Structural and morphological stability of polypropylene packaging films post high-intensity pulsed light treatment

Polypropylene is one of the main polymers used in flexible packaging, standing out in the food sector for its good mechanical strength, chemical and thermal stability. In parallel, non-thermal technologies have become established in the food and packaging industry because they enable greater microbiological safety with less compromise of food quality. Among these technologies, pulsed light (PL) emerges as a promising alternative for in-package applications, since it allows microbial inactivation directly in the packaged food, minimizing the risk of recontamination. Thus, the present work aimed to evaluate the influence of PL on mono-material films of polypropylene (PP) and biaxially oriented polypropylene (BOPP), seeking to understand the material’s stability after processing. For this purpose, samples were subjected to different PL conditions, varying the number of pulses applied, covering doses of 6.24, 12.48 and 18.72 J/cm². After film processing, the PP and BOPP samples were submitted to scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). Overall, SEM, DSC and FTIR analyses showed no differences between PL-treated samples and the control, indicating maintenance of the material’s surface and its thermal and chemical characteristics. On the other hand, XRD indicated a slight increase in film crystallinity, rising from 39% in the control sample to 45% in the PP sample treated with 6.24 J/cm² fluence and from 46% in the control to 48% in the BOPP sample treated with 18.72 J/cm² fluence, suggesting that PL can influence the crystalline domains of the polymers. These results suggest that, under the evaluated conditions, PL did not cause surface, chemical, or thermal alterations, maintaining material stability; however, it may promote induction of material crystallization.