Evaluation of wood-based panel durability using bending properties after accelerated aging treatments

The durability of wood-based panels was evaluated by comparing the bending properties of panels subjected to five accelerated aging treatments with the bending properties of panels that had experienced 5 years of outdoor exposure in Shizuoka City, Japan. In each accelerated aging treatment, methylene diphenyl diisocyanate-bonded panels showed higher bending retention than phenol formaldehyde (PF)-bonded panels. The bending retentions after six repeated cycles of the JIS-B, APA D-1, and ASTM treatments showed a correspondence of nearly one-to-one in the data for the three different treatments. The Shizuoka City 5-year outdoor exposure test data showed that the bending retentions of all panels decreased with time. In particular, the bending retentions of PF resin-bonded particleboard and oriented strandboard made from aspen were less than 30% and 10% of the original values, respectively, after the 5-year exposure period. The deterioration of the bending properties after the 5-year outdoor exposure in Shizuoka City was the same as that for six repetitions of the ASTM treatment.     

The aging effects of water immersion treatments in wet-bending for standardized testing of wood panels

The durability of wood-based panels is one of the most important properties when they are used in residential construction. The main objectives of this study were to investigate the quantitative relationship between the Wet-bending A test and the Wet-bending B test, examine the aging effects of the treatments specified in the wet-bending methods, and discuss the relationship between wet-bending and outdoor aging tests conducted in Shizuoka, Japan. Wet-bending tests, internal bond tests after humidity treatment, and outdoor aging tests in Shizuoka were conducted using eight types of commercial wood-based panels. A linear relationship was found between the load-carrying capacity (LCC) from the Wet-bending A test and the LCC from the Wet-bending B test. The LCC from Wet-bending B could be obtained from LCC from Wet-bending A by multiplying it by 0.9, which may be applicable as a quantitative ratio of aging effects between the two. LCC for methylenediphenyl diisocyanate-bonded panels recovered to almost 100% of the initial strength. A certain relationship was found between the LCC after Wet-bending A and the LCC after a 1-year outdoor exposure in Shizuoka. Internal bond strength showed a good correlation between the JIS-A treatment and the 1-year outdoor exposure treatment.     

Evaluation of the weathering intensity of wood-based panels under outdoor exposure

In this study, the deterioration of wood-based panels at eight sites in Japan was investigated using outdoor exposure tests. In particular, the modulus of rupture (MOR) retention and internal bond strength (IB) retention after 5-year exposures were compared among panels and sites. The deterioration of panels located in southern Japan was higher than that of panels in northern Japan. To quantify the regional differences, the deterioration rates were calculated; the values showed clear regional differences. The deterioration rate for areas that receive much rain in the summer was higher than the rates for other sites. To eliminate regional differences, we carried out an analysis in terms of the “weathering intensity,” a factor which combines weather conditions (precipitation and temperature). Panels for which deterioration progressed extensively during exposure periods showed a strong correlation between strength retention and the weathering intensity. The significance of these parameters is discussed.     

Modified method for evaluating weathering intensity using outdoor exposure tests on wood-based panels

The deterioration of wood-based panels at eight sites in Japan over 7?years of outdoor exposure was investigated. In particular, the modulus of rupture (MOR) retention and internal bond strength (IB) retention after 7?years of exposure were compared among panels and sites. The deterioration of panels was greater in southern Japan than in northern Japan. The strength retentions in northern Japan decrease linearly, while those in southern Japan decreased exponentially. To quantify regional differences, deterioration rates were calculated based on three different weather conditions (precipitation, temperature, and sunlight hours), and the significance of each of these parameters on panel deterioration was determined. We found that the correlation coefficients between both IB and MOR retention and weathering intensity were the same whether we used 10-day, monthly, or daily weathering data.     

室外用人造板耐老化性的评估研究进展

介绍国内外室外用人造板耐老化性的2种测定方法:室外自然老化法和室内加速老化法,分析其相关性,并重点分析室内加速老化法的主要评定指标,为今后我国室外用人造板耐老化性的评定方法研究,及相关标准体系的建设,提出建议.     

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.     

