等离子体改性热塑性树脂薄膜制备环保胶合板试验

为获得无甲醛释放的环保胶合板,将热塑性树脂薄膜(低密度聚乙烯(LLDPE)、聚丙烯(PP)、聚氯乙烯(PVC))用作胶黏剂,并利用空气介质阻挡等离子体对热塑性树脂薄膜进行表面改性处理以提高薄膜与杨木单板的界面相容性,从而获得性能良好的环保胶合板。研究了等离子体处理对胶合板胶合性能的影响,并从等离子体处理对热塑性树脂薄膜表面化学组分及其对胶合板界面形貌的影响分析其胶合机理。结果表明:在等离子体处理功率为4.5 kW、处理时间为8 m/min的条件下处理热塑性树脂薄膜,胶合板的胶合强度得到显著提高,LLDPE/杨木胶合板的胶合强度从0.49 MPa增至0.81 MPa,PP/杨木胶合板的胶合强度从0.65 MPa提高到0.84 MPa,均达到Ⅱ类胶合板标准要求。其中用等离子体处理后PVC与杨木制备的胶合板能满足Ⅰ类胶合板的标准要求,胶合强度达到0.79 MPa。XPS分析表明,等离子体改性热塑性树脂薄膜的表面发生了氧化反应,引入了含氧官能团,提高了薄膜表面极性,有利于提高薄膜与杨木单板之间的相互作用,从而使得胶合板的界面胶合更为紧密,说明等离子体处理后树脂与杨木单板的相容性提高,树脂能在单板表面更好地附着。热塑性树脂薄膜与杨木单板制备的胶合板仅有极微量甲醛释放,其主要源于木材自身,远低于国家标准对人造板甲醛释放限量的要求。研究证明等离子体处理能明显改善热塑性树脂薄膜与杨木单板的界面相容性。     

Properties of red maple laminated veneer lumber impregnated with waterborne micronized and two soluble copper formulations

ABSTRACT

Certain important quality parameters of red maple (Acer rubrum) laminated veneer lumber (LVL) impregnated with three waterborne formulations: copper azole (CA-B), micronized copper azole (MicroCA or MCA) and alkaline copper quaternary (ACQ-D) bonded with phenol formaldehyde or cross-linked polyvinyl acetate (XPVAc) adhesives were evaluated. Pre-dipping of veneers before LVL production and two post-manufacturing procedures, viz., vacuum-pressure and post-dipping of LVL, were applied. Maximum copper retention in pre-dip-treated, vacuum-pressure and post-dip-treated LVL was 1.4, 9.7 and 1.7?kg/m³, respectively. Copper retention in MCA-treated LVL was relatively lower than soluble formulations. Various physical, mechanical and bonding properties of treated LVL such as density, water absorption, swelling, flexural properties, hardness, tensile shear strength, delamination and wood failure (%) were studied and compared with untreated LVL. Little to negligible deleterious effect was observed on properties of LVL due to these chemical treatments. Analysis of variance results showed that most of properties of red maple LVL were not significantly different compared with those of untreated LVL. Therefore, vacuum-pressure impregnation process can be used to treat the red maple LVL with novel micronized copper formulations for increasing the service life of such products against biodegradation without affecting techno-mechanical quality parameters.     

Effect of the addition of <Emphasis Type="Italic">Acacia mangium</Emphasis> bark on thermosetting of phenol–formaldehyde resin

The effect of addition of Acacia mangium bark powder on the thermosetting processes of two commercial phenol resins, PF-A and PF-B, was examined by bond strength test, torsional braid analysis, and differential scanning calorimetry. When the bark powder was added to PF-A, the bond strength of plywood pressed at 110°C increased and was comparable to that of plywood pressed at 120 and 130°C. However, when the bark powder was added to PF-B, the bond strength of plywood pressed at 110°C was still lower than that of plywood pressed at 120 and 130°C. The relative rigidity and loss tangent of PF-A cured with the bark powder obtained by heating at 100°C were comparable to those at 120 and 140°C, and the reaction enthalpy was increased by bark powder addition. In contrast, chemical reactions for cured PF-B were not enhanced by bark powder addition.     

