exceeded 100s. There was a linear relation between the logarithm of PCT and the maximum press pressure. The density profile across board thickness was strongly affected by the PCT. As the PCT increased, the position of the peak density (PD) moved toward the core layer as the PD itself decreased. The effect of PCT on the linear expansion (LE) of the board is discussed in relation to the density profile. There was no difference in LE after high relative humidity treatment in the PCT range 4–50s. LE appeared to be related to the low density and the precured region of the board surface. The LE after drying treatment was around –0.1%, and the thickness swelling after high relative humidity and drying treatments increased with increasing PCT.Part of this report was presented at the 51st Annual Meeting of the Japan Wood Research Society, Tokyo, April 1988     

Properties of particleboard manufactured using an air-injection radio-frequency hot press

A hot press was used to manufacture particleboards (H boards). A radio-frequency hot press (for RH boards) and an air-injection radio-frequency hot press (for ARH board) were also used, and the effects of air injection on preventing blowout and board properties were analyzed. The thicknesses and densities of manufactured boards were 10 and 30 mm, and 0.6, 0.7, and 0.8 g/cm³, respectively. The investigation ascertained the effects of air injection in preventing blowout when a radio-frequency hot press is used. The increasing order of temperature was ARH board > RH board > H board during the final pressing stage. For the 30-mm-thick boards, the temperature of H board increased to 100 °C and remained constant at 100 °C even when the pressing time was extended. The temperature of the RH board increased to 100 °C more quickly than in the case of the H board and remained constant at 110–118 °C. The temperature of the ARH board increased linearly to 130–142 °C. For both the 10- and 30-mm-thick boards, the internal bond strength of the RH board was almost the same as that of the ARH board at densities of 0.6 and 0.7 g/cm³. In contrast, the internal bond strength of the RH board was lower than that of the ARH board at a density of 0.8 g/cm³. For the 10-mm-thick boards, the thickness swelling in the RH board was almost the same as that in the ARH board irrespective of the density. However, for the 30-mm-thick boards, the thickness swelling in the RH board was higher than that in the ARH board. The low plasticization of particles due to air injection presumably results in a high degree of thickness swelling.     

Blowout conditions and properties of isocyanate resin bonded particleboard manufactured from high-moisture particles using an air-injection press

Blowouts of particleboards were artificially induced by increasing the vapor pressure inside the boards. Isocyanate resin bonded boards were manufactured from high-moisture particles, and the blowouts and board properties were analyzed. Boards with a high resin content of 5 % showed high bonding strength and did not blow out when pressed at 190 °C, but blew out at a raised temperature of 210 °C to increase vapor pressure inside the boards, thereby showing that blowout occurred when vapor pressure inside the boards exceeded the bonding strength of isocyanate resin. Boards with a low resin content of 2.5 % had low bonding strength and blew out when manufactured without air injection, but were successfully manufactured with air injection that prevents blowouts. However, the injection of high-pressure air reduced the strength properties of the board and increased the coefficient of variation, likely due to the discharge of isocyanate resin from the boards. Therefore, very small local blowouts occurred inside the boards, which lowered the strength properties of some specimens and led to a large coefficient of variation. When the pressure of injected air was lowered, the strength properties increased and the coefficient of variation decreased. This was possibly because the low-pressure air allowed isocyanate resin to remain in the boards, resulting in virtually no parts showing very low-strength properties.     

Effect of buffers on gypsum particleboard properties

The paper recounts how buffers affect the physical and mechanical properties of gypsum particleboard (GPB) and the initial curing time (IC) of gypsum. The acidic buffers were better than alkaline buffers for prolonging the IC of gypsum and affecting the properties of GPB. Weak acids were advantageous for curing gypsum. When suitable amounts of citric acid and trisodium citrate were added, high performances could be achieved and the IC of gypsum could be prolonged to about 2h. When alkaline buffers such as sodium carbonate were added, the 1C of gypsum was still short but the internal bond strength (IB), modulus of elasticity (MOE), and modulus of rupture (MOR) of GPB were obviously decreased. Citric acid was the best among the four buffers used; and the GPB had a good IB, MOE, MOR, and adequate IC when citric acid of 0.1% was added. Sodium carbonate was not suitable owing to low performance and short IC. Gypsum curing is an endothermic reaction.Part of this paper was presented at the 11th Annual Meeting of the Chugoko Skikoku Branch of the Japan Wood Research Society, Matsue, September 1999     

Effects of water soaking and outdoor exposure on nail joint properties of particleboard

