中密度纤维板断面密度分布的控制

中密度纤维板断面密度分布的控制王凤鸣（北京市光华木材厂北京１０００２２）所有用干法生产的中密度纤维板（以下简称ＭＤＦ）的密度沿厚度方向的分布（以下简称断面密度分布）都是不均匀的。但这种不均匀并不是无规律的和不可控制。实践证明，生产者可通过采用正确的热...     

桉树中密度纤维板性能研究

为探讨桉树木材材性与中密度纤维板生产工艺的关系，进行了板材密度、施胶量与产品性能的研究。结果认为桉树中密度纤维板的密度以0.82g/cm     

中密度纤维板与异型面真空贴膜压机的发展前景

中密度纤维板与异型面真空贴膜压机的发展前景文／曹自力中密度纤维板具有密度适中，内部组织均匀，尺寸稳定性好，强度高，防腐性、抗虫蛀性能等优于木材，物理力学性能与机械加工性能优良，握钉力强，更接近于天然木材等一系列优点，因此，近年来成为发展最快的板材材种...     

大豆蛋白胶黏剂用于竹柳中密度纤维板试验

以大豆蛋白胶为胶黏剂,分别采用剥皮和未剥皮的竹柳枝桠材制备中密度纤维板.探讨了枝桠材树皮与木质部的比例和纤维得浆率,研究了树皮含量、施胶量和板材密度对竹柳纤维板物理力学性能的影响,优化了板材的制备工艺参数,并与脲醛树脂胶制备的剥皮竹柳中密度纤维板进行性能对比分析.结果表明:竹柳枝桠材的树皮含量这30.5％,其纤维得浆率比剥皮枝桠材低约4％;纤维板的性能随着密度和施胶量的增加而明显提高;剥皮竹柳所制纤维板的性能优于未剥皮的,未剥皮竹柳所制纤维板在密度为0.80 g/cm3,施胶量为16％时,其物理力学性能可满足GB/T 11718-2009的要求;而剥皮竹柳所制纤维板在密度为0.75 g/cm3,施胶量为14％时即可达到国标要求;大豆蛋白胶所制纤维极性能略低于脲醛树脂所制纤维板,但基本可以满足国标要求.     

耐盐竹柳中密度纤维板的研究

以耐盐竹柳为原料,对其进行纤维形态分析,并分别将剥皮竹柳纤维和不剥皮竹柳纤维试制中密度纤维板,探讨胶粘剂施加量和板材密度对纤维板弹性模量(MOE)、静曲强度(MOR)、内结合强度(IB)和吸水厚度膨胀率(TS)的影响。结果表明:密度和施胶量均对其性能指标具有显著的影响,板材性能随着密度和施胶量的增加而提高;剥皮的竹柳纤维制得的纤维板性能优于未剥皮纤维制得的板材;剥皮竹柳纤维制造的纤维板在板密度为0.75 g/cm3、施胶量为12%时,其物理力学性能指标MOE、MOR、IB、TS都达到了国家标准GB/T11718-2009的要求;而未剥皮纤维制得的纤维板在施胶量为14%、板密度为0.75 g/cm3时,其性能指标达到国家相关标准的要求;树皮对纤维板的物理力学性能有明显的影响。     

水玻璃胶黏剂在芦苇中密度纤维板中的应用研究

为了探索水玻璃胶黏剂在纤维板中的应用效果,以芦苇纤维和水玻璃胶黏剂为主要原料,制备了芦苇中密度纤维板,综合考察了密度、施胶量、活化剂用量对纤维板性能的影响。试验结果确定了芦苇中密度纤维板的较佳制备工艺为板材密度0.80 g/cm~3,施胶量为25.00%,活化剂量为5.00%,由此制备的芦苇中密度纤维板的各项物理力学性能达到GB/T 11718—2009规定的指标要求。     

干法低密度纤维板常规热压传热研究

采用常规热压方式对干法低密度纤维板进行热压传热研究,通过测定其热压过程中板坯中心层的温度,分析了热压温度、板坯含水率、板材厚度及板材密度与低密度纤维板中心层升温速度的关系,得出了干法低密度纤维板常规热压传热的基本规律。     

