Photo-oxidation degradation behavior of isotactic polypropylene (iPP) has been extensively investigated, however, there are still some ambiguous points, e.g., the origin of improved crystallinity at the early stage of photo-oxidation, the evolution of condensed state structure during the process of UV light irradiation, etc. In the present work, iPP film samples, unstabilized and stabilized with a specific reactive hindered amine light stabilizer (RHALS), were exposed to UV irradiation for accelerated aging tests. The microstructural evolution of the samples was systematically investigated by combination of Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). The results show that chemi-crystallization exists both in unstabilized and stabilized iPP, but the chemi-crystallization extent is much lower in the stabilized iPP. In addition to chemi-crystallization, the loss of amorphous region induced by “UV light etching” is another probable factor contributing to the increase of crystallinity at the early stage of photo-oxidation. AFM results provide direct evidence that with the progress of photo-oxidation, the degradation gradually propagates from amorphous region to crystalline region, thus inducing the destruction of lamellar structure. On the basis of above results, a comprehensive model is summarized for the structure evolution of iPP film during photo-oxidation and will be of meaningful reference to the degradation investigation of other semi-crystalline polymeric materials.

等规聚丙烯（iPP）的光氧化降解行为已得到广泛研究，但是，仍然存在一些歧义点，例如，光氧化早期结晶度提高的起源，过程中缩合态结构的演变在本工作中，将未用特定的反应性受阻胺光稳定剂（RHALS）稳定和稳定的iPP薄膜样品暴露于UV辐射下，以加速老化测试。通过傅里叶变换红外光谱（FTIR），凝胶渗透色谱（GPC），差示扫描量热法（DSC），广角X射线衍射（WAXD），小角X-射线相结合的方法系统地研究了样品的微观结构演变。射线散射（SAXS）和原子力显微镜（AFM）。结果表明，在未稳定化和稳定化的iPP中都存在化学结晶，但是在稳定化的iPP中，化学结晶程度要低得多。除化学晶化外，“紫外光蚀刻”引起的非晶区损失是导致光氧化初期结晶度增加的另一个可能因素。原子力显微镜的结果提供了直接的证据，表明随着光氧化的进行，降解逐渐从非晶区传播到结晶区，从而导致层状结构的破坏。基于以上结果，总结了iPP膜在光氧化过程中结构演变的综合模型，对其他半结晶高分子材料的降解研究具有重要的参考意义。