预热温度对毛白杨压缩木材颜色及其回弹的影响

Effects of Preheating Temperatures on Color and Spring-back of Chinese White Poplar Compressed Solid Wood

为探究预热温度对压缩木材的色饱和度差(ΔC*)、色相差(ΔH*)、总体色差(ΔE*)、吸湿率、厚度变化和回弹率的影响,以毛白杨(Populus tomentosa)为研究对象,将其封端、浸水和放置后置于热压机上进行预热12 min,预热温度分别为90、120、150、180℃和210℃,预热完成后在相同温度下压缩5 mm。结果表明:随着预热温度的升高,ΔC*、ΔH*和ΔE*逐渐增大,温度>150℃,三者急剧增大,说明150℃是材色变化的一个关键温度点。随着预热温度的升高,压缩木材的吸湿率、厚度变化和回弹率逐渐减小,温度>150℃,三者急剧减小,说明150℃也是压缩木材尺寸稳定性变化的一个关键温度点。此外,ΔE*和回弹率呈线性负相关,ΔE*越大,其对应的回弹率越小。

In this study, effects of preheating temperatures on ΔC*,ΔH*,ΔE*, moisture absorption rate, thickness change and spring-back ratio were investigated. Poplar wood specimens after being coated with paraffin on the transverse sections, soaked in water and placed were preheated for 12 min at 90, 120, 150, 180°C or 210°C, respectively, and then they were compressed 5 mm at the same temperature. The results showed that increasing the preheating temperature resulted in an increase in ΔC*,ΔH* and ΔE* and they increased dramatically when preheating temperature was above 150°C. This indicated that 150°C was a key temperature point for color change. Meanwhile, increases in the preheating temperature led to a gradual lowering of moisture absorption rate, thickness change and spring-back ratio and they decreased dramatically when the preheating temperature was above 150°C. It could be concluded that 150°C was also a key temperature point for the spring-back. Furthermore, there was negative liner correlation between the ΔE* and spring-back ratio. The higher the ΔE*, the lower the spring-back ratio was.