Crystalline structure and morphology of biaxially oriented polypropylene film under the coexistence of organic silica particles and its influence on the adsorption diffusion of polar solvent molecules

In this article, a silica/EVA/PP composite was prepared by melt-blending nanosilica with polypropylene, and a surface-modified BOPP film was prepared by using this as raw material. SEM studies have shown the special microscopic morphology of the surface and its cross section. X-ray diffraction (XRD) characterized and analysed crystallinity, molecular orientation, and grain size in the modified film. Furthermore, the presence of microholes in the modified film was verified by positron annihilation spectroscopy. The results show that compared with the unmodified films, the modified BOPP films have higher crystallinity and smaller grain size. Its dense surface structure and reticular fibre bundle structure make the diffusion coefficient and solubility of ethyl acetate small in the film. The mechanical properties, barrier properties, heat resistance, and ink adhesion of this film have been significantly improved. Modified film can be used as the food packaging film which has high performance and low residue.