紫茎泽兰对花生生长的影响及其经济阈值

为有效反映大田条件下紫茎泽兰对花生生长和产量的直接危害和经济危害允许水平,采用添加系列试验和模型拟合的方法研究不同紫茎泽兰密度下花生的生长和产量变化以及花生田间透光率和紫茎泽兰水肥积累量的变化。结果表明,花生在紫茎泽兰的竞争干扰下,花生荚果数、百仁重和果仁产量均随紫茎泽兰密度的增加而逐渐降低。花生荚果数和百仁重的降低可能是花生减产的直接原因。此外紫茎泽兰对田间透光率和对水肥的累积量的影响也可能是花生减产的重要原因。幂函数模型能较好地拟合紫茎泽兰密度（x）与花生产量损失率（y）间的关系（y=1.712x1.063,P〈0.0001）。花生田采用人工除草、草甘膦和氨氯吡啶酸对紫茎泽兰进行防除时,紫茎泽兰的经济危害允许水平分别为6.06%、0.57%、0.77%,经济阈值分别为3.28、0.36、0.46株.m-2。     

不同类型胶黏剂对难燃中密度纤维板燃烧性能的影响

采用异氰酸酯(MDI)、E₁级中密度纤维板用脲醛树脂(FU)和E₀级中密度纤维板用三聚氰胺改性脲醛树脂(MUF)制备难燃中密度纤维板,考察不同类型胶黏剂对难燃中密度纤维板阻燃性能的影响。结果显示,3种胶黏剂制备的难燃中密度纤维板的阻燃性能均达到了GB 8624—2012《建筑材料及制品燃烧性能分级》中B1级要求,MUF难燃中密度纤维板中三聚氰胺的存在对阻燃性能有提升作用,而MDI难燃中密度纤维板中MDI的易燃性降低了中密度纤维板的阻燃性能。     

自然霉变腐朽对中密度纤维板物理力学性能的影响

为了了解霉变腐朽对中密度纤维板物理力学性能的影响,研究自然条件下中密度纤维板物理力学性能在不同时期的变化。结果表明:自然霉变腐朽过程中,中密度纤维板的含水率先增加后减少;中密度纤维板的静曲强度、弹性模量、内结合强度、表面结合强度力学性能呈相同变化规律;中密度纤维板的力学性能中表面结合强度的下降幅度最大。     

利用紫茎泽兰制浆的可行性研究

对紫茎泽兰进行了化学成分及纤维形态分析;采用硫酸盐法和烧碱-蒽醌法对紫茎泽兰的制浆造纸性能做了初步探索。研究结果表明,两种制浆方法均能得到强度较好的纸浆,且浆料具有较好的可漂性,硫酸盐法浆的强度更好。     

中密度纤维板的力学性能与含水率关系研究

中密度纤维板的含水率是影响其力学性能的重要因素。通过在不同含水率条件下进行静曲强度、弹性模量和内结合强度试验,研究了中密度纤维板的力学性能与含水率之间的关系。结果表明:中密度纤维板含水率对其力学性能有显著的影响,通过平衡处理中密度纤维板的含水率从6.5%上升至14.0%,含水率每增加1%,静曲强度下降约9.6%,弹性模量下降约11.2%;内结合强度下降62.7%。     

湿度变化对MDF性能的影响

研究了薄木饰面及未饰面中密度纤维板（MDF）在不同湿度条件下的性能变化,结果表明：外界湿度的变化对各类中密度纤维板的性能均有影响;中密度纤维板经过薄木饰面后,其材长度方向的吸湿线膨胀率会有所降低,而厚度方向的吸湿膨胀率会略有增加。     

室外型中密度纤维板的研究现状与前景

中密度纤维板问世以来发展迅速,根据不同的用途发展了许多品种。室外型中密度纤维板具有优异的性能和广泛的应用领域,在国外已经处于工业化生产阶段,而在我国还处于研究开发阶段。国内外对室外型中密度纤维板的胶粘剂选用、制造工艺、使用性能等方面已经做了相当的研究,但在某些方面还有必要继续进行研究。室外型中密度纤维板有着良好的市场前景。     

