Influence of crystallization on the crosslinking behavior of polyolefin elastomer and its mechanism

As a semi-crystalline polymer, the influence of crystallization on the crosslinking behavior of polyolefin elastomer (POE) remains unclear, which restricts the enhancement of the crosslinking capability of POE photovoltaic encapsulation films. In this study, we discovered that the crystallization of POE significantly affects its subsequent crosslinking behavior and elucidated the underlying mechanism. Firstly, by comparing the crosslinking behavior and the microstructure of fully crystallized POE and non-crystallized POE, it was found that non-crystallized POE exhibited more thorough crosslinking. This phenomenon indicates that the presence of crystals impedes the complete crosslinking of POE. Subsequently, the mechanism underlying the influence of crystallization on the crosslinking behavior of POE was proposed. The strong exclusion effect of crystallization leads to an uneven distribution of crosslinking agents within the POE matrix, thereby restricting the sufficient crosslinking of POE. In particular, the strong memory effect of POE crystallization results in a localized absence of crosslinking agents in the ethylene-rich regions after melting, further limiting the crosslinking of POE. Finally, we attempted to mitigate the non-uniformity of crosslinking agents’ distribution by regulating the crystal size of POE. Experimental results demonstrated that smaller crystal sizes facilitate more sufficient crosslinking of POE, which further confirms the proposed mechanism. The insights provided in this study could offer inspiration and theoretical guidance for designing the microstructure of POE to enhance the crosslinking ability of POE photovoltaic encapsulation films.