木塑复合材料蠕变特性及预测方法的研究进展

State-of-the-art of the creep characteristics of wood-plastic composite and its prediction methods

木塑复合材料(WPCs)已广泛应用于建筑外墙板、户外铺板、室内装饰、园林景观、汽车内饰等非承重结构材料领域,但由于线型或支链型热塑性聚合物固有的粘弹特性决定了WPCs在受到长期力载荷时易发生蠕变变形,严重影响其作为承重结构材使用。因此抗蠕变是木塑产业界面临的重大技术瓶颈,也是学术界关注的核心科学问题。为更好地了解并改善WPCs的蠕变现象,本文综述了WPCs蠕变行为的研究进展,讨论了原材料、结构和环境条件等因素对其抗蠕变性能的影响,并对WPCs抗蠕变的改进方法进行了总结和分析。WPCs长期蠕变行为测试是评价其耐久性和安全性的必要手段,但传统的长期蠕变测试方法耗时且成本高昂。通过蠕变与时间、温度和外界应力等因素存在的经验关系,可以实现蠕变的加速测试。最后讨论了玻耳兹曼叠加原理、时间-温度-应力叠加原理、分步等温度法和分步等应力法等加速测试方法在WPCs长期蠕变预测中的应用。

Wood-plastic composites(WPCs) have been widely utilized in exterior cladding, decking, interior decoration, landscape architecture and automobile interior decoration, etc. WPCs will undergo creep when it is subjected to long-term external forces, which restricts its popularization and application as load-bearing structural materials. This is due to the intrinsic viscoelastic properties of linear or branched macromolecular chains ascribed to their thermodynamic movement. Therefore, increasing the creep resistance of WPCs is an international technique and academic problem needed to be attacked in both industry and academia. Towards a better understanding of creep behavior of WPCs and to improve its creep resistance, this paper reviews the state-of-the-art of the creep characteristics of WPCs. The effects of raw materials, structure, and environmental conditions on the creep resistance of WPCs were discussed. The improving methods for creep resistance of WPCs were summarized and analyzed. Thelong-term creep test of WPCs is a necessary means to evaluate its durability and safety, but the traditional testing methods are time-consuming and costly. Accelerated testing of creep can be realized by the empirical relationship between creep with time, temperature and external stress. Finally, the applications of Boltzmann superposition principle, time-temperature-stress superposition principle, stepped iso-thermal method and stepped iso-stress method in long-term creep prediction on WPCs were discussed.