Wood blockboards for construction fabricated by wood welding with pre-oiled dowels

Holding wood pieces together by rotationally welded dowels can be used to make blockboard panels with the dowels inserted in the side of the wood substrate slats. Pre-oiling the dowels with sunflower oil: (i) eases their insertion in the pre-drilled substrate, (ii) allows the insertion of dowels to a much greater depth by its lubricating action for welding, thus allowing more layers of wood to be joined and (iii) provides an improved water resistance to the welded joint. The strength of the joints prepared with this system is comparable to those already obtained with other welded dowel systems but with improved water resistance.     

Wood bonding by mechanically‐induced in situ welding of polymeric structural wood constituents

Mechanically induced wood fusion welding, without any adhesive, is shown here to yield rapidly bonding wood joints satisfying the relevant requirements for structural application. The mechanism of mechanically induced vibrational wood fusion welding is shown to be due mostly to the melting and flowing of amorphous cells–interconnecting polymer material in the structure of wood, mainly lignin, but also some hemicelluloses. This causes a partial detachment, the “ungluing,” of long wood cells and wood fibers and the formation of an entanglement network drowned in a matrix of melted material which then solidifies, thus forming a wood cell/fiber entanglement network composite with a molten lignin polymer matrix. During the welding period some of the detached wood fibers which are no longer being held by the interconnecting material are pushed out of the joint as excess fiber. Crosslinking chemical reactions of lignin and carbohydrate‐derived furfural also occur. Their presence has been identified by CP‐MAS ¹³C‐NMR. These reactions, however, are relatively minor contributors during the very short welding period. Their contribution increases after welding has finished, which explains why relatively longer holding times under pressure after the end of welding contribute strongly to obtaining a good bond. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 243–251, 2004     

Investigations of mechanical properties and chemical changes occurring during welding of thermally modified ash wood

Abstract

Heat treatment of wood appears as an ecological and environmentally friendly alternative in the field of wood treatment. Generally, thermal modification increase dimensional stability by reduces of hygroscopicity and water absorption but it makes it difficult to bonding in some application. During welding, changes in the morphological, chemical, and physical properties of the wood cell wall are observed due to the compression and high temperatures produced by welding. Also, the degradation of cell wall in the wood causes some mechanical properties are reduced. This modification appears without any effect on the linear welding of thermal-ash wood. Scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) were used for evaluation of properties of wood–welding systems and their interactions. The mass spectrometry (MS) analysis was used to identifying the organic degradation products emitted during welding of thermo-ash. The results of experiments show that the use of friction welding for the bonding of thermal ash wood in dry conditions was possible, and we had good results. The best combination was with a welding time of 3.5?s devised to 0.5?s and 3?s and welding pressure 2.5 and 4?MPa, respectively. The result obtained is comparable to the result obtained with EPI adhesives. Welding time greater than 3.5?MPa negatively affects the welding quality and gives low the mechanical strength.     

高活性木炭的制备与孔结构表征

介绍了二步炭化法制备高活性木炭工艺。研究了保温时间和温度对活性木炭吸附性能的影响,并通过ESEM和HRTEM等对其孔结构进行表征。结果表明:二步炭化法可很好地提高木炭的性能,可制得孔径主要集中在0.6～2.0nm的活性木炭;随着保温时间延长,活性木炭的比表面积、孔容积均增大。在较佳实验条件下,所制高活性木炭的比表面积、总孔容积和微孔容积分别为1288.4m2/g、0.784mL/g、0.407mL/g。     

Optimization of beech wood pulping in catalyzed acetic acid media

Fagus sylvatica wood samples were treated in HCl‐catalyzed, acetic acid solutions. The effects of selected operational variables (catalyst concentration, reaction time and liquor to wood ratio) on pulp yield, composition of pulps and composition of pulping liquors were assessed using incomplete, second‐order, centred, factorial designs. Pulp composition was measured by the contents in cellulose, xylan and lignin. The concentrations of glucose, xylose and furfural in pulping liquors were also considered as experimental variables. Under selected conditions, pulps with 5.8% to 7.5% Klason lignin (kappa numbers in the range 25 to 33), 77.2% to 85.3% cellulose and 3.3% to 6.1% xylan were obtained at 45.8% to 50.0% pulp yield. The selected pulps showed good SCAN viscosity (723 to 814 mL/g) and alkaline resistances which were affected by the acetyl group content of samples (6.6 to 7.6 weight percent).     

