Montmorillonite clay and quaternary ammonium silane-reinforced pullulan/agar-based nanocomposites and their properties for packaging applications

Abstract

Synergistic combinations of pullulan, agar, montmorillonite (MMT) clay, and quaternary ammonium silane (QAS)-based (Pullulan/agar/MMT clay/QAS) active nanocomposites were prepared by a simple, cost-effective method. The Pullulan/agar/MMT clay/QAS nanocomposites were studied via Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction analyses. The concentration of MMT clay played a very important role in the properties of the nanocomposites. However, the transparency of the composite was not significantly affected by the addition of MMT clay. The ultraviolet (UV) transmittance of Pullulan/agar/MMT clay/QAS was in the range of 91.4–79.8 at 600 nm. The thermal and mechanical properties were significantly improved by the MMT clay. The tensile strength and elongation at break of the composites were in the range of 23.8–39.7 MPa and 37.2–26.9%, respectively. The long alkyl chain in QAS significantly improved the hydrophobic nature of the Pullulan/agar/MMT clay nanocomposites, impacting the contact angle (66.2–71.2°), water vapor permeability (3.17–2.20 × 10−9 g/m2 Pa·s), and swelling ratio (1837–836%). The combination of Pullulan/agar/MMT clay/QAS had a synergistic effect on the rheological properties. MMT clay and QAS significantly increased the viscosity, storage, and loss modulus of the hydrogel composites. With the addition of QAS, the Pullulan/agar/MMT clay nanocomposites showed good antimicrobial activity against gram-positive and gram-negative pathogens.