Bond durability of kenaf core binderless boards II: outdoor exposure test

An outdoor exposure test was conducted on kenaf core binderless boards (pressing temperatures 200°, 180°, and 160°C; pressing pressure 3.0 MPa, time 10 min, target board thickness 5 mm, target board density 0.8 g/cm³) to estimate their bond durability. Modulus of rupture (MOR), modulus of elasticity (MOE), internal bonding strength (IB), thickness change, weight loss, Fourier transform infrared (FTIR) spectra, and color difference (ΔE*) by the CIE L^*a^*b^* system were measured at various outdoor exposure periods up to 19 months. These values were then compared with those of a commercial medium-density fiberboard (MDF; melamine-urea-formaldehyde resin; thickness 9.0 mm, density 0.75 g/cm³). Generally, dimensional stability and the retention ratios of MOR, MOE, and IB after the outdoor exposure test increased with increased pressing temperature of binderless boards. The MOR retention ratio of the kenaf core binderless boards with a pressing temperature of 200°C was 59.5% after 12 months of outdoor exposure, which was slightly lower than that of the MDF (75.6% after 11 months of outdoor exposure). Despite this, the bond durability of the kenaf core binderless boards should be viewed as favorable, especially when considering the fact that the retention ratio of 59.5% was achieved without binder and without obvious element loss. Part of this report was presented at the International Symposium on Wood Science and Technology, IAWPS2005, November 27-30, 2005, Yokohama, Japan     

Bond durability of kenaf core binderless boards I: two-cycle accelerated aging boil test

A two-cycle accelerated aging boil test was conducted on kenaf core binderless boards to estimate their bond durability. This is one of the methods to estimate the bond quality of kenaf core binderless boards, as stipulated by Notification 1539 of the Ministry of Land, Infrastructure, and Transport, October 15, 2001, for the Building Standard Law of Japan. Generally, retention ratios of modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond (IB) strength after the boil test increased with increased pressing temperature. In particular, the MOR retention ratio of boards with a pressing temperature of 200°C (average 106.4%) was higher than that of a commercial medium-density fiberboard (MDF) (melamine-urea-formaldehyde resin) (average 72.7%), and the value sometimes exceeded 100%. The durability of kenaf core binderless boards with a pressing temperature of 200°C compared favorably with that of the commercial MDF (melamine-urea-formaldehyde resin), having almost the same retained strength values after the boil test. Part of this article was presented at the International Symposium on Wood Science and Technology, IAWPS2005, November 27–30, 2005, Yokohama, Japan     

Effects of climate change on reduction of internal bond strength of particleboard subjected to various climatic conditions in Japan

The effects of climate change on the reduction of internal bond strength (IB) of particleboard subjected to various climatic conditions in Japan were predicted. The temperature increased throughout Japan with increasing greenhouse gas (GHG) emissions, so the climate deterioration index (climate index for predicting the IB reduction of particleboard; a high index indicates a large IB reduction) also increased to decrease IB. The number of low-temperature areas decreased because of climate change. The rupture of bonding points in particleboard caused by outdoor exposure led to a IB reduction, and biodeterioration accelerated this reduction. In high-temperature areas, particleboard was found to be prone to biodeterioration, and the IB significantly reduced. An area wherein there was a significant decrease in the IB spread along the Pacific Ocean side of western Japan and the Sea of Japan in central Japan in relation to increasing GHG emissions. Particleboards are difficult to use outdoors because of climate change.     

酚醛刨花板加速老化试验的研究

刨花板的耐老化性质是它作为建筑用材的一项重要指标。本试验采用人工老化方法，讨论加速老化因素对马尾松酚醛刨花板耐老化能力的影响，并对几种加速老化方法进行分析比较。结果表明：循环数、冷冻、喷蒸、干燥等因素对老化结果有不同程度的影响；不同的加速老化试验方法对刨花板ＭＯＲ、ＩＢ和ＴＳ的影响程度也不相同；可采用热水浸泡－干燥循环法代替ＡＳＴＭＤ１０３７的６循环加速老化试验；可把沸水煮１小时方法作为工厂对产品的耐侯性质量控制法。     

Effect of thermo-mechanical refining on properties of MDF made from black spruce bark

