杨木单板条层积材工艺参数的研究

以杨木为原料，在试验室条件下，研究了杨木单板条宽度、厚度与施胶量三个工艺参数与产品性能之间的关系，得出了回归方程井进行了优化处理，认为较佳的工艺参数是：单板条宽度ｂ＝１０ｍｍ，单板条厚度ｄ＝１．５ｍｍ，施胶量Ｒ＝１３％。     

泡桐单板条层积材工艺研究

以泡桐单板为原料,通过正交试验,研究单板条宽度、施胶量、热压时间、热压温度对泡桐单板条层积材力学性能的影响。试验结果表明:单板条宽20 mm、施胶量13%、热压温度130℃、热压时间20 min为其最佳工艺参数。     

杨木单板的湿热处理对单板层积材性能的影响

杨木单板的湿热处理规律以及对杨木单板层积材性能影响的研究结果表明,单板湿热处理后产生了塑化,形成了一部分不可恢复的变形,密度平均增加了38.7%;对抗拉强度的影响不显著;对单板压缩率和膨胀率有着特别显著的影响,单板平均压缩了27.8%,经24h水浸泡,单板恢复膨胀仅18.7%.单板湿热处理后经过低压压制,可以得到与高压压制相同密度的板材,且板材的断面密度差异小,水平剪切强度提高了27.1%,静曲强度增加了17.8%,弹性模量没有显著变化,吸水厚度膨胀率降低了约10个百分点.     

玻璃纤维增强杨木单板层积材弯曲性能的初步研究

研究玻璃纤维对杨木单板层积材弯曲性能的增强效果.试验结果表明:玻璃纤维对杨木单板层积材的纵横向静曲强度(MOR)、弹性模量(MOE)的增强效果显著,特别是横向的MOR、MOE的增强幅度更大,横向的MOE、MOR值分别提高了79.6%、60.2%.     

结构用杨木单板层积材力学性能特征值的研究

根据美国ASTM D5456《结构复合木材产品评价规范》评价方法标准及美国工程木材协会PRL-501《单板层积材性能标准》,对国产杨木单板层积材力学性能进行了检测和评价分析。通过拟合优度检验,发现杨木单板层积材力学性能与对数正态分布拟合得较好。杨木单板层积材力学性能特征值的研究可为我国结构用单板层积材特征值确定方法提供参考。     

热压工艺对密实型杉木单板层积材力学性能的影响

以自制低分子量酚醛树脂为胶黏剂,采用热压工艺对杉木单板进行密实化试验,研究干燥温度、压缩率、热压温度和热压时间对密实型杉木单板层积材力学性能的影响.结果表明:压缩率对层积材力学性能影响最大,其次是干燥温度、热压温度和热压时间;随着压缩率和热压温度的提高,板材的MOE、MOR都有不同程度的提高;随着干燥温度的提升和热压时间的延长,板材的MOE、MOR都呈先增大后减小的趋势;综合考虑,确定密实型杉木单板层积材的最佳热压工艺为:干燥温度60℃、压缩率35％、热压温度145℃、热压时间1.0 min/mm,在此热压工艺条件下制得的板材,其MOE和MOR分别达到了GB/T 20241-2006《单板层积材》120E级和180E优级.     

阻燃杨木碎单板条层积材研究

主要利用碎单板压制阻燃杨木单板条层积材,研究了P-N阻燃剂与酚醛树脂胶相容性及合适的热压工艺。实验结果表明:当P-N阻燃剂pH值调至10~11,阻燃剂用量为15%时,阻燃剂与胶粘剂相容性较好,随着阻燃剂用量增大,试件氧指数不断增大,内结合强度逐渐降低。较优的热压工艺为热压温度190℃,热压时间90 s/mm。     

浸胶法杨木单板层积材的热压传热分析

采用热电偶法测量杨木单板层积材在热压过程中表层和芯层的温度的变化规律,讨论了施胶方式以及浸胶量和热压温度、压力对板坯在热压过程中传热的影响.结果表明:施胶量相当时,浸胶方式在快速升温阶段的升温速度较快;同时随着浸胶量的增加板坯传热速度增加,但浸胶量不影响板坯的总热压时间.     

玻璃纤维增强结构用单板层积材热压工艺研究

通过玻璃纤维增强速生杨木制备杨木单板层积材(LVL),可提高杨木的强度等级,使其达到结构集成材层板的使用要求。采用正交实验方法,研究温度、时间、压力、偶联剂浓度、涂胶量对杨木单板层积材弹性模量、静曲强度、剪切强度的影响,其中主要研究热压工艺对力学强度的影响,得出的最优工艺参数为:热压温度130℃、时间100s/mm、压力1.2MPa。     

密实型杨木强化单板层积材制造工艺及应用前景分析

介绍了杨木强化单板层积材的制造工艺。杨木强化单板层积材的压缩率约为15％～40％，其硬度、抗弯强度、耐水性、尺寸稳定性等指标远高于普通单板层积材，可作建筑用木梁、立柱、水泥模板、家具、门窗、地板、车厢板、集装箱板等多种材料。它是一种很好的结构用材，市场前景十分看好。     

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     

杨木定向木片层积材的制备工艺初探

以杨木碎单板条为原料制备定向木片层积材(OSL),研究了单板条长度、宽度、热压时间与板材密度,对杨木OSL性能的影响。结果表明:板材密度是影响OSL性能的最主要因素;采用优化工艺生产的杨木OSL,性能远超EN300-2006中OSB/4等级板材性能要求。     

