Five different PVA/PAA blend films were prepared via the solution
blending method with heat treatment, and their physical characteristics
(including barrier, thermal, mechanical and optical properties)
were investigated as a function of PAA ratio. The physical
properties of the PVA/PAA blend films were strongly dependent
upon the chemical structure and morphology of the films. The
blend films were formed by esterification reactions between the
hydroxyl groups in PVA and the carboxylic acid groups in PAA,
resulting in a crosslinked network and changed chemical structure.
With increasing PAA ratio, the crosslinking density was increased,
resulting in more compact packing of the molecules. The glass
transition temperatures of the PVA/PAA blend films increased from
77.1 ∘C for pure PVA to 101.7 ∘C for the PVA/PAA 20% blend film,whereas the degree of crystallinity was decreased as the PAA ratio increased. The OTR of pure PVA decreased from 5.91 to 1.59 mL m−1 day−1 with PAA addition, and the water-resistance
properties of the PVA/PAA blend films were markedly enhanced.
The incorporation of PAA into PVA imparted not only good thermal
stability and transparency but also enhanced the barrier and
water-resistance properties of the pure PVA, making the PVA/PAA
blend films potential candidates for packaging applications.