Polyvinyl alcohol/α-zirconium phosphate nanocomposite coatings via facile one-step coassembly

Polymer nanocomposites containing inorganic nanosheets have attracted high interest due to their improved stiffness and strength, enhanced barrier properties, and superior flame retardancy after properly incorporating nanosheets. α-Zirconium phosphate (Zr(HPO4)2) (ZrP) is a layered compound that can be well exfoliated into single-layer nanosheets by propylamine in an aqueous dispersion. A polyvinyl alcohol (PVA)/ZrP dispersion was prepared and coated on polylactic acid (PLA) films, followed with crosslinking by glutaraldehyde (GA). The morphological, optical, thermal, barrier, and mechanical properties of the PVA/ZrP nanocomposite coatings were investigated. The ZrP nanosheets were uniformly distributed and well oriented in the PVA matrix. The coated PLA films exhibited high clarity even when containing 20 wt % of ZrP nanosheets. The crosslinked coating layer containing 20 wt % of ZrP nanosheets (PVA/ZrP-20-C) had an oxygen permeability of 0.022 [10−16 cm3 (STP)cm/cm2•s•Pa] and water vapor permeability of 0.25 [10−11 g (STP)cm/cm2•s]. Compared with the neat PVA, when 20.0 wt % of ZrP nanosheets were well-aligned and properly incorporated, the Young's modulus and tensile strength of the resultant PLA nanocomposite were increased from 1.5 GPa and 29.5 MPa to 13.9 GPa and 98.3 MPa, respectively.