Influence of surface crystallinity on light barrier properties of polypropylene films.

FUENTES, ROCÍO A.; ALONSO, YANELA N.; CASTILLO, LUCIANA A.; BARBOSA, SILVIA E.

Buenos Aires

Congreso; 11th World Congress of Chemical Engineering (WCCE11); 2023

The development of light barrier films for food packaging has gained more interest in industry to protect products from deterioration and quality loss while it is exposed to light during transportation, storage and sales conditions [1]. To analyze the influence of surface crystallinity of polypropylene (PP) films on light barrier properties, PP films with different thicknesses prepared by compression molding with cooling under pressure were studied. In this sense, light barrier capacity of PP films with thicknesses ranging from 50 to 200 μm was determined from measurements of transmittance by UV-vis spectroscopy at 300 and 600 nm [2]. For the analysis of this optical property, transmittance values were normalized considering the film thickness. Crystalline phases and possible changes in surface and bulk crystallinity were analyzed by X-ray diffraction (XRD) and differential scanning calorimetric (DSC).In Figure 1, the normalized transmittance at 300 and 600 nm of PP films is presented as a function of thickness. These results showed a notable decrease in transmittance values with film thickness regardless of wavelength, which could be related to variations in surface crystallinity since bulk crystallinity was similar for all films. From XRD results, it was possible to observe an increment of surface crystallinity with the thickness, although all samples presented the same crystalline phases. This behavior could be associated with the differential cooling rate induced by film thickness, giving a useful tool to increase light barrier in thick films, changing their surface crystallinity.