The effects of thermo-mechanical refining conditions on the properties of medium density fiberboard (MDF) made from black spruce (Picea mariana) bark were evaluated. The bark chips were refined in the MDF pilot plant of Forintek Canada Corporation under nine different refining conditions in which preheating retention time was adjusted from 3 to 5 to 7 min and steam pressure was set at either 0.6, 0.9 or 1.2 MPa. The resulting bark fibers were blended with 12% UF resin (based on oven-dry fiber weight) using a mechanical blender. The resinated fibers were manually formed into fiber mats and hot-pressed into MDF panels using consistent parameters. Two panels for each refining condition were produced, resulting in a total of 18 panels. Analysis of variance (ANOVA) was used to analyze the significance of factors. Regression coefficients and 3D contour plots were used to quantify the relationship between panel properties and the two test factors. The results from this study indicated that the preheating retention time was a significant factor for both modulus of rupture (MOR) and modulus of elasticity (MOE), the steam pressure was a significant factor for internal bond strength (IB), MOR and MOE, whereas both factors were insignificant for thickness swelling, water absorption and linear expansion. The properties of MDF panels were quadratic functions of retention time and steam pressure. Compared to the ANSI standard for 120-grade MDF, most panels with a nominal density of 950 kg/m³ had very high IB (>1 MPa) and acceptable MOR, MOE and dimension stabilities. These results suggest that black spruce bark residues can be considered as a potentially suitable raw material for manufacturing MDF products.     

室外竹质人造板耐潮湿性能研究

室外自然老化法和5种加速耐潮湿试验方法对2种竹质人造板的物理力学性能均有明显降低,试验结果表明:高温干燥和沸煮对板材性能的影响最显著,对于同一种方法处理后的试件,横向上性能降低幅度比纵向上大,静曲强度较弹性模量降低更为显著。15个月的室外自然老化法试验结果接近于6 h水煮-冰冻-干燥法的试验结果,板材性能随时间延长逐渐降低,但降低幅度逐渐变小,还需放置更长时间进行分析比较,以真正反映竹质人造板的耐潮湿性能。     

竹纤维/聚丙烯复合材料的耐老化性能

采用挤出成型制备了竹粉增强聚丙烯复合材料,研究竹粉/聚丙烯复合材料在紫外加速老化与湿热老化后的力学性能变化与尺寸稳定性.结果表明:在紫外线加速老化200 h后,复合材料的弯曲强度与弯曲模量无显著变化,试件宽度与厚度在紫外加速老化前后也无显著改变;但湿热老化对复合材料的弯曲强度与弯曲模量有显著影响,在沸水中浸泡2h后,复...     

Deterioration of wood-based boards subjected to outdoor exposure in Tsukuba

Various types of wood-based boards were analyzed for deterioration after being exposed to an outdoor environment for 5 years in Tsukuba, Japan. In phenol–formaldehyde resin bonded particleboard (PB(PF)) and aspen oriented strand board (OSB(aspen)), longer exposure caused a greater reduction in the modulus of rupture and internal bond strength, an increase in the coefficients of variation, and a decrease in 95 % lower tolerance limit at the 75 % confidence level (95TL). Nail-head pull-through and lateral nail resistance were also reduced by outdoor exposure, but their coefficients of variation and 95TL were not significantly affected. In contrast, methylene diphenyl diisocyanate bonded medium density fiberboard (MDF(MDI)) only showed a slight deterioration of these properties even after 5-year exposure, and the coefficients of variation and 95TL hardly changed. After 5-year exposure, the retention of shear load in one-plane at relative displacement of 1.0 mm was high in MDF(MDI) and OSB(aspen) at 93.5 and 78.5 %, respectively, but low in PB(PF) at 41.1 %. As with PB(PF), OSB(aspen) also showed a sharp decrease in the modulus of rupture and internal bond strength, but only slightly reduced shear load in one-plane.     

我国室外人造板标准体系的构建

总结我国主要室外人造板产品的种类、产量及分布情况,汇总我国室外人造板相关标准,并与室外人造板标准进行对比分析,指出我国现有标准设置的问题,提出我国应构建包括产品标准和性能检测方法的室外人造板独立标准体系,以促进我国室外人造板的健康快速发展。     

Effect of element type on the internal bond quality of wood-based panels determined by three methods

Three mechanical tests with different loading modes were conducted to evaluate the effect of element type on the internal bond quality of wood-based panels. In addition to the internal bond test, which is commonly used for mat-formed panels, interlaminar and edgewise shear tests were used to test oriented strandboard (OSB), particleboard, medium-density fiberboard (MDF) of two thicknesses, and plywood. The following results were obtained. Epoxy resin proved to be suitable for determining the interlaminar shear modulus instead of hot-melt glue. There was a linear relation between panel density and interlaminar shear modulus and a linear correlation between the interlaminar shear strength and internal bond (IB) strength for the mat-formed panels tested. OSB had the highest edgewise shear modulus, and MDFs had the highest edgewise shear strength in this study. The modulus/strength ratio also depended on both panel type and loading mode. The relation between the shear moduli determined from the edgewise and interlaminar tests indicated the characteristics of the shear properties of panels made of different elements.Part of this paper was presented at the Fourth International Wood Science Symposium, Serpong, Indonesia, September 2002     

