原位聚合酯化改性欧洲赤松的尺寸稳定性

  目的  针对木材在环境温湿度变化时易发生干缩或湿涨，导致木材尺寸不稳定的问题，提出以柠檬酸?山梨醇混合溶液作为改性剂，通过真空加压浸渍和高温固化改性木材。探究柠檬酸与山梨醇在木材内部原位聚合酯化对木材尺寸稳定性的影响，进而优化改性工艺。  方法  以欧洲赤松为原料，改性剂质量分数、固化温度、固化时间为考察因素，改性材的吸水抗胀率和改性剂的水溶流失率为响应值，采用响应面设计法，建立工艺与改性材性能之间的数学模型，通过方差分析各因素的显著性和交互作用，同时求解拟合方程获得柠檬酸?山梨醇原位聚合酯化改性欧洲赤松的优化工艺水平。并对改性材的尺寸稳定性、微观形貌和化学组分变化进行分析。  结果  固化温度对试样的吸水抗胀率影响极显著（P < 0.01），溶液质量分数和固化温度的交互作用对试样的吸水抗胀率影响显著（P < 0.05）；固化温度对改性剂的水溶流失率影响极显著（P < 0.01）。根据回归模型，结合可操作性和成本，提出最佳工艺条件—溶液质量分数30%、固化时间16 h、固化温度160 ℃。此条件下，改性材的吸水抗胀率为58.47%。电镜结果表明聚酯润胀了细胞壁，填充了部分细胞腔。红外光谱显示有酯键生成。  结论  利用柠檬酸?山梨醇原位聚合酯化改性木材，可大幅提升木材的防水性能和尺寸稳定性。这种改性方法对改善木材天然缺陷，实现木材高效利用具有一定的指导意义。 

Dimensional stability of Scots pine modified by in-situ polymerization esterification

ObjectiveTo address the problem of dimensional instability of wood due to dry shrinkage or wet rise when the ambient temperature and humidity change, we proposed to modify wood by vacuum pressure impregnation and high temperature curing using citric acid-sorbitol mixture solution as modifier. The effect of in-situ polymerization esterification of citric acid and sorbitol inside the wood on the dimensional stability of the wood was investigated to optimize the modification process.MethodUsing Scots pine as raw material, the solution mass fraction, curing temperature and curing time as the factors, water absorption anti-swelling efficiency of the modified wood and the leachability as the response values, the Box-Behnken response surface design method in Design-Expert software was adopted. The mathematical model between the process and the properties of modified wood was established. The optimum process level of citric acid-sorbitol in-situ polymerization esterification of Scots pine was obtained by means of variance analysis of the significance and interaction of each factor, and the fitting equation was solved. On this basis, the changes of dimensional stability, micro morphology and chemical composition of unmodified and modified materials were compared and analyzed. Result Curing temperature had an extremely significant effect on water absorption anti-swelling efficiency of the samples (P < 0.01), and the interaction between solution mass fraction and curing temperature had a significant effect on water absorption anti-swelling efficiency of the samples (P < 0.05). The effect of curing temperature on leachability was extremely significant (P < 0.01). According to the obtained response value, the secondary model of influencing factors and the actual situation, the process conditions were predicted and analyzed. The optimum process conditions were as follows: solution mass fraction was 30%, curing time was 16 h, curing temperature was 160 ℃, the water absorption anti-swelling efficiency value of the modified wood obtained was 58.47%. In addition, the mass percentage gain, bulking effect, dimensional stability, micro morphology and chemical composition changes of 13 groups of treated wood with different technological conditions were also compared. Conclusion It can be concluded that the modified reagent can easily enter the wood and undergo polymerization esterification in the wood cell wall. The modification of wood by in-situ polymerization esterification using citric acid-sorbitol can significantly improve the water repellency and dimensional stability of wood. This modification method is a guide to improve the natural defects of wood and achieve efficient use of wood.