Effect of Electron Beam Irradiation on Gas-barrier Property of Biaxially Drawn Nylon/Montmorillonite Nanocomposite Films

Abstract

This study aimed to improve the properties, such as tensile strength and gas barrier properties, of nylon/montmorillonite nanocomposite films for them to be better suited for packaging applications. In this study, organic/inorganic nanocomposite films were fabricated by melt compounding with a twin-screw extruder using a polyamide (m-xylene diamine 6 nylon; MXD6) as the polymer matrix and organic nanoclay (montmorillonite; MMT) as a filler. An electron beam (EB) was irradiated onto the fabricated nanocomposite film and its effects on the film properties were examined. Biaxial drawing and annealing were conducted after EB irradiation to investigate the orientation of molecular chains and crystallization. Transmission electron microscopy revealed that the clay nanoparticles were finely dispersed in the polymer matrix. Furthermore, the EB irradiation-induced polymer crosslinking was verified by measuring the gel content in the films. Finally, the thermal properties of the film were verified by differential scanning colorimetry (DSC), and the light transmittance was examined using a UV-visible spectrophotometer. Application of the sequential process of EB irradiation, biaxial drawing, and annealing on the MXD6/MMT-5 wt% nanocomposite films increased their tensile strength by 56% and decreased thermal shrinkage by 26%, with a minimal loss of the optical transparency. Increasing both nanoclay contents and draw ratios resulted in improved oxygen-gas barrier properties. In particular, the gas barrier property of the MXD6/MMT-5 wt% film approximately doubled compared with that of the untreated specimen. The thermal analysis by DSC revealed that the crystallinity decreased because of the addition of MMT and the EB irradiation.