西南桦木材变色的主要原因

为了有效地防止和消除西南桦木材的变色,该文通过显微切片观察化学成分和FTIR图谱分析,研究了西南桦木材的蓝变、黄变或黄褐变,探讨了变色的主要原因.研究结果表明:①蓝变材的各项抽出物含量都比正常材稍低,细胞腔内物质明显减少;黄变材的各项抽出物含量都比正常材高,pH值为6.64,由正常的酸性材变为碱性材.蓝变材与正常材的FTIR光谱图一致;黄变材的FTIR图谱的1 741 cm -1(CO,羰基和乙酰基伸缩振动)吸收峰几乎完全消失,木材组分发生变化.②蓝变主要由变色菌引起,因充满了薄壁细胞胞腔的蓝变菌菌丝体的颜色或其分泌的色素被木材吸收所致;黄变主要为活立木自然保护变色,黄变材的所有薄壁细胞、一部分导管及少量木纤维细胞均被黄色树胶状物质所充填,它与树木生长过程中的生理变化密切相关.

Main causes of Betula alnoides wood's discoloration

Alder Birch ( Betula alnoides ) is an important, fast growing commercial tree species in southwest China. Its wood has good properties, but it is often inclined to change color, especially blue stain or yellow stain, during the course of growth or after logging, which seriously degrades the products and causes great economic loss. Through the microscopic analysis of anatomy structure, chemical composition analysis and spectra of FTIR, the causes and types of the discoloration are discussed in this paper, which is important for further research in preventing and removing the discoloration. The results show that: ① The extractive contents in all items of blue stain wood are a little lower than those of normal wood; those of yellow stain wood are much higher. The pH value of the yellow stain wood has an essential change from 5 32 to 6 64. There is no significant difference between the FTIR spectra of blue stain and normal wood. In the FTIR spectra of yellow stain wood, the absorption peak at 1 741 cm -1 (CO vibrating) nearly disappears completely, which indicates that the wood composition has some changes. ②All the parenchyma cell lumens of blue stain wood are occupied by fungi hyphae or mycelia; while those of yellow stain wood, even some vessels and fiber cell lumens, are filled with gum like materials. Thus, the blue stain is mainly caused by stain fungi. The yellow discoloration is mainly resulted from the abnormal physiological reactions during the growing period of the trees.