国外结构人造板研究现状与发展趋势

本文介绍了国外新型结构人造板的研发现状，重点介绍了胶合层积木、单板层积材等主要结构人造板的工艺过程、基本性能和相关标准。     

A review of the utilisation of hardwoods for LVL

This review on the use of hardwoods for the production of LVL revealed that a large number of research studies have been carried out, particularly in North America and three Asian countries (Japan, Malaysia and China). However, the studies have been restricted to species of low to medium density, i.e. 290 to 693 kg/m³. Two major potential uses of hardwood LVL have been investigated in these studies: domestic and industrial structures, and various furniture components. The production of structural LVL in North America and Asia was based predominantly on low density hardwoods. A study currently carried out in Europe aims at using medium density hardwoods for structural LVL. The LVL used for furniture components was produced from medium density hardwoods. No work has been undertaken outside Australia on the use of high density species for LVL. In Australia, studies undertaken on the production of LVL and hardwood plywood from eucalypts revealed that there were significant problems in gluing the dense raw material which often had a high level of extractives. Peeling low quality, small diameter eucalypt logs also created problems when the traditional plywood processing techniques were used. Received 7 July 1997     

Study on sheet material made from zephyr strands V: Properties of zephyr strand board and zephyr strand lumber using the veneer of fast-growing species such as poplar

Zephyr strand board (ZSB) and zephyr strand lumber (ZSL) were produced using zephyr made from poplar veneer to investigate the greater utilization of low-density poplar as a structural material. These materials were then compared to ordinary plywood, laminated veneer lumber (LVL) from poplar veneer, lauan plywood, and particleboard. The bending properties (moduli of rupture and elasticity) of ZSB proved superior to those of poplar plywood: and ZSL produced from poplar veneer zephyr had bending properties greater than ordinary LVL from poplar veneer. Apparently, the conversion of the poplar veneer into zephyr material had a positive effect on bending properties. Additionally, poplar ZSB had bending properties superior to those of lauan particleboard and equal to those of lauan plywood. The internal bond strength of poplar veneer ZSB was nearly two times greater than that of lauan particleboard.Parts of this report were presented at the international symposium on the utilization of fast-growing trees, Nanjing, China, October 1994. Report IV appeared inMokuzai Kogyo 49:599, 1994     

Comparative study on physical and mechanical properties of laminated veneer lumber and plywood panels made of wood from fast-growing <Emphasis Type="Italic">Gmelina arborea</Emphasis> trees

Laminated products, such as laminated veneer lumber (LVL) or plywood (PW), have become important recently. The objective of this study was to determine and compare properties of panels fabricated with veneers of Gmelina arborea trees in a fast-growth plantation and glued with phenol formaldehyde resin. The results showed that LVL and PW physical and mechanical properties are comparable to those of solid wood with a specify gravity of 0.60. Moreover, these panels can be cataloged into group 2 of PS 1–95 of the Voluntary Products Standard of the United States. The difference in physical properties was not statistically significant between LVL and PW panels, except for water absorption. Some mechanical properties, such as hardness and glue-line shear, modulus of rupture in perpendicular flexure, nail and screw withdrawal parallel, and perpendicular strength, were statistically different between LVL and PW. However, no differences were established for the modulus of elasticity, tensile strength parallel to the surface, or tensile strength perpendicular to the surface. The differences were attributed to the venners’ orientation in the panels studied.     

年产5000m3意杨LVL主材及设备量的计算与配置

LVL已成为当今木材加工行业发展速度最快的一种木质复合材料产品.介绍了苏北一家年产5000m3意杨LVL企业的加工材料与设备配置情况,着重对单板、胶黏剂主材及压机等主要设备进行了相关的设计计算与配置,为我国制造胶合板的中小型企业做好意杨LVL产品的主材及其设备的设计工作提供参考.     

三种三聚氰胺改性脲醛树脂胶结构与性能关系的研究

用IR、~(13)C-NMR、TG等仪器分析手段结合化学分析对三种三聚氰胺含量不同和F/(U+M)摩尔比不同的MUF树脂的化学结构和性能之间的关系进行研究。发现MUF树脂的固化时间与其羟甲基含量有关。用MUF树脂压制的杨木胶合板的强度与其三聚氰胺量和羟甲基含量有关。杨木胶合板的甲醛释放量与MUF树脂的羟甲基含量和亚甲基醚键含量有关。     

Effect of an oil heat treatment on the teachability and biological resistance of boric acid impregnated wood

Vegetable oils provide boron retention of about 30% of initial amount depending on oil drying properties. Linseed oil is the most efficient, followed by soybean oil and rapeseed oil. Durability of C. japonica and F. crenata wood specimens has been enhanced by application of linseed oil alone but not enough to reduce termite’s attack of Coptotermes formosanus. Treating wood with a 1.0% w/w boric acid solution prior to oil treatment protects C. japonica from termite and fungi degradations. Efficiency against termites is mainly due to boron retention by oil but hydrophobic oil also forms a barrier decreasing fungi penetration. Boron efficacy threshold around 0.7 kg/m³BAE, lower than classical boron treatments thresholds indicates that oil water-repellence reinforces boron biostatic effect.     

