密度控制仪在中密度纤维板生产中的影响因素

通过对中密度纤维板生产线所用的MD-3密度控制仪应用和测试，分析了可能影响控制精度的一些因素，找出了一定的变化规律，并提出了使用中的注意事项。     

Organo-silane compounds in medium density fiberboard:physical and mechanical properties

We studied the effects of nanoparticles of organo-silane(NOS) compounds in the size range of20–80 nm on physical and mechanical properties in medium density fiberboard,and used NOS at four consumption levels of 0,50,100,and 150 g kg-1dry wood fibers.Density of all treatments was kept constant at 0.67 g cm-3.The water-repellent property of organo-silane significantly reduced water absorption(WA) and thickness swelling but mechanical properties declined due to the reduced proportion of wood-fiber as organo-silane was added to the matrix:the compression ratio of MDF panels and the integrity among wood-fibers both declined,resulting in reduced mechanical properties.We recommend use of 50 g of NOS/kg wood-fiber to improve WA and thickness swelling while retaining acceptable mechanical properties.     

落叶松单宁胶在中密度纤维板生产中的应用

以粉状落叶松单宁胶与传统的酚醛树脂胶制成的中密度纤维板 (MDF)作对比实验 ,证明了落叶松单宁胶制成的板的主要物理力学性能接近于或优于酚醛树脂胶制成的板 ,落叶松单宁胶可基本替代酚醛树脂胶     

Applications of wavelet transformation in the nondestructive test of medium density fiberboard

Taking medium density fiberboards (MDF) as samples, the feasibility of the applications of wavelet analysis in a nondestructive test is discussed in this paper. The main results are as follows: the modulus of elasticity of longitudinal resonance, measured by wavelet analysis, can replace the conventional static modulus of elasticity. Their correlation coefficient is significant (p < 0.01). The defect of samples can be judged by wavelet analysis, which is superior because it is a nondestructive test. __________ Translated from Scientia Silvae Sinicae, 2006, 42(10): 91–94 [译自: 林业科学]     

中密度纤维板MOR和MOE测试影响因素分析

研究了跨距、加载辊直径、支撑辊直径、试件长度、加载速度等因素对中密度纤维板静曲强度和弹性模量试验结果的影响。结果表明:跨距大小及加载速度的改变对测试结果的影响较为明显,跨距增大静曲强度和弹性模量测试结果减小,加载速度增加静曲强度和弹性模量测试结果增大;试件长度、加载辊直径、支撑辊直径的改变对测试结果无明显影响。     

Combined shear and compression analysis using the Iosipescu device: analytical and experimental studies of medium density fiberboard

The possibility of using the Iosipescu shear test device to study the combined shear and compression behavior of anisotropic materials was examined. Measurements were made using both an original (Wyoming version) and an in-house modified Iosipescu shear and compression fixture. Numerical simulation of the combined shear and compression test was carried out to verify the reliability of the modified device. The numerical results were compared with data from experiments on a medium-density fiberboard. The numerical results show good agreement with the experimental results for the shear test in all the three material directions tested. The shapes as well as the values of the strain fields were similar in the numerical and experimental results. Different rotations of the combined shear and compression device were studied using the finite element method to find the combinations that gave reliable results in shear and compression. It was found that the 45° rotation gave the most uniform strain fields in the section between the notches. This rotation was tested on the fiberboard.     

红石中密度纤维板厂清洁生产评析及改进对策

依据国家环境保护部发布的中密度纤维板清洁生产标准,对红石中密度纤维板厂清洁生产现状进行了评析,针对存在的薄弱环节,提出了进一步推行清洁生产的对策:提高思想认识,树立清洁生产观念;健全组织机构,明确清洁生产目标;针对薄弱环节,制订清洁生产方案;加快技术进步,提高清洁生产水平;建立激励机制,促进清洁生产落实。     

Comparison of internal bond strength and compression shear strength of wood-based materials

