【作者】 张斌；

【导师】 王金满； 郭明辉；

【作者基本信息】 东北林业大学 ， 木材科学与技术， 2008， 博士

【摘要】 白桦作为天然速生阔叶树材,是我国北方重要的工业用材树种之一,以其材色白净、软硬适中、材质致密、纹理通直、构造均匀等优点,在家具制造、室内装饰和人造板用材中受到越来越多的重视。但白桦木材在自然干燥或人工干燥过程中易产生变色,特别是受真菌微生物侵染产生蓝变、褐变的条形纹理,对白桦优美的外观造成了破坏性的结果,一定程度上阻碍了白桦木材的加工利用。本文针对白桦木材存在的这一缺陷,从白桦木材干燥变色规律、变色机理以及生物变色等方面展开了系统研究,同时还对白桦变色的防治进行了探索性试验,以期为白桦干燥变色的防治及加工利用提供理论参考。通过在不同干燥温度、湿度条件下对白桦木材进行常规干燥变色过程的研究以及对其进行红外光谱和扫描电镜分析,初步掌握了白桦木材在常规干燥过程中的变色规律和变色的基本特点,白桦木材在常规干燥过程中产生的变色以黄变为主;并利用化学成分分析试验、变色模拟、颜色反应以及白桦浸提物成分分析等方法,结合红外光谱、X-射线衍射和扫描电镜等分析手段,揭示了白桦木材干燥过程中黄变材的变色机理。同时,对白桦木材的生物变色进行了比较系统的研究,主要包括白桦木材侵染菌的培养、分离、纯化以及初步鉴定,在白桦木材侵染菌作用下白桦木材颜色变化特点及木材化学成分变化,还研究了白桦木材侵染菌作用下试材重量变化,并通过红外光谱(FTIR)、X-射线衍射(XRD)和扫描电镜(SEM)等分析手段,揭示了白桦木材生物变色机理。本文还对白桦木材生物变色的化学防治进行分析和探索性试验。具体研究结果如下:1、白桦木材常规干燥变色的基本规律:①白桦木材干燥变色随着温度的升高总体呈现出加深的趋势,当温度超过80℃时,白桦木材干燥试样的色差值相对增加较快;②白桦木材干燥变色随着湿度的增大总体呈现出加深的趋势,当干燥温度低于80℃时,湿度不易超过70%,这样产生的变色相对较小;③通过径切面和弦切面变色规律分析,白桦木材在干燥过程中弦切面变色较径切面变色程度大,这应是由干燥过程中有色抽提物的迁移和挥发以及木质素等化学成分变化所引起的,基本与木材自身的结构与生长特点有关;④通过不同干燥方法的变色试验可知,仅对白桦木材变色影响的程度而言,微波干燥变色程度较小,其次是真空干燥,再次是气干(通风环境较好),常规干燥变色程度较大。2、白桦木材常规干燥过程中黄变材的变色机理:①通过对变色材的化学成分分析、浸提物颜色模拟试验、颜色反应试验以及红外光谱可知,浸提物质中存在苯(芳)环、酚羟基、醇羟基-OH,羰基-C=O,羧基-COOH以及酯基等发色基团与助色基团,这些基团在一定条件下形成发色体,使白桦木材的颜色发生变化,这也表明浸提物中含有多元酚类、有机酸或生物碱等物质;②通过X-射线衍射(XRD)分析可知,常规干燥和汽蒸干燥变色过程中木材结晶度基本没有发生改变,即木材本身性能没有受到破坏;③白桦木材在常规干燥过程中产生的变色主要以黄变为主,通过扫描电镜观察,其中没有菌丝和孢子生成,仅有溶出物存在。3、白桦木材生物变色的特点和变色机理:①分离出9种白桦木材侵染菌,并对其进行了初步的鉴定,其中有3种为接合菌亚门、有5种为半知菌亚门、还有一种为细菌类。而且利用白桦木材试样接菌试验,模拟白桦生物变色过程,并通过白桦木材试样化学成分分析、颜色反应等方法,初步揭示了9种白桦侵染菌对白桦木材生物变色的影响差异与变色特点;②通过对9种白桦木材侵染菌侵染白桦试材的重量分析试验,其中有2种侵染菌导致试材重量的减少,基本可以确定这两种菌应为木材腐朽菌;③通过对白桦侵染菌侵染白桦试材的化学成分析以及X-射线衍射(XRD)分析可知,纤维素结晶度发生了改变,木材主要成分受到一定的破坏;④通过对白桦侵染菌侵染白桦试材的扫描电镜分析可知,白桦试材的导管、导管腔、细胞壁、木射线与导管间的细胞壁充满了菌丝和孢子,并且菌丝穿过梯形穿孔板或管间纹孔以及木射线与管胞间纹孔蔓延生长;同时,利用饱和乙二酸水溶液及过氧化氢脱色处理白桦生物变色试材可知,白桦木材的蓝变、黑变和褐变等变色主要是由真菌引起的。4、在白桦木材生物变色的防治方面,主要开展了探索性试验。选择6种化学药剂进行抑菌圈试验,对白桦木材变色防治药剂进行筛选;并选择其中4种药剂用于白桦木材生物变色的室内防治试验,结果表明适当的化学试剂及其浓度能够抑制菌的生长,减轻白桦木材生物变色的程度。同时,由于不同药剂对侵染菌的作用效果不同,故进行化学药剂互配,这对于白桦木材生物变色的防治也是一种比较好的选择方法。更多还原

