Durability evaluation of particleboards by accelerated aging tests

Summary Specimens of four commercially produced particleboards were exposed to various accelerated aging treatments: 1) 6-cycle ASTM D-1037 exposure, 2) 6-cycle WCAMA exposure, 3) BS 5669 test, 4) cyclic soak-dry test, and 5) cyclic boil-dry test. Thickness swelling (TS) and internal bond strength (IB) were measured after each step of each cycle. Phenol and phenol (face)/isocyanate (core)bonded boards are more durable than urea and melamine urea bonded boards. The effect of treatment 1) is most severe on TS and IB retention, followed in order by treatments 2), 5), 4) and 3). When the value of springback reached about 35%, IB became equal to zero.     

柠檬桉水泥刨花板若干工艺因子的研究

通过对柠檬桉制造水泥刨花板的可能性、水泥/刨花的比率、水泥种类与板材性能关系等因素的研究,结果表明:使用添加剂或对木材进行热水处理可以使柠檬桉成为适宜制造水泥刨花板的树种。     

Modelling of vertical density profile of particleboard,manufactured from hardwood sawmill residue

Abstract

Particleboards are generally made in three layers using softwood as the major raw material. Limitation on natural wood resources and concerns about the carbon footprint of products has created a significant interest in environmentally friendly or ‘green’ building materials. Hardwood sawmill residue, which has been disposed as solid waste, was investigated by authors as the main raw material for producing particleboard at RMIT University, Australia. Physical and mechanical properties of final particleboard were measured and analysed against original materials and process variables. The density of a particleboard along its thickness direction is not uniform, and is called the vertical density profile (VDP) which is dependent upon processing parameters. The VDP influences particleboard properties including flexural strength and its dimensional stability and fastening capacity. It is important to influence the formation of the VDP, altering processing variables, to achieve optimum particleboard properties. This paper presents an attempt to develop a model to predict the formation of the VDP of hardwood residue particleboard compared to processing parameters, using the theory of experimental design. The advantages of such a model in optimising particleboard properties are also discussed.     

Effect of flake geometry on properties of cement-bonded particleboard from mixed tropical hardwoods

Summary Laboratory scale cement-bonded particleboards were made from mixed particles of three tropical hardwoods. Boards were three-layered comprising of 2 mm thick sawdust face and 4 mm thick core layers made from flakes of three lengths-12.5 mm, 25.0 mm and 37.5 mm and two thicknesses of 0.25 mm and 0.50 mm. The panels were fabricated at three density levels of 1,050 kg/m³, 1,125 kg/m³ and 1,200 kg/m³. From the statistical factorial analysis carried out, flake length, flake thickness and board density had significant effects at 1% level of propability on the properties of the tested panels. Mean MOR ranged from 5.22 to 11.15 N/mm²; MOE-2,420 to 4,820 N/mm²; water absorption and thickness swelling following 144 hours soak in water, 32.95 to 46.00% and 0.35 to 5.47% respectively. The longer and thinner the flakes, the stronger, stiffer and more dimensionally stable the experimental cement-bonded particleboards. Similarly, the higher density panels generally exhibited higher strength values in terms of MOR and MOE and were more dimensionally stable. MOR, MOE, water absorption and thickness swelling were found to be highly correlated with flake length, flake thickness and panel density. Correlation coefficients (R) for these relationships were 0.888 to 0.986 for the combined variables; and 0.574 to 0.992 for the individual factors. In all the cases tested, the regression relationships were linear.     

Pyrolytic characteristics of burning residue of fire-retardant wood

In order to investigate the pyrolytic characteristics of the burning residue of fire-retardant wood, a multifunctional fire-resistance test oven aimed at simulating the course of a fire was used to burn fire-retardant wood and untreated wood. Samples at different distances from the combustion surface were obtained and a thermogravimetric analysis (TG) was applied to test the prrolytic process of the burning residue in an atmosphere of nitrogen. The results showed that: 1) there was little difference between fire-retardant wood and its residue in the initial temperature of thermal degradation. The initial temperature of thermal degradation of the combustion layer in untreated wood was higher than that in the no burning wood sample; 2) the temperature of the flame retardant in fire-retardant wood was 200°C in the differential thermogravimetry (DTG). The peak belonging to the flame retardant tended to dissipate during the time of burning; 3) for the burning residue of fire-retardant wood, the peak belonging to hemicellulose near 230°C in the DTG disappeared and there was a gentle shoulder from 210 to 240°C; 4) the temperature of the main peaks of the fire-retardant wood and its burning residue in DTG was 100°C lower than that of the untreated wood and its burning residue. The rate of weight loss also decreased sharply; 5) the residual weight of fire-retardant wood at 600°C clearly increased compared with that of untreated wood. Residual weight of the burning residue increased markedly as the heating temperature increased when burning; 6) there was a considerable difference with respect to the thermal degradation temperature of the no burning sample and the burning residue between fire-retardant wood and untreated wood. __________ Translated from Journal of Beijing Forestry University, 2006, 28(3): 133–138 [译自: 北京林业大学学报]     