Phenol-formaldehyde resin-bonded particleboard (PF board) and isocyanate resin-bonded particleboard (MDI board) were soaked in water at 40, 70 and 100 °C, and the relationships between soaking conditions and nail joint properties were analyzed. The soaking time to reach the lower limit of nail-head pull-through (NHPT) of the PF board was 2 h at 100 °C, while it took 168 h at 70 °C. The soaking time to reach the lower limit of lateral nail resistance (LNR) of the PF board was 24 h at 100 °C, but it did not take 168 h at 70 °C to reach it. The lower limits of NHPT and LNR for the MDI board were higher than those for the PF board. For the PF board, there was a high correlation between modulus of rupture, internal bond strength and nail joint properties. Based on the results of water soaking and outdoor exposure, it was shown that thickness change has a significant effect on NHPT and LNR, and that the reduction in NHPT and LNR results from the collapse of bonding points owing to swelling of the board.     

刨花板抗静电性能的研究

通过全电流充放电法，测得在刨花施胶过程中施加不同种类和数量的抗静电添加剂时，刨花板体积电阻率呈下降趋势，并借此讨论了刨花板的抗静电机理，分析了抗静电性能。研究结果表明：抗静电剂ＳＮ与石墨或甘油共同作为抗静电添加剂时，刨花板体积电阻率下降明显。与普通刨花板相比，电阻率下降了二个数量级。此外，刨花板的含水率和密度，对其抗静电性能也有较大影响。     

Elastic properties of the extruded tubular particleboard

Abstract

Particleboard can be commonly produced by flat-pressing and extrusion methods. The elastic properties of the flat-pressed particleboard have been studied a lot, but the extruded particleboard has not had much attention. Six elastic properties of two commercial extruded tubular particleboards with different solid density were measured by a three-point bending test and electric resistance gages method. The elastic modulus in the extruded direction of the tubular particleboard is only one-tenth of the other two directions. The extruded tubular particleboard can not only be regarded as an orthotropic material but also a transverse surface isotropic material. The isotropic plane is the transverse section of the extruded particleboard which is different from the flat-pressed particle with the length–width plane as the isotropic plane. The checking of the data we measured demonstrated suitability and rationality.     

The lamination influence on properties of agro-based particleboard

Abstract

Response surface methodology (RSM) based on a three-level, three-variable central composite rotatable design was applied to evaluate the effects of the parameters such as ratio of rice straw (Oryza sativa)/poplar (Populus deltoids) wood particle bonded with urea-formaldehyde resin in panels, species of wood veneer coating these panels and amount of adhesive in glue line on the modulus of rupture (MOR), internal bonding (IB), and thickness swelling (TS) of panels. Mathematical model equations were derived by computer simulation programming to optimize the properties of the particleboard. These equations that are second-order response functions representing MOR, IB, and TS were expressed as functions of three operating parameters of panel properties. Predicted values were found to be in a good agreement with experimental values (R ² values of 0.96, 0.98 and 0.98 for MOR, IB, and TS, respectively). This study has shown that the RSM could efficiently be applied for modeling panel properties. It was found that the variables affected the properties of panels. Straw usage up to 30% in the mixture did not cause a significant decrease in MOR, IB, and TS. Using beech veneer and 190 g/m² glue line had the highest MOR and lowest TS.     

Improvement on the properties of gypsum particleboard by adding cement

Gypsum particleboard (GPB) has high thickness swelling (TS), high water absorption (WA), and low mechanical properties compared with cement-bonded particleboard. The properties of GPB were improved by adding cement. The experimental results showed that GPB with the added cement had good physical and mechanical properties compared with those of gypsum particleboard with no added cement. The TS and WA of gypsum particleboard with added cement were reduced by 10%. The mechanical properties of GPB, such as internal bond strength (IB), modulus of rupture (MOR), and modulus of elasticity (MOE), increased when the GPB was made with added cement. The properties of GPB improved relative to the quantity of cement added. With an increase of cement content from 5% to 10%, the TS and WA were reduced, and the IB, MOR, and MOE were increased. In contrast, the TS and WA increased and the IB, MOE, and MOR decreased when the cement content was increased from 15% to 30%. Thus the physical and mechanical properties of GPB were successfully improved when the added cement content was 10%.An outline of this paper was presented at the 47th Annual Meeting of the Japan Wood Research Society in Kochi, April 1997     

无机复合型阻燃剂对稻草刨花板阻燃性能的影响

选用氢氧化铝(ATH)与硼酸锌(ZB)组成的无机复合型阻燃剂压制阻燃稻草刨花板,采用锥形量热仪法研究不同配比的ATH和ZB对稻草刨花板阻燃性能的影响。结果表明:无机复合型阻燃剂能有效减少稻草刨花板的热释放和烟释放,减少烟气中CO和CO2的释放浓度,降低燃烧过程中的质量损失速率,表现出良好的阻燃抑烟效果;ATH与ZB具有协同阻燃作用,ZB的加入能有效提高复合阻燃剂的阻燃效果,减少ATH的用量,10%的ATH用量可达到比较好的阻燃效果。     

