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利用扫描电镜(SEM)对户外暴晒3～36个月的纯聚甲醛(POM)表面及断口形态进行了研究,揭示了材料的老化过程。讨论了老化层厚度、裂纹宽度、裂纹深度以及断口形态与老化时间的关系。结果表明:POM的老化导致了材料内部结构由韧性转变成脆性而使机械性能大幅度下降。 1.表面形态随老化时间的变化。POM老化的特征是由于受热、氧、光的综合作用而引起的结构变化,其形态主要表现是:龟裂、变形、粉化,最后使制品丧失物理机械性能。图1是不同老化时间下的POM表面形貌图。可以看出:POM在老化过程中表面发生龟裂,生成裂纹。随着老化时间的增长的裂
The surface and fracture morphology of pure POM (POM) exposed outdoors for 3-36 months were studied by scanning electron microscope (SEM), revealing the aging process of the material. The relationship between the thickness of aging layer, crack width, crack depth, fracture morphology and aging time is discussed. The results show that the aging of POM leads to the transformation of the internal structure of the material from ductile to brittle, which leads to the significant decrease of mechanical properties. 1. Surface morphology changes with the aging time. POM aging is characterized by structural changes caused by the combined effect of heat, oxygen and light. The main features of POM aging include: cracking, deformation, pulverization, and finally loss of physical and mechanical properties of the product. Figure 1 is the POM surface topography at different aging times. It can be seen: POM surface cracks in the aging process, the formation of cracks. As the aging time increases the crack