【作者】 韦双颖；

【导师】 顾继友；

【作者基本信息】 东北林业大学 ， 生物材料工程， 2008， 博士

【摘要】 我国人造板产品主要用于家具制造和建筑装修领域,对其装饰性有着较高的要求,需要进行表面装饰。以速生树种木材为原料制造人造薄木已成为弥补天然珍贵树种资源匮乏、发展木质装饰材料的重要途径之一。在制造人造薄木胶接技术中,改变常规制造工艺,取消单板干燥阶段,用胶黏剂直接胶接高含水率单板,致使其湿状胶合成为人造薄木制造的关键技术之一。而制造人造薄木过程中,单板需要经过染色、固色阶段,使单板表面性质发生了改变,单板表面被大量染料分子、固色剂分子所覆盖,致使对胶接产生直接影响。与胶接高含水率素材单板相比,胶接高含水率染色、固色单板要受到染料基团、固色剂基团化学性质的影响,包括对胶接界面的影响、对表面张力的影响、对润湿性的影响、对胶接性能的影响等等,最终导致对胶接效果产生影响。本课题从胶黏剂入手,以单组分湿固化异氰酸酯胶黏剂胶接高含水率染色、固色单板为切入点,首先对木材的漂白、染色以及固色过程进行了大量的前期研究工作,包括漂白剂、染料以及固色剂的选择;漂白、染色和固色过程中工艺参数的遴选;采用扫描电镜分析和傅立叶变换红外光谱分析手段,研究酸性染料在木材染色过程中,染料在木材上的渗透与附着过程;考虑到单板的颜色稳定性是保证人造薄木最终产品质量的重要保障,因此对染色、固色单板颜色稳定性展开了深入研究。结果表明,在浴比为1:15时,pH=10条件下,1.5mm厚的桦木和杨木单板最佳漂白工艺各有不同;酸性染料在桦木中的渗透与吸附研究证明,只有很少部分的染料分子能够进入到单板芯层,染色过程中,酸性橙Ⅱ分子与桦木的结合过程是以物理吸附为主;在6种金属盐固色剂中,KAl（SO₄）₂固色效果最显著,固色后单板变色小;采用壳聚糖溶液对染色单板进行后处理,可以得到最佳固色效果,而且处理后单板几乎不变色;质量分数为1%的壳聚糖溶液能够使单板具有较好的耐水、耐光颜色稳定性。其次深入研究了单组分湿固化异氰酸酯胶黏剂在素材、染色木材和固色木材表面的润湿性能。主要研究了在较高含水率条件下,以桦木素材、染色木材和壳聚糖固色木材作为被胶接材料,采用单组分湿固化异氰酸酯胶黏剂,通过测定不同胶接界面接触角θ,求出扩散—渗透系数K,用接触角θ和扩散—渗透系数K联合表征不同胶接界面的润湿性能,并对三种不同界面的润湿性能进行了对比分析。结果表明,三种界面的接触角均随时间的延长而明显减小,并且含水率越高,初始接触角越小,平衡接触角越大;含水率相同时,接触角变化为桦木素材最小,固色桦木最大,染色桦木比固色桦木稍有降低;随着含水率的升高,桦木素材、染色桦木和固色桦木三种界面的扩散—渗透系数K值均明显下降,但K值变化有所不同。接下来,在润湿性能研究结果的基础上,对单组分湿固化异氰酸酯胶黏剂胶接高含水率染色、固色单板的胶接性能进行系统研究,测定单板含水率、涂胶量、加压时间等主要影响因素对胶接性能的影响,得出最佳胶接工艺,并展开理论分析,为后续制造人造薄木提供指导。结果表明,含水率从50%增大到90%的过程中,素材干、湿状剪切强度始终最高,明显大于染色和固色两种试件;涂胶量小于120g/m²时,随着涂胶量的增大,素材、染色和固色试件胶接强度均逐渐增大;当涂胶量超过120g/m²后,三种试件的胶接强度均有所降低;三种试件的强度在加压1.5h后都达到最大值,随着加压时间的进一步增加,干、湿强度变化不大。最后系统分析胶接人造薄木用高含水率木材的胶接体系老化性能,通过胶接接头及异氰酸酯胶膜老化前后物理、化学变化的研究,揭示胶接体系老化前后的变化对胶接耐久性产生的影响,探讨胶接体系老化机理。（1）对胶接接头进行重复煮沸—干燥加速老化试验,利用万能力学试验机对老化前后的胶接接头进行力学强度检测,对影响胶接接头力学强度的因素进行了系统分析。结果表明,胶接接头经过水煮-干燥循环加速老化处理,一周期后压缩剪切强度均急剧下降,此后经过第二、三、四老化周期试验中检测的压缩剪切强度稍有波动。（2）对异氰酸酯胶膜进行重复煮沸—干燥加速老化试验和紫外光—湿热人工加速老化试验,利用扫描电镜、傅立叶红外光谱（FTIR）、动态力学性能分析（DMA）、光电子能谱分析等手段对老化前后的异氰酸酯胶膜的微观结构和化学官能团等变化进行研究,系统分析异氰酸酯胶膜老化前后物理和化学的变化,探讨胶膜的老化机理。结果表明,胶膜经过水煮—干燥循环加速老化处理后用DMA仪器进行分析,损耗角正切tanδ几乎没有变化;储存模量E′随着温度的升高而逐渐下降,在150℃以后逐渐趋向平衡。胶膜的初始储存模量E′相差很大,表现为E′_三周期＞E′_四周期＞E′_五周期＞E′_六周期;损耗模量E″在玻璃化转变温度以前,大小顺序为E″_三周期＞E″_四周期＞E″_五周期＞E″_六周期,在达到玻璃化转变温度以后,E″迅速降低,直至趋向于0;胶膜经过紫外光-冷凝水循环处理以后,用傅立叶变换红外光谱分析胶膜老化前后官能团的变化情况,发现采用CaO作为消泡剂的胶膜老化后—N=C=O基团特征峰消失;表征氨基甲酸酯的特征吸收峰明显减弱。采用二甲基硅油作为消泡剂的胶膜老化后—N=C=O特征吸收峰消失;—OH峰明显加宽;通过扫描电子显微镜（SEM）照片可以看出:胶膜老化前均匀、细致,没有气孔。在紫外光—冷凝水循环处理以后,胶膜的表面形貌发生了很大变化,加入CaO粉末和二甲基硅油作为消泡剂时其消泡效果具有明显的差别,二甲基硅油显示出了更加明显的消泡作用。利用X射线光电子能谱仪对老化前后异氰酸酯胶膜的表面化学状态进行分析,其拟合结果与胶膜老化前后FTIR谱峰归属结论相一致。更多还原

【Abstract】 Wood-based panel products are mainly used in manufacturing furniture and decoration fields in China,which reqired them to be well decorated.Manufacturing artificial wood veneers by fast-growing wood species have become an important way to make up for the lack of resources and to develop wooden decorative materials.In the adhesion technology of manufacturing artificial wood veneers,veneers’ bonding quality at high moisture content was one of the key technologies because all of changing the conventional manufacturing process,cancelling veneer drying stage and bonding high moisture content veneers directly with the adhesive were requred.In the course of manufacturing artificial wood veneers,the veneers’surface