Gas barrier and morphology characteristics of linear low-density polyethylene and two different polypropylene films

In this research, linear low-density polyethylene (PE-LLD), cast polypropylene (PPcast), and bioriented coextruded polypropylene (BOPP) were used as polymeric materials. Permeability, diffusivity, and solubility of N₂, O₂, and CO₂ through above polymers were obtained at different temperatures. The structure and thermal–mechanical features of the films were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The permeability, diffusivity, solubility, and their temperature dependency were studied by correlations with gas molecule properties. The highest permeation coefficients (>3.8 × 10⁻⁸ cm³ cm⁻¹ s⁻¹ bar⁻¹) are obtained for PPcast at 60 °C. Activation energy for permeation follows the sequence: N₂ > O₂ > CO₂ for PE-LLD and PPcast. On the other hand, the diffusion activation energy follows the order: O₂ > CO₂ > N₂ and N₂ > CO₂ > O₂ for PE-LLD and PPcast, respectively. In the case of BOPP, activation energy follows the sequence: O₂ > CO₂ > N₂; CO₂ > N₂ > O₂; and O₂ > CO₂ > N₂ for permeation, diffusion, and heat of sorption, respectively.