Formulation Studies of Polyolefin Elastomer Encapsulants with Adhesion Promoters: Impacts on Adhesion Strength and Crosslinking Behavior

Delamination remains a critical challenge for the long-term reliability of photovoltaic modules. While adhesion promoters are essential for mitigating this issue, their impact on properties of emerging polyolefin elastomers (POE) is barely investigated in the literature. This study examines the influence of adhesion-promoter concentration on the adhesion and crosslinking properties of a series of self-made POE films. The variation of the adhesion-promoter concentration and its homogeneity was verified by the Fourier-Transform Infrared Spectroscopy. The gel content and crosslinking enthalpy, obtained by the Soxhlet extraction and differential scanning calorimetry (DSC), respectively, were found to increase with the increasing adhesion-promoter content, suggesting that the adhesion promoter is involved in the encapsulant crosslinking 180° peel tests on glass substrates revealed a non-monotonic relationship between the adhesion strength and adhesion-promoter concentration, exhibiting an initial increase of the adhesion strength, followed by a plateau, and a subsequent decrease thereof at higher concentrations. This three-regime behavior and the aforementioned Soxhlet and DSC results suggest an intricate interplay of competing mechanisms associated with the adhesion promoter: (i) intended reaction with the glass surface and the encapsulant; (ii) aggregate formation and participation in the crosslinking. The probability of the two reactions seems to shift towards the aggregate formation upon the increase of the adhesion-promoter content. The optimal range of adhesion promoter concentration was found to be between 0.25% and 1%, where the adhesion strength plateaus, but the gel content continues to increase. These findings highlight the importance of carefully optimizing adhesion promoter concentration to balance interfacial bonding and bulk crosslinking, ultimately contributing to the development of high-performance, delamination-resistant POE-based encapsulants for enhanced PV module durability. This work lays the foundation for assessing the lifetime of polymeric materials used in PV modules.