环境温度对刨花板生产质量的影响及改进方法

本项研究对气温(尤其在冬季)是如何影响刨花板生产进行了分析。通过对不同季节时的两种极端情况——较高的板坯芯层温度和较低的板坯芯层温度在热压过程中板坯芯层渴度的变化,进一步说明了芯层温度对热压时间以及刨花板质量的影响,并就如何解决这一问题提出了建议。     

Mechanical behavior and springback of acetylated particleboard made in different press times

In this study, the effects of acetylation and press time on the heat transfer from the surface to the core on the particleboard mat, springback, internal bonding, modulus of elasticity, and modulus of rupture were determined. Particles were soaked in the acetic anhydride for 24 h and heated in an oven at 120°C for 40 minutes, 3 h and 6 h to achieve three weight gain levels of 8%, 12%, and 17%, respectively. Acetylated and control boards were produced with 10% melamine urea formaldehyde (regarding the particles dry weight) and pressed for 5, 6, and 7 minutes. During the pressing process, the heat transfer to the core layer of the mat was measured by thermocouple made of Cr-Ni wires. It was found that the increase of acetylation level leads to significant reduction in heat transfer during manufacture process and develops springback which in turn, results in density loss. Findings indicated that these defects were correlated with the press time and compensated by the press time prolongation. Strength loss of the acetylated boards was due to debonding of the constituent that compensated somewhat with increasing press time.     

Performance of particleboard manufactured using air-injection press I: effects of air-injection press on preventing blowout of board manufactured from low-moisture particles

An air-injection press (AIP) was developed to prevent accidental blowouts of boards during production. In this study, the effects of the AIP on preventing blowouts were investigated by artificially creating a blowout-prone condition, and the press was shown to be effective in preventing blowouts. The modulus of rupture of the boards was almost constant irrespective of pressing time. Longer pressing time resulted in higher internal bond strength when pressed at 170 °C. The thickness swelling of the boards pressed at 170 or 190 °C was almost uniform irrespective of pressing time, and the manufactured boards showed performance similar to those manufactured with an ordinary press. The AIP prevented blowouts sufficiently even when the pressure of the injected air was reduced, and this reduction did not adversely decrease the performance of the boards. Air injection reduced formaldehyde emissions from the board.     

Some of the properties of particleboard made from paulownia

The objective of this study was to determine some of the properties of experimental particleboard panels made from low-quality paulownia (Paulownia tomentosa). Chemical properties including holocellulose, cellulose, lignin contents, water solubility, and pH level of the wood were also analyzed. Three-layer experimental panels were manufactured with two density levels using urea–formaldehyde as a binder. Modulus of elasticity (MOE), modulus of rupture (MOR), internal bond strength (IB), screw-holding strength, thickness swelling, and surface roughness of the specimens were evaluated. Panels with densities of 0.65 g/cm³ and manufactured using a 7-min press time resulted in higher mechanical properties than those of made with densities of 0.55 g/cm³ and press times of 5 min. Based on the initial findings of this study, it appears that higher values of solubility and lignin content of the raw material contributed to better physical and mechanical properties of the experimental panels. All types of strength characteristics of the samples manufactured from underutilized low-quality paulownia wood met the minimum strength requirements of the European Standards for general uses.     

Formation of the density profile and its effects on the properties of particleboard

Summary Two types of particleboards bonded with an isocyanate resin, one with uniform vertical density profile (homo-profile), and the other with conventional U-shaped profile, were fabricated to various density levels using lauan (Shorea spp.) particles. The fundamental relationships between the density profile and the board properties were determined, and the results are summarized as follows: 1. In homo-profile boards, the moduli of rupture (MOR) and elasticity (MOE), internal bond (IB) strength, and screw withdrawal resistance (SWR), are highly correlated to the board mean density. 2. The bottom limit of the board density is estimated to be ca. 0.25 g/cm³, based on the correlation regressions between mechanical properties and mean density. 3. At equal mean density level, the MOR and MOE of the conventional particleboards are higher than the homo-profile boards, due to the higher density near the faces. However, the reverse is true for IB, owing to the presence of the low density core in the former. 4. The net impact of peak density on MOR and MOE is greater at higher mean density level while raising the core density results in more pronounced improvement in IB at lower density. 5. In addition to the compaction ratio, the dimensional stability of the board is also affected by the peak area and mat moisture content. Received 9 January 1997