property was changed by dying and fixing veneers.The veneers were covered by a lot of dyes and fixing agent that caused a direct impact on veneers’ adhesion.Compared to bonding higher moisture content raw veneers,bonding effect of dyed veneers and fixed veneers were impacted by chemical group nature of dyes and the fixing agent,including the impact of adhesive interface, wettability,bonding property and so on.One-component moisture-curing isocyanate adhesive was used in the paper for gluing wet veneers dyed and fixed.So the processes of bleaching,dyeing and fixing were studied preliminarily,including the choice of bleach,dyes and the fixing agent,the process parameters selection of bleaching,dyeing and fixing,research of the penetration and adhesion process of acidic dyes to wood using SEM and FTIR analysis tools and the deep research to guarantee the color stability of the artificial veneer.The results showed as follows:the best bleaching process are different for 1.5 mm thick birch and poplar;Only a small part of the dye molecules were penetrated into the core layer of the veneer and absorbed which was physical process mainly proved by the research;The fixing effect of KAl（SO₄）₂ are the most that made small change to the veneers in six kinds of metal salts fixing agent;The best fixation effect of veneers were got in the way of post-processing veneer with Chitosan solution and the fixed veneers were almost no change.Good water resistance and light resistance of the fixed veneers were achieved after treating with 1 percent chitosan solution.Wettability of one-component wet-curing isocyanate adhesive on the wet surface of raw wood,dyeing and fixing wood was researched respectively.And wettability was characterized by contact angleθand spreading-penetration parameter K.Wetting property of these three different adhesive interfaces was compared and analyzed.The results show that The contact angle of these three interface all reduced significantly with the extension of time,and the higher the moisture content is,the initial contact angle is smaller,the balance contact angle is greater.With the same moisture content,contact angle of raw birch veneer is the smallest, that of fixed birch veneer is the largest,dyed veneer’s contact angle is between them.With the increase of moisture content,spreading-penetration parameter K of interface for the raw birch, dyed veneer and fixed veneer were significantly decreased,but the K-value decline of them was different.On the basis of the findings of the wettability study,bonding properties glued dyed and fixed veneers with one-component wet-curing isocyanate adhesive was researched.The major impacts on the adhesive properties such as veneers’ moisture content,adhesive spreading volume and pressure time was measured.The best adhesive technology was achieved and the theories were analysed.All of these findings provide guidance to the following manufacture of artificial wood veneers.The results show that dry and wet-shear strength of raw birch specimen has always been the highest in the course of moisture