Thermal-oxidative ageing of polyoxymethylene (POM) copolymer in the oven at 100°C for 1, 2, 3, 5, 7, 10, 14 and 21 days and the influence of early thermal-oxidative ageing on POM structure and properties were studied by means of wide-angle X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry and tensile test. Based on the results, we found that the early thermal-oxidative ageing of POM copolymer can be divided into three regions. The region I is the initial 3 days. In this region, some molecular chains rearranged, resulting in internal stress relaxation, increase of crystallinity degree and grain size due to the perfection of crystal structure; both extended chain crystal (ECC) and folded chain crystal (FCC) increased and ECC grew faster than FCC. The region II is from 3 days to 10 days, and in this region, chain scission took place in amorphous region and led to chemi-crystallization. The region III is after 10 days. In this region, the structure and performance of POM copolymer reached a stable situation at this stage. In this work, the difference between skin and core were also analysed.

研究了聚甲醛(POM)共聚物在100℃烘箱中热氧化老化1、2、3、5、7、10、14和21 d以及早期热氧化老化对POM结构和性能的影响。通过广角X射线衍射、傅里叶变换红外光谱、差示扫描量热法和拉伸试验。根据结果​​，我们发现POM共聚物的早期热氧化老化可分为三个区域。 I 区是最初的 3 天。在此区域，部分分子链重新排列，导致内应力松弛，晶体结构完善，结晶度增大，晶粒尺寸增大；伸长链晶体(ECC)和折叠链晶体(FCC)均增加，且ECC增长速度快于FCC。区域II为3天至10天，在该区域中，无定形区域发生断链并导致化学结晶。区域III是10天后。在这个区域，POM共聚物的结构和性能在这个阶段达到了稳定的情况。在这项工作中，还分析了表皮和核心之间的差异。