The effect of elevated temperature exposure on the fracture toughness of solid wood and structural wood composites

Fracture toughness of wood and wood composites has traditionally been characterized by a stress intensity factor, an initiation strain energy release rate (G _init) or a total energy to fracture (G _f). These parameters provide incomplete fracture characterization for these materials because the toughness changes as the crack propagates. Thus, for materials such as wood, oriented strand board (OSB), plywood and laminated veneer lumber (LVL), it is essential to characterize the fracture properties during crack propagation by measuring a full crack resistant or R curve. This study used energy methods during crack propagation to measure full R curves and then compared the fracture properties of wood and various wood-based composites such as, OSB, LVL and plywood. The effect of exposure to elevated temperature on fracture properties of these materials was also studied. The steady-state energy release rate (G _SS) of wood was lower than that of wood composites such as LVL, plywood and OSB. The resin in wood composites provides them with a higher fracture toughness compared to solid lumber. Depending upon the internal structure of the material, the mode of failure also varied. With exposure to elevated temperatures, G _SS for all materials decreased while the failure mode remained the same. The scatter associated with conventional bond strength tests, such as internal bond and bond classification tests, renders any statistical comparison using those tests difficult. In contrast, fracture tests with R curve analysis may provide an improved tool for characterization of bond quality in wood composites.     

Tensile strength of thermally modified laminated strand lumber and laminated veneer lumber

Laminated strand lumber (LSL) and laminated veneer lumber (LVL) were thermally modified as a post-treatment at 140°C, 150°C, 160°C, 170°C, and 180°C. The tension modulus of elasticity (MOE) of LSL was not significantly impacted by the treatments, with the 180°C treatment group exhibiting the highest tension MOE (11.8?GPa). The LVL also experienced minimal impacts, with the 150°C treatment group having the highest tension MOE (19.4?GPa) and the 160°C treatment group exhibiting the lowest (17.1?GPa). The maximum tensile strength (MTS) of the LSL and LVL significantly decreased with increasing temperatures, with the control and 180°C treatment groups experiencing the highest and lowest MTS, respectively. The lowest MTS for LSL was 10.8?MPa (180°C treatment), which was 70% lower than the controls. The lowest MTS of the LVL was 24.4?MPa (also at the 180°C treatment), which was a 49% decrease compared to the controls. These results suggest that thermal-modification post-treatments minimally impact tension MOE, but can significantly reduce MTS at higher treatment temperatures. Combined with previous work improving the moisture properties and equilibrium moisture content of thermally modified LSL and LVL, it may be possible to optimize the treatment technique(s) to yield products with desirable properties.     

竹片覆面胶合板的初步研究

本文研究了以竹片为外层材料、多层杨木单板为芯层材料的复合胶合板的结构和力学性能，分析了板坯结构形式、纵向纵片厚度、单板层数及板坯压缩率与产品机械强度之间的关系。初步研究结果表明，板坯结构形式对产品的静载荷抗弯曲性能影响显著；在试验范围内，纵向竹片厚度为３．５－５．０ｍｍ、板坯压缩率在２３％左右时，竹片覆盖面杨木胶合板的综合力学性能比较理想。     

竹板增强单板层积材组合梁受弯性能

单板层积材加工成梁构件应用于建筑结构材时,由于材料本身的强度和刚度不足,其结构构件不能满足现代多、高层以及大跨度建筑的需求。竹集成材是原竹经过切削成竹片、低温干燥、碳化、涂胶,再同方向平面或侧面组坯、热压胶合而成的竹基复合材料,其力学性能与稳定性优于木材。将集成竹材作为增强材料用于加固单板层积材梁是一种简单有效的提高梁极限承载力的方法。通过进行竹板增强单板层积材组合梁四点弯曲试验,研究了集成竹板对单板层积材受弯性能的增强效果。结果表明,在单板层积材受弯构件上下部粘贴集成竹板可提高构件极限承载力10%～50%。同时,考虑单板层积材和集成竹材料的非线性,推导出了适用于组合梁的极限承载力计算公式,计算结果与试验结果吻合良好。     