The purpose of this study was to design a compression shear device for easy and fast measurement of the bonded shear strength of wood-based materials to replace the conventional method used to evaluate internal bond strength (IB). To assess the performance of this device, five differently sized specimens, included group I (dimension 5 × 1 cm), group II (5 × 2 cm), group III (5 × 3 cm), group IV (5 × 4 cm), and group V (5 × 5 cm) cut from commercial particleboard and medium-density fiberboard (MDF) (1.8 cm thick) were tested in compression shear. Only group V (5 × 5 cm) was prepared for the IB test. Results indicated that the compression shear strengths (CS) of particleboard and MDF, loaded in the horizontal or the diagonal direction, were greater than the IB, although a significant correlation existed between the two. This finding suggests that the IB of particleboard and MDF could be accurately estimated from the data collected by the CS test.Part of this report was presented at the Third Pacific Rim Bio-based Composites Symposium, Kyoto, December 2–5, 1996     

工艺参数对稻壳-木刨花复合板内结合强度的影响

采用均匀实验设计方法,通过单因素及两因素间交互作用情况,探讨工艺参数对稻壳-木刨花复合板内结合强度(IB)的影响。在试验研究范围内,密度、芯层比例、芯层施胶量、热压温度、热压时间对复合板IB影响显著,表现为IB随密度的增大先增大后减小,随芯层比例和芯层施胶量的增加而增加,随热压温度和热压时间的增加而减小。当密度为0.77 g/cm3、芯层比例为60%~65%、芯层施胶量为4.5%、热压温度为170℃、热压压力为2.5 MPa、热压时间为20 s/mm时,在兼顾生产效率与生产成本的同时,能够获得IB良好的稻壳-木刨花复合板。     

湖南中密度板生产应对原料和市场挑战的对策

中密度纤维板是市场非常看好的建材,又是一个富有挑战的新兴产业。本文从我省中密度纤维板的生产现状出发,指出了我省中密度纤维板面临的严峻挑战,并提出了应对策略。     

Effects of surface laminate type and recycled fiber content on properties of three-layer medium density fiberboard

ABSTRACT

High global production of medium-density fiberboard (MDF) in recent years could generate an equal quantity of waste MDF at the end of its service life, requiring recycling of waste MDF instead of landfilling or incineration. This study investigated effects of the addition of recycled fiber (RF) obtained from surface laminated MDFs with three different materials to the properties of three-layer recycled MDF (rMDF). Three types of surface laminates such as low-pressure laminate, polyethylene terephthalate, and polyester coating were hammer milled, and then went through a patent-pending fiber recovery system to obtain the resultant RFs that were added to the core layer of rMDF. These RFs at three contents (10, 20, and 30%) were blended with 12% of urea-formaldehyde (UF) resin prior to hot-pressing. Statistical analysis showed that the best internal bonding strength, modulus of rupture, and modulus of elasticity of rMDF panels were obtained for LPL-rMDF with a 20% RF content. Thickness swelling, water absorption, and formaldehyde emission of rMDF were reduced by increasing the RF content. These findings suggest that a minimum RF content of 20% can be replaced with virgin fibers for the rMDF manufacture, indicating the feasibility of recycling waste laminated MDF into three-layer rMDF.     

Evaluating the durability of wood-based panels using internal bond strength results from accelerated aging treatments

In this study, the durability of wood-based panels was evaluated by comparing the internal bond (IB) strength retention after five different laboratory-based accelerated aging tests with the IB retention after 5 years of outdoor exposure in Shizuoka City. In each accelerated aging test, the IB retention of MDI-bonded panels showed high retention compared to other panels. Outdoor exposure in Shizuoka City resulted in an IB retention value for particleboard (PF) and oriented strandboard (aspen) of less than 10% after the 5-year exposure period. Medium-density fiberboards maintained their initial IB strength over the same period. Calculation of the mean IB retention for all board types allowed comparison of the severity of aging between the accelerated test methods and outdoor exposure. The ASTM six-cycle test method was the most severe among the standard treatment cycles applied.     