【Abstract】 Betula platyphylla Suk.is a quick growing hardwood and one of mainly industrial trees in northern China,it has many advantages such as white and clean surface,straight grain, moderate hardness,even structure,preferable quality and so on.So it is paid much attention in the furniture manufactures,interior decoration and the wood-based panel factories.However, it is easily discolored not only in natural drying but also during artificial drying,especially easily getting blue stain and brown stain when it is contaminated by some fungus,thus whose surface would be wholly destroyed and wide uses prevented in some extent.In this paper it carried on laboratorial study and analysis on the discoloration of Betula platyphylla Suk.wood,from the drying discipline,discoloration mechanism to the bacterial discoloration etc.as well as the exploratory survey on the treatments of the discoloration.It studied the discoloration law and basic features of Betula platyphylla Suk.during drying process with temperature and humidity variation,through FTIR and SEM,then it was found that the discoloration of Betula platyphylla Suk.is mainly yellow stain.Meanwhile,the discoloration mechanism was discovered with the investigation on the changing of chemical compositions,the loss of weight,the simulating of discoloration,tone reaction and analysis of extractives composition through FTIR,XRD and SEM.At the same time,it accomplished the cultivation,separation,purification,preliminary identification of fungi.Furthermore,the methods of preventing Betula platyphylla Suk.discoloration were analyzed and determined in the paper.The results are as follows:Firstly,the basic drying discoloration features of Betula platyphylla Suk.are:①The discoloration during drying process seems getting deeper with temperature growing,and when the temperature is above 80℃,the color difference increases much quickly.②The discoloration during drying process seems getting deeper with relative humidity growing,and when the temperature is under 80℃,the relative humidity should not beyond 70%;③The color difference at tangential cross of Betula platyphylla Suk.is larger than that at radial cross;④on the color changing of Betula platyphylla Suk.caused by different drying methods,the microwave drying is the least,oven-drying comes next,air-drying with better ventilation locates at the third,and conventional kiln-drying is the largest.Secondly,the mechanisms of yellow stain of Betula platyphylla Suk.during drying process include:①Through the chemical composition analysis,extractives color simulation experiment,color reaction and FTIR resolution,it was concluded that there exist chromophore and auxochrome such as phenyl,phenolic hydroxy,mellow hydroxyl,carbonyl as well as ester and ketone,and all these functional group come into being auxochrome groups under certain condition and make the wood discolored,which also testifies the existence of multivariate phenol,organic sour and biological soda in these extractives;②The crystallinity of Betula platyphylla Suk.wood measured by XRD has hardly any change in the course of conventional kiln drying.③When the primary yellow stain occurred at Betula platyphylla Suk.,it is observed through SEM that there is not any mycelium,in which only extractives exists.Thirdly,the characteristic and mechanism of discoloration of Betula platyphylla Suk.caused by fungi are:①There are nine kinds of imbue fungi distinguished,and through identification knows that three of which belongs to Zygomycotina subphylum,five classifies into Deuteromycotina subphylum,and one ranges to Bacteriophyta.From macro angel, preliminarily discover the discrepancy among the 9 imbue fungi contaminate the wood using the planting bacterium into the samples.②Through analyzing of the weight loss of Betula platyphylla Suk.wood that were planted nine kinds of imbue fungi,it found that the weight loss caused by two kinds of imbue fungi are much larger than the others as well as the raw,so these two kind of fungi can be wood decay fungi.③The crystallinity of Betula platyphylla Suk. gets some change,and the main chemical composition of wood is also destroyed at certain extent.④It is observed through SEM that there is mycelium exist in the vessel,cross-field and xylem ray,which can result in the blue stain and brown stain of Betula platyphylla Suk.Fourthly,six reagents were chosen to filtrate the chemical repellent of wood discoloration, and the results showed that proper reagent can restrain the growth of fungi and lighten the discoloration of Betula platyphylla Suk..更多还原