入侵杂草紫茎泽兰的高光谱特征提取和分析

紫茎泽兰是一种世界性的入侵杂草,其对生态系统以及人类健康都有严重的危害。在西昌地区实地采集紫茎泽兰叶片,在室内利用ASD光谱分析仪进行高光谱数据提取,以此获取其原始光谱曲线,对光谱数据进行Savitzky-Glolay平滑滤波处理,然后利用包络线去除和一阶光谱微分法分析紫茎泽兰的光谱特征,旨在为紫茎泽兰的遥感识别提供参考依据。研究表明:紫茎泽兰667.00nm附近存在明显的吸收谷,其吸收谷面积为38.27nm~2,吸收深度为0.85nm,吸收宽度为74.00nm,中心吸收波段的左右面积呈现左偏移,吸收对称度为0.62,最大光谱吸收谷的特征波长的中心位置约为665.00nm。紫茎泽兰光谱一阶微分曲线的波峰位于725.00nm附近,由植被的"红边效应"引起;由于水的吸收作用,在1390.00nm和1880.00nm的近红外区域存在两个明显的波谷,可作为遥感识别紫茎泽兰的重要特征。     

几种成熟的胶粘剂生产工艺

一、中密度纤维板用低毒胶: 该胶是纯脲醛树脂胶,成本低,工艺条件简单,生产周期短,凡拥有制胶车间的中蜜度纤维板厂均可生产。用该胶生产出的中密度纤维物理力学性能指标能达到国家标准规定的一     

紫茎泽兰沼气发酵后作饲料喂养豚鼠的研究

毒性紫茎泽兰经预处理并沼气发酵后，能制成饲料，该饲料用于草食性动物豚鼠，５个月的实验表明，这种方式处理的紫茎泽兰已无毒性，这一研究为有毒植物的利用提供了可行之路。     

福建省几种竹材在纤维板工业上的利用研究

主要研究了用毛竹、绿竹、麻竹为原料制造中/高密度纤维板的工艺,通过正交法优选出了上述竹材制作竹或竹木质中/高密度纤维板的较佳工艺,用该工艺生产出来的纤维板产品的理化性能达到或超过了现行标准规定的技术指标.     

Virtual characterization of MDF fiber network

A virtual design method for medium density fiberboards (MDF) is proposed with the aim to optimize the fiber orientation and lay-up of MDF. The new method estimates the stiffness and strength by using microstructure models of the MDF fiber network. The virtual design is used to improve the manufacturing technology of MDF plates with multilayer oriented fiber structure. Experimental investigations of the mechanical behavior of MDF microstructure for various fiber geometries, glue content and distribution are complicated, time consuming and expensive. On the other side, virtual microstructure design allows to develop a new wood fiber based material with less experimental work. Microstructure models help to better understand the non-linear damage mechanical behavior of a wood fiber network depending on fiber geometrical parameters. Such parameters as crack distribution and fiber deformation on micro-scale level are complicated to experimentally measure, but possible to model using computer simulations. The virtual design tool requires less empirical data. The model takes into account information on average wood fiber orientation, fiber diameter, fiber length and mechanical properties of wood fiber cell wall and glue. The numerical method for strength and stiffness analysis of MDF microstructure was calibrated using standard MDF with non-oriented fibers. It turned out that this method gives precise results for MDF with oriented fibers and even with multilayer structure. The proposed virtual microstructure design tool can significantly improve and speed-up the optimization manufacturing technology of MDF and other wood fiber based composites.     

Die Bedeutung des Rohdichteprofils für MDF

The development of the MDF density profile is mainly influenced by the press control but also by the fibre condition (moisture, glueing). Although it was the target in the beginning of MDF manufacture to obtain a homogeneous density all over the board section, today's press control resp, technology practically allows the development of any density profile which can be optimally adapted to the individual application. Further, correlations between the density profile and some board properties are explained.     

意杨轻质中密度纤维板的研制

重点探讨了生产意杨轻质中密度纤维板时树种、纤维形态、纤维分离、施胶、热压等工艺因素对板材性能的影响,并对其成本及其经济效益进行了分析.结果表明开发意杨轻质中密度纤维板在技术上是可行的,而且具有显著的经济效益.     

Über die Eignung von thermo-mechanischem (TMP) und chemo-thermomechanischem (CTMP) Holzstoff aus Buchen- und Kiefernholz für die Herstellung von mitteldichten Faserplatten (MDF)

Medium density fibreboards (MDF) were made from thermomechanical (TMP) and chemo-thermo-mechanical pulps (CTMP) derived from pine wood. As a binder a melamine reinforced urea formaldehyde resin (UF-resin) and diisocyanate polymers (PMDI) were applied. The mechanical-technical properties of the boards as well as some of their chemical properties were evaluated. The results of the investigation led to the following conclusions: MDF from CTMP showed in general higher mechanical properties (bending strength) compared to MDF from TMP. Moreover, the formaldehyde release of the CTMP-boards was lower. This may be due to the formaldehyde scavenging properties of the used pulping chemicals during the process of CTMP. MDF from CTMP showed much higher release of acetic acid compared to MDF from TMP. This is likely to higher deacetylation of the wood substance during CTMP process compared to the TMP technique.     