Gas permeability of fiberboard mats as a function of density and fiber size

ABSTRACT

Gas permeability and structure of fiberboard mats are essential properties because of their impact on mat internal gas pressure, moisture content and temperature evolution during the hot-pressing process. The objectives of this work were to determine the effect of fiber size and mat density on the intrinsic gas permeability of the mat. For the study of these mat properties, panels with a homogeneous density profile through the thickness were manufactured at five density levels (200, 400, 600, 800 and 1000?kg m^?3) for three different fiber sizes. Fiber refining was performed in a disk refiner at three plate spacings. Gas permeability was measured with an in-house built apparatus. The results showed that the fiber sizes studied had no significant effect on the intrinsic permeability. This was likely due to a more significant impact of the internal porous structure of the mat compared to fiber size. Besides, the intrinsic permeability decreased significantly when the panel density increased from 198 to 810?kg m^?3. This suggests that the decrease of the intrinsic gas permeability during the last seconds of press closure plays an essential role in the bulk moisture mass transfer through the fiberboard mat.     

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.     

Simulation of a real-time process adaptation in the manufacture of high-density fibreboards using multivariate regression analysis and feedforward control

The industrial manufacturing of wood-based panels has become a highly technological process, where all parameters have to be perfectly adjusted to manufacture products of high quality. However, variations caused by differing wood characteristics as well as variations of single process parameters can cause out-of-control events. These undesirable events can be diminished by monitoring and controlling the entire manufacturing process using multivariate statistical techniques. Hence, a real-time process adaptation of an industrial scale fibreboard manufacturing process was simulated. Regression results revealed a mean normalised root mean squared error of prediction of 4.6 %, when predicting the internal bond strength of fibreboards. The regression model is regularly validated and, if necessary, recalibrated using the offline determined board properties (feedback control). Consequently, the process can immediately be adapted as soon as the board is produced (feedforward control). The investigations resulted in reliable models and revealed high potential for permanent industrial implementation.     

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.     

桦木顺纹抗压强度的SEPA-VISSA-RVM近红外光谱预测

木材顺纹抗压强度是评价木材力学性能的重要指标,而传统测量方法操作复杂、精确度低。以桦木为例,提出基于近红外光谱技术(NIR)的SEPA-VISSA-RVM木材顺纹抗压强度模型,实现对其更加精确的预测。试验选取100个木材试件,在900~1700 nm近红外光谱波段上采集数据并测量抗压强度真值;然后采用卷积平滑(SG)方法进行光谱预处理;使用采样误差分布分析(SEPA)作为变量空间迭代收缩算法(VISSA)的改进策略进行特征波长优选;最后通过粒子群优化算法(PSO)优化核函数参数并建立相关向量机(RVM)的预测模型。试验表明:在特征波长优选方面,以偏最小二乘法(PLS)建模为基础的SEPA-VISSA方法,其预测决定系数为0.9593,预测均方根误差为2.8995,相对分析误差为3.0256,光谱变量数由512减小到111个,占总波长的22%,均优于VCPA、CARS和VISSA算法;在建模预测方面,以SEPA-VISSA所选波长为基础的RVM模型,PSO优化的拉普拉斯(Laplacian)核函数的核宽度为10.4043,决定系数为0.9449,预测均方根误差为2.0432,相对分析误差为4.2936,预测效果优于PLS和SVR。因此,基于近红外光谱的SEPA-VISSA-RVM建模能够实现对桦木顺纹抗压强度更准确和稳定的无损检测。     

Estimating canopy closure density and above-ground tree biomass using partial least square methods in Chinese boreal forests

Boreal forests play an important role in global environment systems. Understanding boreal forest ecosystem structure and function requires accurate monitoring and estimating of forest canopy and biomass. We used partial least square regression (PLSR) models to relate forest parameters, i.e. canopy closure density and above ground tree biomass, to Landsat ETM+ data. The established models were optimized according to the variable importance for projection (VIP) criterion and the bootstrap method, and their performance was compared using several statistical indices. All variables selected by the VIP criterion passed the bootstrap test (p<0.05). The simplified models without insignificant variables (VIP <1) performed as well as the full model but with less computation time. The relative root mean square error (RMSE%) was 29% for canopy closure density, and 58% for above-ground tree biomass. We conclude that PLSR can be an effective method for estimating canopy closure density and above-ground biomass.