Polypropylene films with high barrier performance via crystal morphology manipulation

In this work, a simple and cost-effective method is proposed to prepare iPP films with high barrier properties. By adding a very small amount of beta-nucleating agent, three types of beta-crystal morphologies, namely, beta-spherulites, beta-transcrystals and beta-flower-like agglomerates are sequentially obtained in iPP with the increasing processing temperature. Among beta-nucleated iPP films, the one with beta-flower-like agglomerates demonstrates the best water vapor and oxygen barrier performances, whose water permeability coefficient is decreased by 50.3% and oxygen permeability coefficient by 67.5%, compared to pure iPP films. Refined crystals, sufficient connection within the crystallites and lamellae parallel to the gas flow direction in iPP with beta-flower-like agglomerates may force the gas molecules to take longer and more tortuous pathway, thus resulting in excellent barrier properties. Our work provides a new idea to prepare iPP films with high barrier properties by simply manipulating their crystal morphology.