工艺因子对杨木碎单板PSL材性变异性的影响

利用杨木碎单板制造PSL,考察板密度、板厚度、单板条长度以及铺装方式对PSL材性变异性的影响。研究表明,材性变异性均随板密度、板厚度的增大而减小,随单板条长度的增大而增大,铺装方式的影响中平行定向铺装时最小,定向抛洒铺装稍大,≤30°角铺装时最大。各项工艺因子对顺纹抗压强度变异性的影响均较小。对工艺因子影响下的力学强度进行可靠性分析,得出PSL安全系数为:MOE 2.4~5.149;MOR 3.229~8.401;顺纹抗压强度1.131~1.54。     

杨树新无性系苗期生长节律研究初报

1999年引进35杨、74杨、7号杨3个杨树无性系，对其生长节律进行了观测和分析，结果表明，3个杨树无性系在扬中地区都能正常完成年生育周期，对本地的土壤、气候均能适应，7，8，9月为生长高峰期。     

增强型杨木单板层积材力学性能分析

采用玻璃纤维布与碳纤维布复合材料及分步热压法增强杨木单板层积材,研究了玻璃纤维布与碳纤维布复合材料的铺设位置及分步热压法对杨木单板层积材力学性能的影响.结果表明:两种增强方式对杨木单板层积材静曲强度(MOR)和弹性模量(MOE)的增强效果均较明显;采用对称铺设相同的增强材料时,铺设位置靠近杨木单板层积材表层时对MOR和MOE等力学性能的增强效果较铺设在靠近芯层时的增强效果明显;采用分步热压法可以明显改善单板层积材水平剪切强度.     

落叶松刨切薄木用材的改性与蒸煮工艺的研究

通过研究,筛选出一种高效、无毒、无污染的落叶松木材处理剂,并采用正交试验法得出落叶松刨切薄木用材的最佳蒸煮工艺。据此,可以达到溶出树脂、缓解应力、软化木材并制得合格的落叶松刨切薄木的目的。     

Impact of precommercial thinning on tree growth,lumber recovery and lumber quality in Abies balsamea

Abstract

Precommercial thinning (PCT) is often used to improve stand growth and value. While PCT may accelerate tree growth and reduce mortality, it may also have a negative effect on product quality. This study examined the effect of moderate and heavy thinning on tree growth, lumber recovery and quality in a natural balsam fir [Abies balsamea (L.) Mill.] PCT trial 35 years after thinning. Compared with the control, the heavy thinning increased merchantable tree diameter, stem volume per tree and lumber volume recovery per tree by 41.1%, 100.9% and 92.7%, respectively, reduced the Select Structural grade (the best grade) recovery by 33.7%. Thinning did not affect the no. 2 and better grade yield. There was a 12.2% and 15.0% difference, respectively, in the lumber bending modulus of elasticity (MOE) and modulus of rupture (MOR) between the control and heavy thinning. Moderate thinning had little impact on the visual grade recovery, lumber bending MOE and MOR. Heavy thinning is recommended if the goal is to get sizeable sawlogs in the shortest time, whereas moderate thinning is preferable if the intention is to minimize the negative effects on lumber quality while retaining modest tree growth and lumber recovery. Overall, PCT of very dense young balsam fir stands appears to be an effective and viable silvicultural treatment.     

Development of structural composite products made from bamboo II: fundamental properties of laminated bamboo lumber

This experiment explored the technical feasibility of using bamboo zephyr mat with pre-hot-pressed treatment for the manufacture of laminated bamboo lumber (LBL), which is similar in construction to that of laminated veneer lumber (LVL). Six LBL boards (made from four-ply bamboo zephyr mats) with approximate dimensions of 2×42× 42cm were fabricated using resorcinol-based adhesive. The experimental design involved three combinations of layered structures (types I, II, and III) and two LBL loading positions (H-beam and V-beam) during the bending test. These materials were then compared to ordinary LVL. Results indicated that the bending properties (moduli of rupture and elasticity) of LBL were comparable to those of LVL, but there was no significant effect on the physical and mechanical properties among the three types of LBL beam. Interestingly, orienting the glue line to the vertical direction (V-beam) could maximize the ultimate strength of the LBL.Part of this research was presented at the 49th Annual Meeting of the Japan Wood Research Society, Tokyo. April 1999, and at the Pacific Timber Engineering Conference, Rotorua, New Zealand, March 1999     

Dimensional stabilization of compressed laminated veneer lumber by hot pressing in an airtight frame

Abstract

The purpose of this study was to evaluate the dimensional stability and strength properties of compressed laminated veneer lumber (LVL) produced using a closed hot pressing system. LVL specimens were produced with varying number of veneers using either diphenylmethane diisocyanate (MDI) or a water-soluble phenol formaldehyde (PF) resin at varying temperatures (160–200°C), pressures (0.5–3 MPa) and hot-pressing times (2–16 min). Results show that the heating process decreases the recovery of compressive deformation in the veneers when subjected to cyclic moisture and heat conditions. Thickness swelling was approximately 5% after a drying, wetting and boiling cyclic test for LVL using the MDI resin and hot pressed at 200°C for 8 min. Modulus of elasticity and rupture increased for samples produced in both an open press and the closed press with an increase in the number of veneers and density, as did the absorbed energy in impact bending.