Study On The Discoloration Of The Drying Process And Biologic Inducement About Betula Platyphylla Suk.

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..