Polyolefins are subject to chemical changes when they are brought in contact with the environment. In the presence of UV-radiation and oxygen, photo-oxidation causes chain scission and cross-linking in polyethylene and polypropylene. This review provides a detailed presentation of the reactions that take place and their effects on the properties of polymers. In this review, radical formation and Norrish reactions are discussed in depth, along with the formation of peroxides and carbonyl compounds. More than a dozen different types of carbonyl compounds can be observed by FTIR. While Norrish reactions are the main reason for chain scission and molecular weight reduction, the initial step of the photo-oxidation may be related to the formation of O₂-polymer charge transfer complexes. Photo-oxidation takes place mainly in the amorphous region of the polymer, and polymers with a high tertiary-carbon content are more affected than those with straight chains. Chain scission occurs only in the presence of oxygen, whereas cross-linking in the absence of oxygen results in gel formation. Weathering conditions include seasonal changes, and the day-and-night cycle has a strong impact on photo-oxidation. The chemical changes occurring during weathering influence crystallinity and the mechanical properties of polyolefins. Most of the fundamental work in this field was published more than 30 years ago. It is necessary for the results of these early studies to be verified by methodologies developed in recent years.

聚烯烃与环境接触时会发生化学变化。在存在紫外线辐射和氧气的情况下，光氧化会导致聚乙烯和聚丙烯中的断链和交联。这篇综述详细介绍了发生的反应及其对聚合物性能的影响。在这篇综述中，对自由基的形成和诺里什反应以及过氧化物和羰基化合物的形成进行了深入的讨论。FTIR可以观察到十几种不同类型的羰基化合物。尽管Norrish反应是断链和分子量降低的主要原因，但光氧化的初始步骤可能与O ₂的形成有关-聚合物电荷转移络合物。光氧化主要发生在聚合物的非晶区，并且叔碳含量高的聚合物比直链的聚合物受到的影响更大。断链仅在有氧的情况下发生，而在无氧的情况下交联导致形成凝胶。风化条件包括季节变化，并且昼夜循环对光氧化有很大影响。风化过程中发生的化学变化影响聚烯烃的结晶度和机械性能。该领域的大部分基础工作已于30年前出版。这些早期研究的结果必须通过近年来开发的方法来验证。