弯曲木材试件尺寸稳定性与陈放时间的关系

研究了不同软化工艺条件下,弯曲木材试件的尺寸稳定性与陈放时间的关系。试验结果表明:不同的软化工艺条件对应不同的陈放时间。在软化条件Ⅰ下,陈放时间为4h,试件获得比较好的尺寸稳定性;在软化条件Ⅱ下,6h为一个相对合适的陈放时间;在软化条件Ⅲ下,试件在陈放6h之后,能达到比较好的效果。     

水热-微波处理木材软化效果模型构建

水热-微波联合软化既能使木材在湿热作用下降低木质素的玻璃态转化温度,又能在微波照射下消除木材内部的温度梯度缩短软化时间,使木材快速达到较好的软化效果。采用水热-微波联合处理的方法对具有一定密度梯度白木香(Aquilaria sinensis)、人工林柚木(Tectonagrandis)、西南桦(Betula alnoides)、天然林柚木(Tectonagrandis)、柠檬桉(Eucalyptus citriodora)进行软化处理并迅速对5种木材的弯曲挠度进行测定,构建这5种木材弯曲挠度y与密度x_1、水热温度x_2、水热处理时间x_3、微波功率x_4、微波照射时间x_5工艺参数的软化模型。所建模型为y=34.442-46.382*x_1+0.08497*x_2+0.02827*x_3+0.01856*x_4+0.0302*x_5(R~2=0.9015),模型中各影响因子权重中密度影响最大,其次是水热温度、微波照射时间、水热处理时间、微波功率。通过实验发现,人工林柚木与天然林柚木在110℃的湿热条件下内含物就已经开始降解,苯-醇抽出物含量从未处理时的7.12%减小为6.32%。为了既能保持柚木的尺寸稳定性又能使柚木达到较好的软化效果,利用软化模型获取适合柚木的软化工艺:水热温度110℃、蒸汽处理时间为240min、微波功率600W、微波照射时间4.5min。     

弯曲木构件浸水后回复蠕变的初步研究

回复蠕变影响弯曲木构件的尺寸稳定性,探索弯曲木构件回复蠕变与浸水时间的关系对研究曲木家具有重要意义。通过水热处理软化水曲柳、枫木和橡胶木试件,利用弯曲模具制造弯曲木构件。试验结果表明,弯曲木构件的回复蠕变与浸水时间呈正相关关系。不同树种,或同一树种不同水热处理工艺,试件回复蠕变均随其浸水时间的延长而增加。     

木材的软化处理与弯曲技术

根据木材弯曲的原理、弯曲技术以及木材软化处理的一些方法，介绍生产弯曲零部的工艺过程。     

三种弯曲木的吸湿回弹及影响因素

实木弯曲是生产木质弯曲构件的重要方式,弯曲木的吸湿回弹影响尺寸稳定性以及产品质量。为研究弯曲木的吸湿回弹行为,软化处理、干燥定型弯曲木,在25℃室温条件下,调整湿度、弯曲直径和材料尺寸数值,以质量、宽度、厚度、弦长、拱高对弯曲木的经时吸湿回弹行为进行表征,发现随湿度增大,质量、尺寸、形状达到稳定时间延长,与湿度非正相关;弯曲直径对质量、宽度、厚度影响区别不大,对弦长、拱高影响明显,回弹量与弯曲直径非线性负相关;不同尺寸的弯曲木吸湿回弹稳定时间差异明显,尺寸增大,吸湿曲线稳定时间延长。弯曲木吸湿回弹影响最大的是环境湿度和弯曲直径。     

超临界温度氨软化处理杨木单板初探

以氨水为软化剂,以杨木单板为材料,采用氨的超临界温度的软化方法,着重探讨了温度、时间和单板厚度对软化效果的影响,通过顺纹弯曲的弯曲性能表征木材软化效果。结果表明:超临界温度氨的软化温度、时间和单板厚度对木材的弯曲性能均有一定的影响,在本研究中,最佳的软化条件:温度为140℃,时间为100min,单板厚度为1mm。     

