Abstract
•Cross-linked poly(vinyl alcohol)/boric acid (PVA/BA) hybrid films were prepared.•Their physical properties were dependent on the BA content and cross-linking.•With increasing BA content, the thermal stability and tensile strength was improved.•Oxygen barrier properties and water resistance was greatly enhanced by BA loading.
To enhance the thermal stability and barrier properties of pure poly(vinyl alcohol) (PVA), five different cross-linked poly(vinyl alcohol)/boric acid (PVA/BA) hybrid films were prepared via a solution blending method, and their properties including barrier properties, thermal stability, transparency, and mechanical properties were investigated as a function of the BA content. The physical properties of the PVA/BA hybrid films were strongly dependent upon the chemical structure and morphology of the films originating from the amount of BA and change in degree of cross-linking. With increasing BA content, the size and amount of PVA crystallites decreased, whereas the cross-linking density increased, resulting in more compact packing of the molecules and lower free volume in the amorphous regions. The glass transition temperature and thermal stability were highly enhanced with increasing BA content. The oxygen transmission rate (OTR) of pure PVA decreased from 5.96 to 0.15cc/m2 day with increasing BA content and were greatly suppressed by 22.8% for 1% BA, 7.7% for 3% BA, and 2.5% for 3% BA, respectively, relative to pure PVA film. With increasing BA content, their water-resistant pressure and tensile strength increased with BA loading. All the hybrid films showed good transparency. These properties of the cross-linked PVA/BA hybrid films make them potential candidates for versatile applications as coatings, films, and packaging materials.