聚氨酯老化机理与寿命预测研究进展

Research Progress on Aging Mechanism and Life Prediction of Polyurethane

分析了聚氨酯在自然环境、荷载、自然环境与荷载耦合作用下的老化机理,对比了Arrhenius模型、裂纹分析法和S-N曲线法三种寿命预测方法的适用条件。结果表明:热和氧会使聚氨酯分子链断裂并产生过氧自由基,水分会渗透到材料中引起助剂迁移,紫外线会分解聚氨酯分子,生成有色基团从而使聚氨酯颜色变深;荷载使分子链断裂后氧化,使聚氨酯萌生裂纹并逐步扩大,直至材料断裂;自然环境与荷载耦合作用下荷载引起的分子链滑移会增大氧气和水分的扩散速率,并且荷载会加速聚氨酯的热激活过程从而提高紫外线照射下分子链断裂速率;聚氨酯材料热氧老化时可以使用Arrhenius模型进行寿命预测;承受荷载时采用裂纹分析法和S-N曲线法更合理,受自然环境与荷载耦合作用时须使用多种理论叠加模型进行寿命预测。

The aging mechanism of polyurethane under natural environment,load,and the coupling of natural environment and load was analyzed.The applicable conditions of Arrhenius model,crack analysis and S-N curve method ware compared.The results show that heat and oxygen will break the polyurethane molecular chain and produce peroxy radicals,moisture will penetrate into the material to cause additives to migration,and ultraviolet light will break down the polyurethane molecules to form colored groups to darken the color of polyurethane.The load breaks the molecular chain and then the material oxidizes,causing cracks initiation and gradually expand in polyurethan until the material breaks.The slippage of the molecular chain caused by the coupling of natural environment and load increases the diffusion rate of oxygen and water,and the load accelerates the thermal activation process of polyurethane to increase the rate of molecular chain fracture under ultraviolet light.The thermal and oxygen aging of polyurethane material can be predicted by Arrhenius model.It is more reasonable to use crack analysis method and S-N curve method when material bears load,and the life prediction of polyurethane material must be carried out by a variety of theoretical superposition models when it subjects to the coupling of natural environment and load.