温度对杨木粉末温压成形表面颜色的影响

Influences of temperature on surface color of poplar flour formed by warm compaction

采用CIE(1976)L*a*b*系统和傅里叶红外光谱技术(FTIR),研究温压成形过程中温度对木材颜色和表面化学成分的影响规律。结果表明,成形温度升高可导致试件表面颜色加深,明度值变化范围为37.5%~79.2%,红绿色品指数变化范围为53.8%~207.7%,黄蓝色品指数变化范围为22.4%~110.3%;成形温度在180~200℃时ΔE*相差1.1,在180℃之前温度对杨木粉末的影响较为显著;随着温度的升高,半纤维素和木质素开始软化,导致试件表面颜色加深;这2类物质的降解主要存在侧链上,半纤维素降解程度高于纤维素和木质素。

Influences of temperature on surface color and chemical composition of poplar flour formed by warm compaction were investigated by CIE(1976) L*a*b * system and fourier transform infrared spectroscopy(FTIR).The results show that the surface color darkens with the forming temperature increasing.Brightness value varies from 37.5% to 79.2%,red-green product index ranges from 53.8% to 207.7% and yellow-blue product index ranges from 22.4% to 110.3%.The difference of Δ E * is 1.1 when forming temperature is between 180 ℃ and 200 ℃.When temperature is below 180 ℃, its influence on poplar flour is more obvious.Softening of cellulose and lignin begins with the increasing temperature and results in the surface color of the specimen darkened.The degradation of cellulose and lignin happens mainly in the side chain.Degree of hemicellulose degradation in the specimen is stronger than that of cellulose and lignin.