竹柳枝丫材与小径材中密度纤维板的研究

以竹柳枝丫材和3年生小径材为原料,采用脲醛树脂胶分别制备中密度纤维板。对比分析枝丫材与3年生小径材的密度、化学成分、纤维得浆率和纤维形态,研究施胶量和板材密度对竹柳纤维板物理力学性能的影响。结果表明:竹柳枝丫材的密度小于小径材的密度;竹柳枝丫材与小径材均有较高的综纤维素含量;竹柳枝丫材的纤维得浆率低于竹柳小径材;竹柳枝丫材、小径材纤维的壁腔比均小于1,是良好的纤维原料;竹柳枝丫材与小径材所制板材的性能均随着密度和施胶量的增加而明显提高;竹柳枝丫材所制纤维板的性能略低于小径材的,竹柳枝丫材所制纤维板在密度为0.75g/cm~3,施胶量为14%时,其物理力学性能可满足GB/T 11718—2009的要求;而竹柳小径材所制纤维板在密度为0.70g/cm~3,施胶量为14%时即可达到国标要求。     

室外自然老化对人造板材物理力学性能的影响

给出了对中密度纤维板、胶合板等人造板材进行室外自然老化性能试验数据，即通过对放置在室外１￣２年的上述人造板材和各项物理力学性能的测试，进一步分析了室外自然老化对人造板材物理力学性能方面的影响及其产生原因，这项试验对今后人造板的生产与使用等方面，都具有十分重要意义。     

无胶蔗渣纤维板制备及性能

以蔗渣纤维为原料,通过热压成型工艺制备了无胶蔗渣纤维板。研究了板材密度、热压温度以及热压时间对其物理力学性能的影响,并通过傅里叶红外光谱及X射线衍射等分析了板材成型机理。结果表明:随着板材密度、热压温度以及热压时间的增加,无胶蔗渣纤维板静曲强度、弹性模量、内结合强度逐渐增大,2h吸水厚度膨胀率逐渐减小。热压过程中,蔗渣纤维中的纤维素和半纤维素基环甙键产生裂变,部分木素降解,产生活性羟基并在纤维间形成氢键,同时,蔗渣纤维中的半纤维素发生水解,生成起胶合作用的缩聚呋喃树脂。热压温度升高,活性羟基及氢键数量增加,缩聚呋喃树脂生成量增大,无胶蔗渣纤维板力学性能更好。     

木材树种对刨花/EPS泡沫复合轻质刨花板性能的影响

为实现刨花板轻量化,通过向芯层引入聚苯乙烯(EPS)泡沫颗粒,制备平均密度为500 kg/m^3的刨花板,探索表芯层刨花构成对板材的剖面密度分布和物理力学性能的影响。结果表明:以杨木细刨花为表层、桉木粗刨花和EPS泡沫颗粒混合物为芯层制备的复合轻质刨花板,其表芯层密度差异最为显著,力学性能达到GB/T 4897-2015《刨花板》中干燥状态下使用的家具型(P2型)刨花板的要求。     

热压桦木木粉块剖面密度分布的研究

为制备高性能的SiC陶瓷,以桦木木粉为原料,采用无胶热压成型工艺制备木粉块。研究木粉含水率、热压温度、合模方式及木粉块密度对剖面密度分布的影响,探讨剖面密度分布的形成机理,获得制备剖面密度均一分布木粉块的优化工艺条件。     

基于CT技术的人造板剖面密度检测

利用CT技术无损检测槐树大片刨花板、柳杉重组木以及麦秸中密度纤维板的内部结构与密度特征。结果表明:大片刨花板与重组木的密度变异均高于麦秸板;大片刨花板剖面密度分布无明显变化规律,而重组木呈W型分布、麦秸板呈V型分布。CT技术将为深入研究木基复合材料的结构与性能产生积极影响。     