content increasing from 50%to 90% which significantly higher than dyed and fixed specimens.Bonding strength of these three kinds of specimen all gradually increased when the coating is less than 120g/m²,but with the coating more than 120g/m²,these three bonding strength all declined.The intensity pressed 1.5h to three kinds of specimen reached the maximum.With a further increase in pressure time, dry and wet bonding strength have little change.The aging performance of bonding system manufacturing artificial veneer with high moisture content of wood was analyzed.Compared to bonding system change before and after ageing course,its impact on the durability of bonding system was revealed and bonding mechanism was discussed.（1） the bonding joints were repeated by boiled - dry accelerated aging test,then mechanical strength of these joints were measured using of mechanical testing machine.The factors impacted on mechanical strength were analyzed systematically.The results showed that after boiled - drying cycle accelerated aging treatment,compression shear strength of bonding joints showed a sharp decline in one aging cycle.Since the second,third and fourth aging cycle, compression shear strength detected a slight fluctuation.（2） The isocyanate film was treated by boiled - dry accelerated aging test and UV - hot and humid accelerated aging test which change of micro-structure and chemical functional groups was researched and analyzed by SEM, DMA,FTIR and ESCA to try to reveal the aging mechanism of film.The results showed that after the film boiled - drying cycle accelerated aging analyzed by DMA,loss angle tangent（tanδ） had almost no change;storage modulus E’ gradually dropped with temperature increasing and tend to balance at 150℃;The initial storage modulus E’ of film vary greatly that expressed as E′_{three cycles}＞E′_fourcycle＞E′_five-cycle＞E′_6-cycle;the order of Loss modulus E″was E′_{′three cycles}＞E″_four-cycle＞E″_{five cycle}＞E″_{six cycles} before the glass transition temperature,then E″rapidly reduce until tend to 0 after reached this temperature.After film dealt with cycling UV - condensate water,the functional group changes in the ageing film was analyzed by FTIR.The findings showed that -NCO groups characteristic peaks disappeared in the film used CaO as a defoaming agent and -N-CO-O groups characteristic peaks significantly weakened.-NCO groups characteristic peaks disappeared in the film used dimethyl silicone as a defoaming agent and -OH groups characteristic peaks widen markedly.The film was uniformity,meticulous,no porosity in the SEM photos before aging.After dealt with cycling UV - condensate water,the film’s surface has undergone great changes.The defoaming effect adding CaO powder and dimethyl silicone oil as a defoaming agent showed significant differences and dimethyl silicone shown a more pronounced role in the anti-foaming.Making use of XPS instrument to analyze the surface chemical state of the isocyanate film before and after aging,its fitting results were consistent with FTIR spectra attribution conclusions.更多还原