塑料焊接加工几种方法

塑料应用于国民经济的各个领域,塑料制品光靠模具等一次性不能解决的,需要进行装配而成为可用的产品。由塑件变成可用的产品的过程中,有的需要塑料焊接加工,有的需要其他加工。本文阐述了热塑性塑料各种塑料焊接原理方法,介绍了塑料焊接应用方面的情况,旨在推广。     

PVC塑料门窗焊接工艺参数及其优化

焊接质量对PVC塑料门窗有重要影响,而焊接工艺参数的选择又是影响焊接质量的主要因素。     

Determination of optimal wood-dowel welding parameters for two North American hardwood species

Rotational wood-dowel welding has been shown to rapidly produce wood joints of considerable strength without any adhesive. The technique offers an opportunity to increase productivity and reduce costs in the furniture industry. The objective of the study was to define optimal wood-dowel welding parameters for two North American hardwood species frequently used for indoor appearance products: sugar maple (Acer saccharum) and yellow birch (Betula alleghaniensis). Optimized parameters for individually studied species were determined using a rotational wood-dowel welding machine designed for the technique. A comparative analysis of wood-dowel welding parameters was performed. The investigated parameters for both species were grain orientation, rotational speed, and insertion speed. Temperature profile measurements at the interface during rotational wood-dowel welding were also carried out. Optimal welding mechanical properties were determined from the dowel withdrawal strength using a standard tensile strength test. Results revealed a significant interaction between species, rotational speed, and insertion speed. Sugar maple produced wood joints with higher withdrawal strength than yellow birch. The best results for sugar maple and yellow birch were obtained with a rotational speed of 1000?rpm. A 25?mm?s^?1 insertion speed produced significantly stronger welded joints in sugar maple than at 12.5?mm?s^?1. For yellow birch, a 16.7?mm?s^?1 insertion speed provided the best results. Both species and rotational speed had a significant effect on peak temperature at the interface during welding. Peak welding temperatures with optimal parameters were 244 and 282?°C for sugar maple and yellow birch, respectively.     

二液型PU水性木器涂料的开发

介绍了二液型PU水性木器涂料的研究结果。二液型PU水性木器涂料是将带有氢氧基的乳液和特殊的异氰酸酯相结合而开发设计的产品,它不但具有与溶剂型涂料相当的优良性能,而且环保。主要用途是以木地板现场涂装为重点,其次也可以作为工厂生产家具及其它木器产品涂装用面漆使用。     

PVC木塑复合材料成型技术

介绍了废旧塑料再利用技术,探讨了PVC木塑复合材料的配方、工艺、制备及木粉的处理方法。结果表明:经处理的木粉,在PVC和木粉之间形成了较高强度的界面层,使木粉与基体树脂粘接力强,改善了材料的力学性能。     

改性PVB木材胶粘剂的研制

采用种子乳液聚合法制备聚丙烯酸酯乳液,再与松香改性PVB乳液混合制成复配木材胶,讨论了改性PVB乳液、保护胶体聚乙烯醇、乳化剂和引发剂的用量,以及丙烯酸酯类单体的配比、搅拌速度和反应温度等因素对胶粘剂性能的影响,得出了生产木材胶粘剂的最佳工艺。该胶粘剂具有水溶性好、初粘力大、粘接强度高、固化时间短等优点,显现出广阔的应用前景。     

Characterization of the ageing process of one-component polyurethane moisture curing wood adhesive

The aging resistance of five different one-component polyurethane (1C-PUR) adhesives with different mechanical properties has been investigated. The glue layer has been modeled as a superposition of three different layers representing the pure adhesive layer, the interaction layer between the wood and the adhesive and the plain wood layer. The modification of the mechanical properties of each layer was studied with a specific specimen for each layer. Also, a comparative analysis between natural and artificial weathering was conducted. The artificial weathering consists of a cyclic hydro-thermic treatment (treatment A5 according to DIN EN 302-1). The influence of a long time (5 months) mid-range temperature (70 °C) treatment was tested. Additionally, Fourier transform infrared spectroscopy (FTIR) analyses were conducted to determine the hypothetical chemical modification of the bond line. Generally, the strength properties of the samples decreased with the duration of the artificial weathering. However, significant differences were observed between the adhesive of the same system, especially during the temperature treatment. Furthermore, no relevant chemical degradation of the bond line was measured after 5 years of natural weathering (tested from 10 mm thick glued samples). The chosen method found that in the majority of cases, the wood is the weak layer in the bond line. Therefore, for moisture and temperature solicitation, there are no reasons to doubt the durability of the 1C-PUR glue layer for long term use. Nevertheless, further investigations are needed to better characterize the life expectancy of the wood and adhesive interface layer and to establish the influence of parameters, such as UV-radiation, wood extractives and moisture-induced stress, on the life expectancy of the bond line.     