利用响应曲面法优化脲醛树脂合成工艺

使用响应曲面法研究尿素添加次数和尿素添加时间间隔对脲醛树脂性能和其板材性能的影响,使用傅里叶红外光谱仪定性分析尿素添加次数和尿素添加时间间隔对脲醛树脂主要基团的影响。结果表明:尿素添加次数和尿素添加时间间隔对脲醛树脂的固体含量及固化时间影响不大,而对黏度、树脂中羟甲基含量、游离甲醛含量、各主要基团含量和板材的性能有很大影响。树脂合成工艺中2次添加尿素,间隔时间20min时,树脂和板材性能比较好。     

PEI/APP改性脲醛树脂制备阻燃胶合板及性能

以聚乙烯亚胺(PEI)为改性剂处理聚磷酸铵(APP)制备得到APP@PEI阻燃体系,并将其加入到脲醛树脂(UF)中,制备阻燃胶合板.研究了APP@PEI对UF胶黏剂理化性能的影响,并进一步探讨其对胶合性能及阻燃性能的影响.结果表明:APP、PEI和APP@PEI对UF的黏度、pH和固化时间均有影响.当APP添加量为10...     

Effects of fire-retardant treatment and wood grain on three-dimensional changes of sandwich panels made from bubinga decorative veneer

ABSTRACT

The effects of a fire-retardant treatment (FRT) and wood grain on three-dimensional changes of aircraft sandwich panels were evaluated. Unvarnished and varnished panels having the outer decorative layer made with bubinga (Guibourtia spp.) were studied. Half of the samples from each type of panel received an FRT (phosphate-based) on all three layers of the decorative plywood. The other half had the two inner layers treated and the outer layer untreated. Three different figures formed by the rotary cutting and grain orientation were identified and separately studied on veneer surfaces. Samples pre-conditioned to 20°C and 40% relative humidity (RH) underwent an adsorption (25°C, 90% RH) and then a desorption (25°C, 40% RH) treatments. Changes in moisture content (MC), swelling, shrinkage, roughness, and waviness were measured after each moisture exposure condition. The results showed that the FRT increased significantly MC, swelling, and shrinkage of unvarnished and varnished panels. This treatment as well as the type of wood figure affected roughness and waviness variations of unvarnished panels. However, the effects of these two factors were not noticeable once panels were varnished.     

轻型木结构用落叶松胶合板覆板均布载荷性能试验研究

介绍了轻型木结构覆板均布静载结构性能试验的装置、条件和方法，并进行了国产落叶松胶合板制作轻型木结构覆板的均布静载性能研究。结果表明：与国外胶合板覆板具有相同厚度的国产落叶松屋面板和楼面板，其均布载荷性能均优于标准规定的技术指标值。     

微纳纤丝改性豆胶制造染色杨木胶合板

将不同微纳纤丝添加量的三聚氰胺树脂涂饰在杨木单板表面,并以添加微纳纤丝的豆胶作为胶黏剂,制造杨木胶合板,检测微纳纤丝添加量对染色杨木单板表面色牢度、胶合板表面耐磨性能、胶合强度的影响。结果表明:微纳纤丝可明显改善单板表面色牢度及表面耐磨性能;在豆胶中加入微纳纤丝,可提高胶合板的胶合强度。     

Effect of loading frequency on fatigue life and dissipated energy of structural plywood under panel shear load

Wood-based panels are subjected to cyclic panel shear load caused by wind and seismic forces in such an application as the sheathing of bearing walls. The fatigue behavior of structural plywood under panel shear load with two different loading frequencies was examined. Pulsating panel shear load with a triangular waveform and loading frequency of 0.5 or 5 Hz was applied to the plywood specimens. Stress−strain hysteresis loops were measured throughout the fatigue tests. Fatigue life was highly dependent on loading frequency at more than 0.5 stress level. The deterioration of mechanical property and damage accumulation in plywood specimen was observed to be slower at higher loading frequency at more than 0.5 stress level. Analyses based on energy loss suggest that panel shear load with higher loading frequency causes less damage to the plywood specimen during one loading cycle at higher stress level, and that the fatigue damage accumulation causing failure might be dependent on stress level although it seems to be unaffected by loading frequency. Based on these results, a new fatigue failure model for plywood specimen was qualitatively developed by combining Weibull’s weakest link model and Daniels’ fiber bundle model.