【作者】 陈勇平；

【导师】 王金林；

【作者基本信息】 中国林业科学研究院 ， 木基复合材料科学与工程， 2008， 博士

【摘要】 树脂浸渍单板重组材是以密度较低的木材特别是人工林木材为原料,经单板制备、调色、树脂浸渍、层积组坯、热压成型等加工制成的高性能高附加值木基复合材料。单板通过染色修饰和树脂浸渍增强,不仅能丰富单板的色彩,获得清晰悦目的花纹,而且可以改善和增强单板的性能,使重组材料的密度、耐磨性、耐水性、耐候性和尺寸稳定性等得到提高,从而为家具地板、室内装饰装修、体育器材和工艺品等制作提供优质材料。本项研究对于实现人工林木材的高效利用,缓解我国珍贵树种优质材的供需矛盾,满足市场对木质装饰材料的不断增长的需求,推动木材加工行业的技术进步等具有十分重要的意义。论文以杨树和桦木人工林木材单板为试材,采用常压与辊压法进行三聚氰胺甲醛树脂浸渍的全因子试验,并利用VB与Matlab建立单板树脂浸渍的调控系统;为赋予重组材一定的装饰性,开展木材单板染色计算机测配色和单板重组材料花纹仿真的计算机辅助设计的应用研究,研制材色和花纹仿真的重组装饰材料;利用高频热压设备,研究树脂浸渍单板层积板坯在高频电场中的温度场分布和变化规律;以单板树脂浸渍量、组坯结构和热压压力为变量,进行重组材的高频热压工艺和性能研究,采用方差和多重比较分析变量因子对重组材料性能的影响。论文的主要研究成果如下:1.研究提出了单板树脂浸渍方法,研制了辊压浸渍设备,选择浸渍用三聚氰胺甲醛树脂分别采用常压和辊压法进行单板树脂浸渍。常压浸渍是在常温常压条件利用树脂对单板的渗透作用进行定时浸泡;辊压浸渍是依赖单板离开压辊的瞬间真空作用把树脂液吸入单板,完成对单板的浸渍处理。常压浸渍中单板增重率随浸渍时间的延长而增加,但经历一定时间后浸渍量趋于稳定,如对于幅面85mm×55mm和360mm×180mm、厚度0.7mm~1.9mm的杨木和桦木单板,树脂浸渍3h后单板增重率趋于稳定;而辊压浸渍中单板增重率随辊筒间隙的减小(辊压压榨率的增加)呈增大趋势。幅面360mm×180mm厚度0.7mm~1.9mm的杨木单板常压浸渍单板干增重率最大为89.15%,辊压浸渍单板干增重率最大可达110.79%;而桦木单板常压浸渍单板干增重率最大为48.69%,辊压浸渍单板干增重率最大可达55.10%。杨木和桦木单板增重率的差异主要是由于木材密度不同,杨木密度低、孔隙度较大,所以杨木单板增重率大于桦木。2.树脂液进入单板的途径除纵向导管外,还包括横向通道。树脂浸渍单板的电镜照片表明,杨木单板内的树脂除渗入导管外,还存在于导管附近的木纤维中;桦木单板内的树脂主要存在于导管中。对于幅面360mm×180mm、厚度0.7mm~1.9mm的杨木和桦木单板,常压浸渍时间7h或辊筒间隙达到0.4mm时,树脂液可到达单板中心位置;两种浸渍方法相比,辊压法树脂液在单板中分布均匀,达到中心部位的树脂量也较多;两种树种相比,杨木单板中树脂液分布的位置广,这是由于同样条件下杨木单板浸渍树脂量远大于桦木单板。3.利用广义神经网络建立的树脂浸渍模型实现了常压浸渍和辊压浸渍中树种、单板纹理、单板厚度、树脂固体含量、浸渍时间或辊筒间隙等多方面信息与单板增重率之间的高精度映射,可根据要求进行树脂浸渍量的实时调控。模型相关系数均大于93%,平均相对误差均小于10.2%。4.在纺织印染用计算机测配色系统上开发完善的木材染色用计算机测配色方法与技术,在保证配色精度或配方经济的同时,快速计算出木材单板染色方案。与人工渐进法配色相比,具有准确、经济和快速自动配色的优点。利用建立的杨木和桦木基础数据库,进行黑酸枝、红酸枝、黑胡桃等珍贵树材仿真,分别修正0~2次后即能达到要求,所模仿的珍贵木材材色与天然木材相近,着色均匀,色差小。5.高频热压中杨木和桦木板坯内温度随时间变化曲线可用乘幂函数表示,若仅考虑其回归性能的优劣,该变化曲线用4次方以上的多项式函数表示也可达到很好的效果。对于板坯的温度场分布,在板材长宽(水平)方向,因边缘各点的含水率差异导致加热过程中温度的不一致,但在超过100℃后各点温度会逐渐趋于一个稳定值;厚度(垂直)方向上,高频电场中板坯的中心或两表层温度并非最高,最高温度出现在靠近正极板的部位,最低温度出现在紧贴负极板表层。6.当板坯厚度超过30mm时,利用高频介质加热进行板坯的胶合成型,可大大缩短热压时间,提高热压效率,同时保证各项物理力学性能。从热压效率来看,当含水率一定时,热压单位压力对高频加热板坯升温速率影响最大,以47mm厚板坯为例,压力从1.0MPa上升到2.5MPa时,所需热压时间下降显著;其次为单板的组坯厚度,同等条件下热压时间随着板坯厚度增加而增加;单板中的树脂浸渍量对热压时间影响不显著。对于材料的物理力学性能,由不同的树种、浸渍方式、常压浸渍时间(或辊压辊筒间隙)和热压单位压力条件下制备的重组材的物理力学性能研究可知,试验因子对材料的性能影响的顺序是单板树种>高频热压单位压力>单板增重率(常压浸渍时间或辊压辊筒间隙);在相同的单板增重率条件下,浸渍方式不同材料的物理力学性能也会有一定的差异。7.本研究的重组材可以根据产品用途对材料性能要求进行自由设计,即通过材料的结构设计、单板浸渍树脂量的调控、板坯高频热压单位压力等工艺条件的选择,控制材料的性能,满足不同用途产品的要求。在本研究中,通过对主要影响因素的试验参数的控制,获得不同性能的重组材料,其物理力学性能的范围是:密度0.44g/cm3~0.91g/cm3,静曲强度32.16MPa~112.19MPa ,弹性模量3.64GPa~9.483GPa,吸水厚度膨胀率4.97%~1.03% ,吸水率19.33%~7.88% ,剪切强度3.39MPa~12.27MPa ;硬度15.84MPa~57.88MPa。由此可知,本研究可根据产品用途确定材料性能,通过对工艺参数的控制,获得可适用于家具地板、装饰装修、体育器材及工艺品制作等不同用途的重组材料。更多还原

【Abstract】 The reconstituted lumber made of resin reinforced veneers selected low density wood species especially plantation as raw materials, was manufacutured from veneer preparation, dyeing, resin infusing, forming and hot-pressing to a new kind of wood-based reconstituted lumber. Dyeing induced imparting wood with fancy color and clear surface texture, thereby greatly enhancing the decorative effects of wood products in service; resin infusing could improve density, fracture strength, abrasive resistance, water-proof ability, weathering resistance, dimensional stability of the reconstituted lumber. This study will provide a new method for the high value-added utilization of plantation, solve the contradiction between supply and demand of expensive wood species, expanding the plantation timber utilization.In this paper, poplar (Populus×canadensis cv.