Heat Treatment Impacts on Film Morphology in Biaxially Oriented Polypropylene Films

Polypropylene is a versatile polymer with a wide range of applications, including food packaging. Especially, biaxially oriented polypropylene (BOPP) films are commonly used in the food industry due to their high mechanical strength, transparency, and barrier properties. However, thermal processing, such as sterilization, pasteurization, and packaging, can cause morphological deformation in BOPP films, leading to defects such as folding and shrinkage. In this study, the morphological deformation of BOPP films during heat treatment is investigated Thermal treatment is applied to the film structures at temperatures starting from 30°C to 130°C and increasing by 10°C. The chemical structures of the thermally aged BOPP films were examined by FTIR spectrophotometer. Surface morphology and microstructures of these films were examined by detailed AFM and SEM analysis. The results showed that thermal treatment caused significant morphological deformation in BOPP films. The mechanical and morphological deformation was more marked at temperatures above 90°C. FTIR analysis of the PP films showed that the chemical structures of the thermally aged films were not significantly affected by thermal treatment. FTIR analysis of films heat-treated at 70°C revealed significant changes in C-C bonds within the polymer chain, indicating degradation. However, AFM analysis revealed that the surface morphology and microstructures of the heat-treated films were significantly altered. Depending on the heat treatment, the surface roughness of the polymeric films increased. The results of this study provide new insights into the morphological deformation of BOPP films during heat treatment.