Effects of water soaking and outdoor exposure on modulus of rupture and internal bond strength 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 board properties were analyzed. The relationships between the deterioration of board properties resulting from water soaking and those arising from outdoor exposure were also analyzed. At 100 °C, the modulus of rupture (MOR) and internal bond strength (IB) of the PF board decreased significantly within the first hour, and subsequently constant values were shown with increasing soaking time. This low constant value was defined as the lower limit. At 70 °C, both the MOR and IB decreased with increasing soaking time, and reached the lower limit. At 40 °C, however, neither decreased significantly with increasing soaking time and neither reached the lower limit. The MOR of the MDI board showed the same trend as the PF board. However, the IB of the MDI board showed a different trend to the PF board, that is, the lower limit of IB required extensive soaking, even at 100 °C. The MOR and IB of both the PF and MDI boards reached the lower limit when thickness change peaked. On the other hand, the MOR and IB for outdoor exposure were lower than those for water soaking, even at the same thickness change. The MOR and IB of water soaking decreased owing to the collapse of the bonding points caused by board swelling. On the other hand, the board properties of outdoor exposure decreased owing to the collapse of the bonding points, and biodegradation also added to the decrease.     

单板层积材的加速老化性能研究

本文对高频胶合的马尾松LVL和杨木LVL的老化性能进行了讨论,并比较了乳液酚醛树脂胶和酸固化酚醛树脂胶在BDB28和A1080加速老化后的胶合剪切强度的损失率。得出的结论如下:1)乳液酚醛树脂肢胶合的马尾松LVL,胶合剪切强度随老化时间的延长逐渐趋于稳定,最后稳定在老化前强度的70％左右;2)乳液酚醛树脂胶的老化性能比酸固化酚醛树脂胶好;3)对于乳液酚醛树脂胶马尾松LVL和酸固化酚醛树脂胶杨木LVL,可以用BDB28处理方法代替A1080加速老化方法快速测定其胶合剪切强度的损失率。     

Physical and mechanical properties of particleboard from roselle (Hibiscus sabdariffa) stalks and eucalyptus (Eucalyptus camaldulensis) wood particles

Abstract

The objective of this work was to evaluate the performance of particleboard manufactured from roselle (Hibiscus sabdariffa) stalks and eucalyptus (Eucalyptus camaldulensis) wood. The manufacturing parameters were various roselle (Hibiscus sabdariffa) ratios in the mixture (0, 25, 50, 75 and 100%) and press time (3, 5 and 7 min). Modulus of elasticity (MOE), modulus of rupture (MOR), internal bonding (IB) strength values and thickness swelling (TS) after 24-hour water soaking of the panels were determined according to the procedure of European Union (EN) Standard. The results of the study demonstrate that roselle stalks can be an alternative raw material source for particleboard industry. With an increase of roselle particles from 0% to 100%, the TS was reduced, and the IB, MOR and MOE were increased. The highest MOE, MOR, IB strength and TS values of the samples were found as 2754.18, 16.81, 0.89 N/mm² and 15.26% for the panels made using 100% roselle with a 7-min press time, respectively.     

Fracture energy vs. internal bond strength – mechanical characterization of wood-based panels

Abstract

A new testing method measuring the specific fracture energy of wood-based panels in Mode I is proposed. Three types of wood-based panels, i.e. oriented strand board (OSB), particleboard (PB) and medium density fibreboard (MDF) are investigated, using fracture energy and the industrial European standard method of internal bond strength according to EN 319. Double cantilever beam specimens are notched in the middle layer to introduce an initial crack. To apply tensile load perpendicular to the surface of the panels to open the crack in Mode I specimens were adhesively bonded to steel braces. Besides the calculation of the total fracture energy an advanced analysis of the load–displacement curve was also performed. Results of the fracture energy method were compared to internal bond strength (IB). Specimen shape is optimized for industrial purposes using double cantilever beams, while the determination of the fracture energy is performed by simple integration of the load–displacement curve. While IB showed a large scattering of data, the fracture energy test yielded statistically significant differences between the board types.