Fermentation characteristics of vinegar residue and some natural materials

1 Introduction Being the world’s largest agricultural country, China has over one billion tons of cellulosic wastes from farms and forests every year. With petroleum prices and the number of automobiles ever increasing in China, there will be more and more needs for alterna tive fuel sources. Using corn to make ethanol is only a part of the potential from agriculture. If cellu lose-containing material like straw and cornstalks could be converted into liquid fuels, it could assist the nation…     

几种防霉剂对提高非木材刨花板抗霉性能的研究

以17种防霉剂对竹材等4种非木材刨花板做了抗霉性能试验。结果8、9、7、6号防霉剂配方效果最好，分别施加这四种药剂的竹材等4种刨花板抗霉性能与落叶松刨花板相同，优于柳刨花板。将9号防霉剂施加于甘蔗渣、豆秸和玉秆刨花析对达到了较好的效果。     

竹材液化树脂发泡材料的降解性能和热老化性能评价

将竹材液化树脂发泡材料分别置于土壤微生物侵蚀、干(湿)热老化、氙光辐照条件下一定时间,采用热重、红外及电镜扫描法,对比分析处理前后材料的性能变化.结果表明,该材料易于被微生物降解;经干热、湿热老化处理后,材料的质量降低,压缩强度反而提升;经氙光辐照处理后,其质量和压缩强度下降.在实际应用中,该材料经覆面处理后,可作为芯材,用作建筑外墙保温材料.     

提高再生刨花板性能的若干途径探讨

对提高再生刨花板物理力学性能的若干途径进行的研究结果表明：提高再生刨花板密度有助于其物理力学性能的改善;增加施胶量对再生刨花按常规工艺所制刨花板的静曲强度和内结合强度均有改善,但静曲强度仍未达到国标要求;如果将超过５０％的原生刨花加入到再生刨花中去,所制刨花板可以达到国标ＧＢ／Ｔ４８９７－９２一级品的要求。     

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.     

狼尾草刨花板制造工艺研究

采用正交实验设计的方法,研究了施胶量、热压温度、热压时间等工艺因素对狼尾草刨花板的静曲强度、弹性模量、内结合强度、吸水厚度膨胀率等性能的影响.研究结果表明:狼尾草应用在刨花板制造中是可行的;其中狼尾草刨花板制造的最佳工艺参数为施胶量13%、热压时间40 s/mm(板厚)、热压温度180℃.     

Performance of particleboard manufactured using air-injection press II: effects of board density and thickness on the performance of board manufactured from low-moisture particles

Particleboards of different densities (0.6, 0.7 and 0.8 g/cm³) and thicknesses (10 and 20 mm) were manufactured from low-moisture particles using an air-injection press. The effects of the air injection on preventing blowout of the boards of different densities and thicknesses were investigated by artificially creating blowout-prone conditions using metal frames. The effects of the air-injection pressure on the board performance were also investigated. 10-mm-thick boards of 0.8 g/cm³ pressed at 170 °C blew out when air was not injected, but were successfully manufactured by injecting air. 10-mm-thick boards at 150 °C showed constant internal bond (IB), regardless of density, but at 170 °C, IB was higher in boards of higher densities. This was likely due to accelerated hardening of the urea–formaldehyde resin at 170 than 150 °C. At both pressing temperatures, low air-injection pressure did not cause blowout and a reduction in board performance. Air injection also prevented the blowout of thick boards of 20 mm and enabled successful manufacture, showing its effectiveness. The IB of the 20-mm-thick board manufactured using the air-injection press exceeded that of 20-mm-thick board manufactured using an ordinary hot press.     

STUDY ON COMPONENTS OF FURFURAL RESIDUE FROM CORNCOB

In this paper,the components of furfural residue are analyzed.Total sugar contentoccupies47.36％ of absolute drying residue,and glucose occupies 83.23％ of total sugar content.Bycombining the phenyl nucleus exchange reaction with nitrobenzene oxidation,the quantity of struc-tural units of phenyl nuclei was determined,products from syringyl units occupy 50％ of klasonlignin Especially,diphenyl methane type syringyl units occupy 38.80％,and guaiacyl units 25％,other condensed guaiacyl units about 20％.The furfural residue is not a good material for the manu-facture of adhesives,but for active carbon.The yield of furfural residue may achieve about 350thousand tons per year,but it has not been used in industry in China.     