‘Sacrou 79’) and birch (Betula platyphylla Suk.) were selected as the raw materials, melamine-formaldehyde resin(MF) was selected as adhesive,Thorough studies on resin impregnation techniques for wood veneers under atmospheric pressure and pressure-rolling process, reconstituted lumber was made by high-frequency hot-pressing process. An appropriate resin impregnation technique for wood veneers was put forward by Visual Basic (VB) and Matlab; Wood veneer-based computer color matching system was developed for color matching techniques and vein emulating; High-frequency hot pressing process was used to analyze the variation of temperature inside the mats for thick wood-based panels. In addition, variance analysis and multicomparison was used to analyze resin infusion, mat forming and pressure worked on properties of the reconstituted lumber.The main research results are summarized as follows:1. The pressure-rolling equipment was explored and prepared in this study. Roll pressure was found to facilitate resin impregnation into wood substance, which is faster and more convenient than the atmospheric pressure. In general, the weight percentage gain (WPG) of wood veneers was not found to increase throughout the impregnation process. For wood veneers 85mm×55mm and 360mm×180mm wide, 0.7mm-1.9mm in thickness, the WPG slowed down after 3 h of impregnation. The WPG of veneers showed an increasing tendency with the decrease of the roller gap. More specifically for the veneers of poplar, the maximum WPG of 89.15% was obtained for the process of atmospheric pressure impregnation, while the maximum WPG of 110.79% was obtained for the process of roll pressure based impregnation. For the veneers of birch, the maximum WPG of 48.89% was obtained for the process of atmospheric pressure impregnation, while the maximum WPG of 55.10% was obtained for the process of roll pressure based impregnation.2. During the process of impregnation, the resin entered wood veneers mainly along the longitudinal direction, and this also occurred along the transverse direction. The resins infused into poplar veneers were mainly distributed within the vessels, and also in the xylon adjacent to the vessels, resin in birch was almost in vessels. WPG of poplar was much more than birch. For wood veneers 360mm×180mm wide and 0.7mm-1.9mm in thickness,the resin could arrived in centric position after 7h of immersion or the roller gap was set to 0.4mm. resin was more even by rolling than immersion so that resin could reach the centric site.3. Generalized neural network (GRNN) was established to predict the content of resin impregnated into veneers measured by weight percentage gain (WPG). GNN models included the relationship in the predictors such as wood species, veneer gain angle, veneer thickness, solid content of resin, impregnation time of resin and roller gap, and the dependent variable WPG. Correlation coefficients was over 93% and mean relative errors was less than 10.2%.4. Base on the computer-aided color matching system for printing and dyeing in textile