| 摘要: |
| 【目的】分析热压工艺参数对桑枝重组方材尺寸稳定性的影响，为桑枝重组方材的制备提供参考。【方法】以桑枝为原材料，以聚合异氰酸酯（P-MDI）为胶黏剂，以桑枝重组方材相对湿度在30%-65%-85%调湿过程中逐渐增加和逐渐减小时宽度、厚度方向的湿胀率及干缩率为考察指标，通过正交试验研究施胶量（6%，8%，10%）、密度（0.6，0.7，0.8 g/cm3）、热压时间（35，40，45 min）及热压温度（150，160，170 ℃）对制备的桑枝重组方材尺寸稳定性的影响。【结果】施胶量、密度、热压时间对桑枝重组方材宽度、厚度方向的湿胀率及干缩率的影响均随参数取值的增大而降低，热压温度对其的影响则随取值增大先降低后升高；影响桑枝重组方材湿胀率与干缩率的试验因素主次顺序为：密度>热压温度>施胶量>热压时间。在改变桑枝重组方材相对湿度的过程中，其厚度方向的湿胀率与干缩率均小于宽度方向，具有较强的方向性；同时，其宽度方向和厚度方向的干缩率明显大于其所对应的湿胀率，即存在吸湿滞后现象。【结论】密度对桑枝重组方材影响极显著，施胶量、热压时间和热压温度对其湿胀率与干缩率的影响均不显著。 |
| 关键词: 桑枝重组方材 热压工艺 尺寸稳定性 |
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| 基金项目:国家林业局林业公益性行业科研专项（201304511） |
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| Effect of hot-pressing on dimensional stability of mulberry branch reconstituted square lumber |
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ZHANG Jing,HUANG Zhonghui,XIAO Jianping,et al
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| Abstract: |
| 【Objective】This paper investigated the effects of hot-pressing technical parameters on dimensional stability of mulberry branch reconstituted square lumber to provide references for preparation of mulberry branch reconstituted square lumber.【Method】Taking mulberry branch as the raw material,P-MDI as the adhesive,and hygroscopic expansion and shrinkage expansion rates and vertical direction as evaluation standards,mulberry branch reconstituted square lumber was tested when relative humidity was increased and decreased gradually between 30%-65%-85%.Then,the influences of resin content (6%,8%,and 10%),density (0.6,0.7,and 0.8 g/cm3),hot-pressing time (35,40,and 45 min) and hot pressing temperature (150,160,and 170 ℃) on the dimensional stability of mulberry branch reconstituted square lumber were determined through orthogonal experimental.【Result】The influences of resin content,density,and hot-pressing time on hygroscopic expansion and shrinkage expansion rates of the anteroposterior and vertical direction of mulberry branch reconstituted square lumber decreased as the parameters increase,while the influence of hot-pressing temperature decreased first and then increased.The effects of the factors on shrinkage and hygroscopic expansion rates were in the order of density＞hot-pressing temperature＞resin content＞hot pressing time.In the process of changing relative humidity of mulberry branch reconstituted square lumber,the hygroscopic and shrinkage expansion rates of vertical direction were less than the anteroposterior direction with apparent directionality.Meanwhile,the shrinkage rates of anteroposterior and vertical direction were larger than hygroscopic expansion rate,which showed hygroscopic hysteresis phenomenon.【Conclusion】Density had the most significant effects on the dimensional stability of mulberry branch reconstituted square lumber,while the influences of resin content,hot pressing time and hot-pressing temperature were insignificant. |
| Key words: reconstituted square lumber of mulberry branch hot-pressing dimensional stability |