Application of response surface methodology for evaluating particleboard properties made from cotton stalk particles

High-quality wood resource scarcity as well as population growth and demand of wood have encouraged the use of alternative sources of lignocellulosic materials. In this study, the possibility of producing particleboard from waste cotton stalks is evaluated. The effects of the independent variables included weight ratio of melamine-formaldehyde to urea-formaldehyde, shelling ratio and the percentage of cotton stalks to poplar in the core layer were analyzed in the form of response surface methodology based on second-order multiple linear regression model. The results showed that there was perfect agreement between the estimated values and observed data, as with an increase in the ratio of melamine-formaldehyde resin to urea-formaldehyde, shelling ration and amount of poplar in the core layer of panels, modulus of rupture, modulus of elasticity and internal bonding increase. The optimal point of use of investigated variables included 18.30% melamine-formaldehyde, 30.35% thickness of the surface layers and 10.70% of poplar in the core layer.     

沙棘籽渣中低聚原花青素提取和精制工艺研究

研究了沙棘籽渣中低聚原花青素提取和精制工艺。采用正交试验法确定了沙棘籽渣中低聚原花青素提取的最佳条件：70％的乙醇溶液为提取剂，提取温度45℃，提取次数2次(60min／次)，料液比1：8(w／v)；采用大孔吸附树脂精制低聚原花青素，实验结果表明*型树脂对沙棘籽渣中低聚原花青素有良好的精制效果。     

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.     

Durability of thermally modified timber from industrial-scale processes in different use classes: Results from laboratory and field tests

Material from four common European processes of industrial heat treatment of timber was examined comparatively with reference to biological laboratory standard tests and field tests in soil contact and above ground. The thermally modified timber (TMT) used in the study was: Plato wood from the Netherlands, ThermoWood from Finland, New Option Wood (NOW) from France, and oil-heat-treated wood (OHT) produced in Germany. Tests of resistance to basidiomycetes (EN 113, 1996) and tests of resistance to soft rotting microfungi and other soil-inhabiting microorganisms (EN 807, 1997) showed substantially lower mass losses of TMT compared with controls. Only slight differences in mass loss were found between the four thermally modified materials. Based on results from laboratory standard tests all tested heat-treated materials were classified as durable to moderately durable [durability class (DC) 2-4], analogous to the classification of natural durability (EN 350-1, 1994). In contrast, the classification of TMT samples after 5.5 years' exposure in soil contact, in accordance with EN 252 (1990), was slightly durable to not durable (DC 4-5), whereas the classification obtained after 5.5 years' exposure in double layers in European hazard class (EHC) 3 (EN 335-1, 1992) was very durable to moderately durable (DC 1-3). On the basis of 5.5 years' field testing, thermally modified material (independent of the treatment process and supplier) appears not to be suitable for in-ground contact application. However, the suitability of TMT for use out of ground in EHC 3 was ascertained and is recommended.     

Effects of density and resin content on the physical and mechanical properties of scrimber manufactured from mulberry branches

The silk industry in China produces a large amount of mulberry branches as by-product every year. Mulberry branches have high longitudinal toughness and good overall mechanical properties. However, these branches are incinerated because their utility in other industries is limited by their small size. This study determines the feasibility of manufacturing scrimber from mulberry branches by using cold pressing method, followed by thermo-curing with different densities and resin contents. Results show that density [ranging from (0.81–1.24) g/cm³] exerts a greater effect on the shear strength, modulus of rupture (MOR), and modulus of elasticity (MOE) than resin content (changing from 8 to 20 %). The increase rate slows down when the density exceeds 1.1 g/cm³ and the resin content reaches more than 12 %. The strength-to-weight ratio analysis shows that the MOR/density and MOE/density maximum at 1.02–1.10 g/cm³. The density and resin contents of mulberry scrimber with cold compress and heat setting can be set to 1.0–1.1 g/cm³ and at approximately 12 %, respectively. The mechanical properties of the product meet the maximum requirement indicated in the Chinese national standard for construction. Mulberry scrimber can be a very promising supplement for wood because of its good performance, abundant supply, and renewability.     

正交设计法优化沙棘果渣中总黄酮的提取工艺

研究了从沙棘果渣中提取总黄酮的工艺,考察了提取溶剂、乙醇浓度、提取温度、提取时间及剂量对提取效果的影响,最后通过正交实验确定了最佳工艺条件;80℃下采用60%的乙醇浸提,固液比1:7,回流提取3次,每次1h.