机构地区:[1]中国林业科学研究院木材工业研究所国家林业和草原局木材科学与技术重点实验室,北京100091
出 处:《林业科学》2024年第7期105-116,共12页Scientia Silvae Sinicae
基 金:国家自然科学基金面上项目“基于生长轮尺度的早材与晚材机械吸湿蠕变行为及其互作机制”(32071689)。
摘 要:[目的]实时、同步测量楸木早材和晚材的水分吸着-解吸等温线以及木纤维组织、木射线、导管尺寸的变化比率,揭示早材和晚材不同类型组织的尺寸变化规律及其相互作用机理。[方法]以楸木心材同一生长轮内的早材和晚材为研究对象,采用动态水分吸附分析仪联用视频白光显微镜,在水分吸着-解吸阶段[温度设置为(25.0±0.1)℃,相对湿度变化过程设置为0%→95%→0%,以相对湿度10%为梯度进行升湿、降湿],同步测量早材和晚材的水分吸着-解吸等温线以及木纤维组织、木射线、导管尺寸的变化比率;在平衡含水率恒定阶段,考察“尺寸变化行为”与“平衡含水率”之间是否存在滞后现象。[结果]1)在水分吸附全过程中,早材和晚材均表现出明显的吸湿滞后现象,绝对滞后值随相对湿度升高先增大后减小,相对湿度70%时达到最大值;与早材相比,晚材的绝对滞后值较小。2)早材和晚材木纤维组织、木射线尺寸的变化比率均随相对湿度升高而增大;导管弦向直径变化比率随相对湿度的变化模式与之相反,在相对湿度95%时,早材和晚材导管弦向直径的变化比率分别为0.945和0.918。3)随着木射线与导管之间直线长度(L)增加,木射线弦向尺寸的变化比率减小,L≥200μm后不再发生变化;轴向尺寸的变化比率未改变或改变很小,在相对湿度95%时,早材和晚材木射线弦向尺寸变化比率的最大值分别为1.051和1.038。(4)在水分吸附循环过程中,早材和晚材木纤维组织、木射线、导管尺寸的变化比率均表现出明显的湿胀滞后现象,湿胀滞后值随相对湿度升高先增大后减小,相对湿度70%时达到最大值。(5)在水分吸着-解吸过程中,早材和晚材组织“刚达到含水率平衡态”的尺寸变化比率与“保持含水率平衡态180 min”后的尺寸变化比率相比未发生明显变化,可被认为是相等的。[结论]木质素对绝对滞后[Objective]The adsorption-desorption isotherms and wood fiber tissue,wood ray and vessel dimension of change ratio of Catalpa bungei earlywood and latewood were real-timely and synchronously documented.This work aimed to reveal the pattern and interaction between the dimensional changes of different tissues of the earlywood and latewood.[Method]The earlywood and latewood of the same growth ring in the heartwood of Catalpa bungei were studied using a dynamic vapor sorption analyzer combined with a video Dino X Lite Digital Microscope.The measurements were taken at a constant temperature of(25±0.1)℃,starting at 0%relative humidity(RH)and increasing in increments of 10%RH up to 95%RH,and then decreasing back to 0%RH also in 10%RH decrements.The each RH process was divided into the water vapor sorption period and equilibrium moisture content(EMC)constant period.During the water vapor sorption period,wood fiber tissue,wood ray and vessel dimensional change ratio and the sorption isotherm were synchronously measured.During the EMC constant period,whether there was hysteresis between“dimensional change behavior”and“EMC”or not was investigated.[Result](1)Throughout the moisture sorption process,both earlywood and latewood existed a significant hygroscopic hysteresis.The absolute hysteresis increased and then decreased with the increasing RH,reaching a maximum at the 70%RH level.Compare with earlywood,the absolute hysteresis of latewood was smaller.(2)The change ratio of wood fiber tissue dimension and wood ray dimension for both earlywood and latewood increased with increasing RH,while the change ratio of tangential diameter follow the opposite pattern of change with RH.The change ratio in tangential of earlywood and latewood at 95%RH was 0.945 and 0.918,respectively.(3)As the linear length(L)between the wood ray and the vessel increased,the change ratio of tangential dimension of wood ray decreased,and ceased to change after L≥200μm,while the change ratio of longitudinal dimension of wood ray remained unch
分 类 号:S781.3[农业科学—木材科学与技术]
正在载入数据...
正在载入数据...
正在载入数据...
正在载入数据...
正在载入数据...
正在载入数据...
正在载入数据...