大断面欧洲赤松的真空变定—高频干燥

Effect of Vacuum Drying Set and Radio-frequency/vacuum Drying on Wood Quality

对大断面欧洲赤松(Pinus sylvestris)进行真空变定/真空高频干燥及高温变定/高温干燥,对比研究木材表面变定对干燥材含水率分布、颜色变化及开裂的影响。结果表明:与高温变定/高温干燥相比,真空变定/真空高频干燥后木材含水率在长度及厚度方向分布均匀,但厚度方向上与高温干燥相反,呈现心层低、表层高的趋势。总处理时间基本一致,但高频真空干燥时间比高温干燥少9 h,干燥速度更快。高温干燥的L*、a*、b*及ΔE*的变化幅度分别是高频真空干燥的2.9、1.8、3.0及2.9倍,高频真空干燥后木材变色小,干燥后表面开裂宽度及长度比均小于高温干燥。干燥后木材含水率及开裂符合GB/T 6491—2012Ⅲ级室外建筑用材标准,对大断面木材做真空变定/真空高频干燥是一种更为优良的干燥方法。

Scots pine （ Pinus sylvestris）with large cross sections were dried using radiofrequency / vacuum and high temperatureafter vacuum setting and high temperature setting respectively. Compared with high temperature setting,the moisture content distribution along fiber and cross section after vacuum settingdrying was even,while that was low in the central location and high in the outer location at the cross section. The total treatment time was almost same,but radiofrequency / vacuum drying was faster as much as 9 h. The discoloration parameter of L＊,a＊,b＊and ΔE＊ were 2.9,1.8,3.0 and 2.9times to radiofrequency / vacuum. The surface crack situation was smaller than high temperature drying. The moisture content distribution and cracks met the national standard GB/ T6491-2012Ⅲ,and the vacuum setting with radiofrequency /vacuum drying was a practical drying method for large dimension timbers.