卤水——氨法碱式氯化镁晶须的制备及影响因素的研究

在常压下用液相反应法制备了碱式氯化镁晶须，研究了氯化镁浓度、氯化镁与氨水的摩尔比、反应温度、陈化温度、陈化时间对碱式氯化镁晶须制备的影响。根据XRD和SEM测试结果，提出了制备碱式氯化镁晶须的最佳工艺条件：（1）氯化镁浓度为3mol／l；（2）氯化镁与氨水的摩尔比为4：1～6：1；（3）最佳反应温度为30℃；（4）氨水的加料速度为10ml／min～20ml／min；（5）最佳陈化温度为50℃～60℃，最佳陈化时间为48h～72h。制备得到了长径比≥100碱式氯化镁晶须。     

黑曲霉液态发酵陈化稻米生产柠檬酸的研究

研究了接种量、发酵温度与时间、氮源等因素对以陈化稻米为原料,黑曲霉液态发酵法生产柠檬酸的影响,并优化了工艺。结果表明,陈化稻米粉碎后,经α-淀粉酶液化得到合适的发酵培养基,液态发酵柠檬酸的优化工艺为：初始培养基pH值为4、加1％氯化铵、接种量1％、发酵温度34 、发酵时间96h,产酸率最高可达到13．1％。本研究为可陈化稻米的深度开发提供途径。     

4种珍贵阔叶树材尺寸稳定性处理技术

采用三聚氰胺改性脲醛树脂,一缩二丙二醇（DPG）,α-桐甲脂3种药液为主剂,加入不同的助剂,对铁木豆、黑皮黄杨、牛筋木、红豆丝4种珍贵阔叶树材进行浸渍处理。探讨了不同药液及其配比对提高木材尺寸稳定性的作用。结果表明：以该3种药液为主剂的改性处理剂都能起到提高木材尺寸稳定性的作用,但是不同树种、不同药液处理效果不同。     

浅析曲木工艺中的蒸煮软化机理

在我国实木弯曲家具生产中，主要采用蒸煮法软化木材。本文力求从高的自由体积理论出发分析木材软化机理，分析影响软化的因素，分析水和木材的软化作用。     

Über die Schwindungsanisotropie von Buchenholz

The shrinkage behaviour of beech wood was investigated with a drying microscope. Lamellae, transverse microsections, individual tissue zones, and tissue elements were examined with respect to the development of drying stress and the causes of possible tissue deformations. The study reports on the findings concerning the heterogeneous distribution of shrinkage capacities in transverse sections, the relationship between dimensional stabilization and the width and spacing of the rays. The passive role of vessels during shrinkage, the locally hindered shrinkage of fibre tissue, the zones of maximum tissue deformation during shrinkage and alternating atmospheric conditions, and the possibilities for the mechanical dimensional stabilization are described and discussed.     

应力释放对刨花板尺寸稳定性的影响

研究了热压过程中内应力的形成机理和板材内部应力状态,探讨了内应力释放对刨花板尺寸稳定性的影响,提出了减小内应力和提高尺寸稳定性的工艺措施。     

The effects of a two stage heat treatment process on the properties of particleboard

Steam pre-treatment can effectively improve the dimensional stability of panel products such as particleboard and fiberboard. At temperatures above 200–210 °C steam pre-treatment might result in a significant reduction of the bond strength of the panel product. The results of an effective two stage heat pre-treatment process, in which treatment temperatures below 200 °C are used, are given in this paper. The variations in process conditions which affect the particleboard properties are described in detail. A two- stage heat pre-treatment with temperatures below 200 °C appears to improve the dimensional stability of panel products. The process conditions used have an effect on thickness swelling and internal bond properties of the particleboard prepared, especially during the first process stage (hydrothermolysis). The best results were obtained with wood particles which were only thermolysed (without curing).     

