Study On The Induced Discoloration Of Buerger Maple During The Drying Process

Buerger Maple (L.formosana Hance) is a kind of fast-growing hard wood in south China, which is in possession of the beautiful grain, bright color and compact wood property and is a perfect material in wood industry. Therefore, its utilization was restricted because it is discolored and decayed easily. This paper analyzed the mechanism of the discoloring for the natural defect that easily discoloration of Buerger Maple. A new conception was introduced about wood induced discoloring. An ideal result about induced discoloration was achieved by the study on the mechanism and process of induced discoloration during the drying process. It would inaugurate a vast prospect and new research direction in the study of wood science and technology. The research result would be significant and benefit for wood study and processing technology.This paper analyzed the mechanism of discoloring of Buerger Maple (L.formosana Hance) by means of the detecting component of extractives, the infrared spectrum (IRS) and the scanning electron microscope (SEM). The induced discoloring condition and mechanism was obtained by means of the induced discoloring process, the infrared spectrum (IRS) and the scanning electron microscope (SEM) analysis under different drying conditions. The discoloring tendency was achieved according to the analysis of visual physical parameters during inducing discoloration of Buerger Maple. The considerably induced discolouring drying technology was gotten primarily by the process experiment of the induced drying discoloration of Buerger Maple. The result shows that it is feasible to induce Buerger Maple discoloration. The optimum induced discoloring effect was gained under the high temperature and humidity, especially under the steaming pretreatment in high temperature (96 C~99 C) . The variation of wood color tends to red and fuscous colors.The results and innovation in this paper are shown as following:1. The induced discoloring mechanism is posted for the first time: (1) the extractives contain polyphoenol, leuco-macy and tannin, and certain chemical reactions make the wood change color under definite condations; (2) the chromophoric and auxochromicgroups of phenol, phenol- hydroxy, hydroxy (-OH), carbonyl (-C=O), carboxyl (-COOH), ester and ketone groups are contained in the extractives and they combined with carbohydrates existing in lignin forming some chromogenes, and they absorb then visible lights with certain wavelengths to make the wood develop colors.2. A new conception about the induced discoloration in wood is launched, and it presents a new researching direction of wood science and technology in China. The induced discoloring mechanism of Buerger Maple during drying process is opened out: (1) the high temperature and the high humidity (98%~100%) , especially high temperature(96 C ~ 99 C ) steaming accelerates the dissolution, pervasion and oxidation of polyphenol, leuco-fancy pigment and tannin, making the wood be pink and red. (2) the hydroxy (-OH) is oxidized and shifted to the carbonyl (-C=O), carboxyl (-COOH), ester and ketone groups during the inducing under the conditions of high temperature, high humidity and the high temperature steaming, which result in the change of the absorbing peak of the visible lights and the deepening of the wood color.3. An ideal induced discoloration drying technology of Buerger Maple is achieved by the experiment of induced discoloration drying process. The results show that there is perfect inducing discoloration effect with the warm-up and the steaming pretreatment drying process in high temperature, leading to sightly and uniform red colors emergencmg on wood piece. The induced discoloring drying technology are: (1) the high temperature warm-up: the relative humidity is 98%~100% and the temperature is as higher as possible to achieved a perfect induced discoloration effect; (2) the high temperature steaming pretreatment: the steam temperature is 96 C~99 C. It can not only obtain the optimum induced discoloration result, but the wood drying p...