Non destructive monitoring of polymer degradation in photovoltaic modules using compressive stress relaxation method

Research background and core methods: During long-term outdoor service of photovoltaic modules, polymer materials such as encapsulation film and backplate will age due to factors such as heat, ultraviolet radiation, and oxygen, which will affect the insulation performance and mechanical integrity of the modules. Traditional evaluation methods often rely on destructive sampling or offline testing, making it difficult to continuously track in-service components. A study published in Volume 163 of Polymer Testing proposes using compressive stress relaxation measurement as a non-destructive method to monitor the degradation process of polymers in photovoltaic modules, and discusses its significance for module reliability evaluation. The authors of the paper are Patrick Wessel, Ralph Gottschalg, and Anton Mordvinkin, and the research was published in October 2026.

Method characteristics and detection significance

Stress relaxation reflects the changes in the mobility of polymer segments and the state of cross-linked networks.

. When a material undergoes polymer aging, processes such as chain breakage, changes in crosslink density, or plasticizer migration can alter its relaxation behavior. Therefore, this indicator can serve as an indirect characterization of the degree of degradation. The value of this study lies in linking this mechanical response to component level reliability: the measurement process does not damage the component structure and can be repeated at different aging stages, thus forming a longitudinal comparison of the same object. For packaging materials, this means that the evaluation of weather stability can be extended from “comparison before and after aging” to “tracking the aging process”, providing finer temporal resolution for life prediction and failure analysis.

Significance for the polymer additive industry

From the perspective of formulation design, the promotion of this method will change the focus of stability system evaluation.

. The commonly usedantioxidant systemandHALS(hindered amine light stabilizer) for encapsulation film mainly act on the oxidation chain reaction and photo oxidation process, and their effects will ultimately be reflected in the rate of change of material mechanical relaxation behavior. If compressive stress relaxation can sensitively distinguish the degradation rate of different formulation systems, it is expected to become an auxiliary means for screening weather resistant and stable formulations. Similarly, the synergistic effect of the complex system of UVA (UV absorber) and HALS in long-term outdoor exposure can also be obtained through non-destructive testing that is closer to actual service conditions, without relying solely on destructive testing after accelerated aging.

Limitations and Observations

It should be pointed out that the source only provides information on the research topic and author, and does not disclose specific experimental data, testing temperature, sample structure, and quantitative relationship with degradation degree.

. Therefore, the sensitivity of this method to different packaging material systems, its correlation with other aging characterization indicators, and its ability to distinguish the failure modes of different types of stabilizers still need to be supported by the original data. For additive companies, attention can be paid to whether this testing approach will enter the component reliability evaluation standards, as well as its connection with the existing antioxidant system, HALS, UVA formula validation process.

Source: Polymer Testing, Volume 163, October 2026; Authors Patrick Wessel, Ralph Gottschalg, Anton Mordvinkin.

Information source:Non-destructive monitoring of polymer degradation in PV modules by compressive stress relaxation measurement and implications for the PV module reliability， Organized by Herun Chemical.