Wood surface stabilization

The interaction between wood,Pinus sylvestris (60% RH), and polyethyleneglycol (PEG) of different molecular weights (PEG 200 and PEG 1500), pentaerythritol and glycerol, impregnated into wood, has been investigated using Scanning Electron Microscopy (SEM), dynamical mechanical techniques (DMTA), X-ray diffraction (WAXS) and macroscopic dimensional measurement. Reduced dimensional changes after impregnation, in environments with changing moisture content, show that the stabilization effect of glycerol impregnation is very good. The other chemicals used, especially pentaerythritol, were not as effective as glycerol. Cell wall measurements, using SEM, show that an increase in cell wall thickness gives a corresponding increase in stabilization effect. DMTA-measurements show that interaction between wood molecules and the chemicals used differs. In general, a higher degree of cell wall penetration of the chemicals show a better stabilization effect. PEG 200 was found to penetrate the cell wall much better than PEG 1500. WAXS-investigations show free crystalline pentaerythritol, PEG 1500, glycerol and PEG 200.     

Copper stabilization in ACQ-D treated wood: retention, temperature and species effects

The rates of stabilization or fixation of copper in ACQ-treated wood were compared for different post treatment conditioning temperatures (22°C and 50°C), solution concentrations (0.4–2.3%) and wood species. In some species, sapwood/heartwood differences were evaluated. The rate and extent of copper stabilization were estimated from changes in concentration of expressed solution at different times after treatment. The quality of the stabilization reaction was evaluated based on leaching performance of the wood after conditioning. Copper stabilized much faster at lower ACQ retentions and when conditioned at 50°C compared to high retentions and stabilization at 22°C. High retention treatments held without drying at 22°C could require five weeks or more for the copper to stabilize in the wood. Generally species effects were minor for the species evaluated, except for Douglas-fir in which copper reacted more quickly than in other species.     

Effect of thermal treatment on some properties of lime wood

Thermal treatment of lime wood was performed in a drying oven at two temperature levels (180 and 200 °C) and for four durations (1, 2, 3 and 4 h). Mass loss, color change, swelling and hygroscopicity were investigated. The dimensional stabilization reached up to 66.4 % and the hygroscopicity reduction up to 33 %, both maximum values being attained at 200 °C/4 h, associated with a mass loss of 9.3 %. The results will be realized in the manufacturing of solid wood panels made of heat-treated lime wood lamellas for outdoor uses.     

Kinetische Feuchteverformungsmessungen an chemisch modifiziertem Holz

Kinetic measurements of the swelling and shrinking of untreated and chemically-modified wood in the transverse plane were carried out in order to investigate the influence of various polarities and the volume of the introduced molecular group on the process of swelling and shrinking over time. To achieve this end, the hydroxyl groups of the wood were substituted with relatively small, but weakly polarized molecular groups, with significantly larger and strongly polarized molecular groups and with larger and weakly polarized molecular groups, and the degree of esterification was determined quantitativelly. It was found that the speed of swelling and shrinking is functionally dependent on the quality and kinetic characteristics of the function groups used. The decrease in the specific rate of shrinking and swelling, which is dependent on the sorptionally active molecular groups, follows the pattern: hydroxyl, acetyl, dibasic phthaloyl and monomethylphthaloyl groups. The relative, transverse deformation energy is used as a measure for the dimensional stabilization. This allows a quantitative evaluation of the above-mentioned modifications not only among themselves, but also as opposed to untreated wood. The mechanism of dimensional stabilization due to the modifications used is discussed with special reference to the dimensional stabilization due to the retardation effect. The influence of the function groups introduced into the wood on the kinetics of the shrinking and swelling anisotropy is studied, and a hyptothesis regarding the mechanism of anisotropy is made.     

三维横编间隔织物的编织工艺及其性能

为开发适合不同应用领域的曲面复合材料,采用新型三维曲面间隔结构,在电脑横机上用芳纶纱编织了带有双层罗纹连接中间层的横编间隔织物,探讨了编织步骤和编织工艺。在此基础上通过在间隔织物纬向的2个表层衬入芳纶增强纱,改进了织物的力学性能。通过调整编织程序,开发出不同曲率的间隔织物。在英斯特朗电子万能材料试验机上测试有增强纱和无增强纱织物的横、纵向拉伸性能,比较分析这2种织物的应力应变曲线。结果表明,在其他条件相同时,有增强纱的三维横编间隔织物横向、纵向拉伸应力增加明显,变形较少,织物尺寸稳定。