industry, a corresponding computer-aided color matching system for wood dyeing application was developed. The most economical dyeing solution for wood veneers could be calculated automatically and the quality of color matching could also be guaranteed. Compared with the commonly used man-made color matching, the computed-based color matching system was more efficient, economical and convenient. Based on the established database for poplar and birch, the developed color matching system was used to carry out imitation of precious wood species such as Dalbergia fusca Pierre, Dalbergin bariensis Pierre and Juglans. It was found that the imitated wood colors were comparable to those of natural precious wood with 0~2 times of uniformity, they had litle color distribution and small color differences.5. For the process of high-frequency hot pressing of the reconstituted lumber, power function was appropriated in describing the variation of temperatures inside the mats as a function of time. Besides, fourth order polynomial function also performed well in describing the relationship if only the regression performance of functions was considered. In length-width direction, the temperature may be different in heating process due to the moisture content. However, when the temperature surpass 100℃, temperature will gradually become stable. Along the direction of the thickness, the highest temperature was observed neither at the middle nor the surface layers of mats in high-frequency electric field, it occurred somewhere close to the positive plate, and the lowest temperature occurrrd near the negative plate.6. When thickness of mat was exceeded over 30 mm, high-frequency hot pressing could reduce press time considerably, and greatly improve the production efficiency. When the moisture content of mats was constant, the factor that influenced the temperature elevation most during high-frequency heating was hot-pressing pressure. When the pressure was elevated from 1.0 MPa to 2.5 MPa, the pressing time needed for mats of 47 mm thick reduced from 35 min to 7 min. In addition, thicker mats appeared to result in more hot-pressing time needed when the other conditions were kept constant. It was also found that the content of resin impregnated into wood veneers had no significant effect on hot-pressing time. The order of these factors on the physical and mechanical properties of the lumber was: wood speices>hot-pressing pressure>WPG>method of impregnation. Different immersion method had different influence on physical and mechanical properties.7. The reconstituted lumber achieved in this paper can be designed according to the requirement of different products by structure design, resin control and unit pressure and so on. Different properties of reconsititued lumber was achieved with the density from 0.44g/cm3 to 0.91 g/cm3, MOR was 32.16MPa~80.40 MPa, MOE was 3.64GPa~9.48MPa, TS was 4.97%~1.03%, water absorption rate was 19.33%~7.88%, shear strength was3.39MPa~12.27 MPa, and hardness was 15.84MPa~57.88MPa, respectively. Parameters control could change the properties of reconstituted lumber, it could satisfy requirements of flooring, decoration, gymnasium equipments and other handcrafts.更多还原