The effect of Na+ montmorillonite (NaMMT) nanoclay on thermal properties of medium density fiberboard (MDF)

In this study, the potential use of nanotechnology was evaluated to improve the thermal properties of medium density fiberboard (MDF). For this, Na⁺ montmorillonite (NaMMT) nanoclay was added to urea formaldehyde resin to produce MDF. In order to characterize the structure of the MDF, X-ray diffraction (XRD) and SEM observation were performed, and the thermal properties were examined using thermogravimetric analysis (TGA), differential thermal analysis (DTA), thermal conductivity test and fire test. Characterization of the MDFs shows that dispersed and exfoliated structures were generated by the hot press. The X-ray diffraction confirmed the suitable exfoliation of NaMMT in the MDFs containing NaMMT. The SEM images of NaMMT-added boards showed a suitable dispersion of NaMMT through the MDF. The results of thermal tests indicated a desirable effect of NaMMT on thermal-oxidative stability and thermal conductivity of MDF.     

我国中密度纤维板机械制造技术的发展

通过介绍中密度纤维板生产线及其主机热磨机、热压机的技术进步,反映我国中密度纤维板机械制造技术的发展历程。     

Über die Eignung von thermo-mechanischem und chemo-thermo-mechanischem Holzstoff (TMP und CTMP) aus Buchen- und Kiefernholz für die Herstellung von mitteldichten Faserplatten (MDF)

Medium density fibreboards (MDF) were made from beech in laboratory and pilot plant scale from thermo-mechanical (TMP) and chemo-thermo-mechanical pulps (CTMP) using both melamine reinforced urea-formaldehyde resin (UF-resin) and diphenylmethane diisocyanate polymers (PMDI). The physicalmechanical and chemical properties of the boards were evaluated. From the results the following conclusions can be drawn:

1. Both TMP and CTMP led, on using UF-resin, to MDF with very high mechanical properties exceeding the required values in European standards.
2. Pulping temperature seems to have an influence on the mechanical properties of the boards, prepared from TMP and CTMP. Increasing the pulping temperature from 150°C to 170°C negatively affects the mechanical board properties, whereas the properties of MDF from CTMP (sulfonic group content between 0.2% and 0.3%) increases by elevating the maximum pulping temperature from 150°C to 170°C.
3. The pulping chemicals in the CTMP-process (Na₂SO₃ and/or NaOH) decrease the formaldehyde release from the boards, as they act as scavengers for formaldehyde.
4. Due to higher deacetylation degree during CTMP process, MDF made from CTMP release more than 4 times acetic acid than MDF from TMP. The release of formic acid is quite different, it is in MDF, made from TMP higher than in MDF from CTMP.
5. MDF with very high mechanical properties can also be made from beech pulps (TMP) using PMDI. PMDI in combination with a formaldehyde scavenger in the middle layer and UF-resin in the surface layer leads to boards with very low formaldehyde release.

     

Optimierung des Eigenschaftsprofils von MDF

During the last years, medium density fibreboards (MDF) became firmly established on the European wood-based material market. The production figures indicate that this tendency is still growing, although in some areas a certain saturation of the market has been reached. MDF manufactured in a dry process offering the possibility of producing such boards in comparable variety and quantity to particleboard, represent a panel product which is a serious competitor for the latter. In Germany, the MDF-production was taken over mainly by particleboard manufacturers. Thus, MDF was no more a competing product but a completion and an enlargement of the existing board range, especially in areas where the particleboard was only suitable for certain purposes. Due to its manufacturing process MDF distinctly differs from particleboard and for this reason reveils a different property profile. The user has not to deal with a substitute product offering “better properties”, therefore, he has to prepare himself for the product. The properties of MDF will be presented in detail and hints for the development of this product will be given.     

Vergleichende Untersuchungen an mittelharten Faserplatten (MDF) und Spanplatten

Mechanical and physical properties of commercial medium density fiberboard (MDF) and particleboard were determined and compared. The investigation showed that bending strength and face strength for MDF were considerably higher than corresponding particleboard properties. Concerning internal bond strength and screw holding ability no remarkable differences were found between the two board types. Medium density fiberboard showed lower hygroscopicity and thickness swelling but higher linear expansion than particleboard. Both board types were found to have higher bending strength and lower linear expansion parallel rather than perpendicular to feeding direction. Furthermore MDF showed lower surface roughness than particleboard.