木焦油改性生物油-酚醛树脂胶粘剂的工艺条件研究

以木焦油作为BOPF(生物油-酚醛树脂)的改性剂,制备BTPF(木焦油改性生物油-酚醛树脂)胶粘剂,并用于胶合板的制备。以木焦油加入量、催化剂(NaOH)含量和反应时间作为试验因素,以胶接强度、黏度和凝胶时间作为评价指标,采用正交试验法优选出制备BTPF胶粘剂的最佳工艺条件。结果表明:当w(木焦油)=15%、w(NaOH)=4%和反应时间为40 min时,BTPF胶粘剂的综合性能相对最好,并且完全满足GB/T 14732-2006标准中的指标要求,相应胶合板的胶接强度(1.54 MPa)和甲醛释放量(0.25 mg/L)达到了GB/T 18580—2001标准中的Eo级指标要求。     

水性木器涂料全封闭清漆着色涂装工艺探讨

介绍并比较了一些常见的水性木器涂料全封闭清漆着色工艺及涂装方法,并提出了一种新的面修色方法—专用修色漆修色法,弥补了常见修色方法的一些缺陷,克服了水性木器涂料全封闭清漆着色涂装的生产困难。     

Functionalization of wood particles through a reactive extrusion process

Wood particles were modified in a reactive extrusion process with maleated polyethylene (MAPE) and maleated polypropylene (MAPP) compounds. Contents of MAPE were varied to study the effect of material composition on grafting efficiency during reactive extrusion, while extruder barrel temperatures and rotational screw speeds were varied to evaluate the effects of processing conditions on the modification of wood particles. Polymer molecular weight effects were followed using MAPP, with different molecular weights. Efficiency of the modification was assessed using FTIR and XPS surface analysis techniques, along with a titrimetric analysis, to verify the esterification reaction between the wood particles and maleated polyolefins. The grafting of maleated polyolefins onto the surface of the wood particles through a reaction of the hydroxyl groups on the wood surface with the maleated groups of the maleated polyolefins was confirmed, while the level of grafting of MAPE onto wood particles was determined to be a function of the MAPE concentration. However, there was no significant difference found in grafting efficiency at different extrusion processing conditions, rather all of the conditions resulted in adequate grafting. Similarly, there was no difference in grafting efficiency with the molecular weight of MAPP. Reactive extrusion was found to be a suitable technique for the modification of wood particles, with maleated polyolefins, for all of the material compositions and processing conditions studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3131–3142, 2006     

纳米材料改性抗菌水性木器涂料的开发

介绍了纳米抗菌水性木器涂料的开发过程和施工工艺,分析讨论了其中的技术和问题。     

桉木枝桠材混合制浆性能实验

桉木是一种速生树种,其性能适合制浆造纸。实验将桉木按照一定比例均匀混入杨木枝桠材中进行磨浆,通过实验验证添加桉木后对制浆性能的影响。实验表明,桉木添加后浆料性能有所变化,消耗有所降低,桉木作为制浆原材料制浆能缓解制浆原料紧张,降低制浆成本,推广价值高,有很好的发展前途。     

IDENTIFICATION OF MATHEMATICAL MODEL COEFFICIENTS IN THE ANALYSIS OF THE HEAT AND MASS TRANSPORT IN WOOD

ABSTRACT

A method based on the concept of solving inverse heat and mass transport problems was proposed to identify wood physical properties, with the use of empirical data, a mathematical model corresponding to the direct problem, and an optimization procedure. The computer software was developed to solve transient, three-dimensional, quasi-linear direct and inverse problems of heat and mass transport in wood as an anisotropic body together with initial and boundary conditions of any kind. The software was adapted to data parallel processing environment of high performance computers. Identification of thermal conductivity was performed for beech wood in three principal anatomic directions, and accuracy of temperature distribution predictions was significantly increased (the global relative error of prediction was reduced to 1.0 - 1.9%).     

Influence of wood species on the properties of biopolyurethane prepared from liquefied wood with residue

Biopolyurethane prepared from liquefied wood with the residue of the liquefied wood product was investigated in this article. Previous results indicated that the residue of the liquefaction product was composed mostly of compounds originated from lignin. The chemical structures of lignin in softwood and hardwood are different. The influence of soft‐ and hardwood species on the chemical structure and mechanical properties of biopolyurethane prepared from liquefied wood with residue was investigated by tensile testing and Fourier transform infrared spectroscopy. The experimental results showed that the liquefaction of softwood occurs within a shorter time than that of hardwood and the biopolyurethane prepared from softwood was harder than that prepared from hardwood, which suggests that the properties of the liquefaction product and biopolyurethane are influenced by the chemical structure of the lignin. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010