黄土高原油松人工林根系改善土壤物理性质的有效性模式

在调查根系参数和测定土壤物理性质的基础上,首先对油松人工林不同深度根系对土壤物理性质的改善效应及其与根系相互作用的关系进行了定量分析。结果表明,根系改善土壤物理性质的效应与有效根密度(≤1mm的须根)在剖面中的分布规律一致,均呈指数递减规律,其垂直变化可分为四个明显区域,土壤物理性质改善效应与≤1mm的须根密度(即有效根密度)比与根量的关系更为密切,在P<0.001极显著水平上呈线性正比关系。据此建立了油松人工林根系改善土壤物理性质的有效性模式。     

剖面密度测定与人造板质量控制

在人造板生产过程中,板材的剖面密度分布直接影响板材的物理力学性能,同时也关系到企业的生产成本,因此准确地测量并分析板材的剖面密度分布,进而调整各项工艺参数,是企业提高产品质量、降低生产成本的重要方法.     

木质人造板剖面密度分布的意义与研究进展

剖面密度分布是木质人造板重要的结构特征，也是影响其物理力学性能的重要因素之一，本文论述了剖面密度分布与人造板性能的关系，影响剖面密度分布的主要工艺因素和为获得预期剖面密度分布而采用的工艺调控措施，最后综述了计算机模拟技术在木质人造板剖面密度分布研究中的应用和最新进展。     

Spatial distribution of Eucalyptus roots in a deep sandy soil in the Congo: relationships with the ability of the stand to take up water and nutrients

Spatial statistical analyses were performed to describe root distribution and changes in soil strength in a mature clonal plantation of Eucalyptus spp. in the Congo. The objective was to analyze spatial variability in root distribution. Relationships between root distribution, soil strength and the water and nutrient uptake by the stand were also investigated. We studied three, 2.35-m-wide, vertical soil profiles perpendicular to the planting row and at various distances from a representative tree. The soil profiles were divided into 25-cm2 grid cells and the number of roots in each of three diameter classes counted in each grid cell. Two profiles were 2-m deep and the third profile was 5-m deep. There was both vertical and horizontal anisotropy in the distribution of fine roots in the three profiles, with root density decreasing sharply with depth and increasing with distance from the stump. Roots were present in areas with high soil strength values (> 6,000 kPa). There was a close relationship between soil water content and soil strength in this sandy soil. Soil strength increased during the dry season mainly because of water uptake by fine roots. There were large areas with low root density, even in the topsoil. Below a depth of 3 m, fine roots were spatially concentrated and most of the soil volume was not explored by roots. This suggests the presence of drainage channels, resulting from the severe hydrophobicity of the upper soil.     

Effects of density profile of MDF on stiffness and strength of nailed joints

Nail-head pull-through, lateral nail resistance, and single shear nailed joint tests were conducted on medium density fiberboard (MDF) with different density profiles, and the relations between the results of these tests and the density profiles of MDF were investigated. The maximum load of nail-head pull-through and the maximum load of nailed joints were little affected by the density profile. However, the ultimate strength of lateral nail resistance, the stiffness, and the yield strength of nailed joints were affected by the density profile of MDF and showed high values when the surface layer of the MDF had high density. It is known that bending performance is also influenced by density profile. Therefore, the stiffness and the yield strength of nailed joints were compared with the bending performance of MDF. The stiffness of nailed joints was positively correlated with the modulus of elasticity (MOE); in the case of CN65 nails, the initial stiffness of joints changed little in response to changes in MOE. The yield strength of nailed joints had a high positive correlation with the modulus of rupture (MOR). The stiffness and the yield strength of nailed joints showed linear relationships with MOE and MOR, respectively.     

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     

Vertical distribution of fine root density, length density, area index and mean diameter in a Quercus ilex forest

We used minirhizotrons to determine the vertical distribution of fine roots in a holm oak (Quercus ilex L.) forest in a typical Mediterranean area over a 3-year period (June 1994-March 1997). We measured fine root density (number of roots per unit area), fine root length density (length of roots per unit area), fine root area index (area of roots per unit area) and fine root mean diameter. Variables were pooled for each 10-cm depth interval to a depth of 60 cm. Fine roots tended to decrease with increasing depth except between 0 and 10 cm, where the values of all fine root variables were less than in the 10-cm stratum below. Fine root vertical distribution was compared with soil water content and soil temperature at different depths in the soil profile.