The effect of blend ratios on physico-mechanical properties and miscibility of cross-linked poly(vinyl alcohol)/urea blends

Abstract

The present study investigates the effect of blend ratios on the miscibility and physico-mechanical properties of polyvinyl alcohol (PVA)/urea (U) blends. PVA/U blends were synthesized in aqueous solution with different blend ratios 65/35, 50/50 and 35/65 respectively, using glacial acetic acid as crosslinking. The properties of PVA/U blends examined included FT-IR, 1H NMR, 13C NMR, TGA, DSC and scanning electron microscopy (SEM). The obtained results showed that the miscibility and physico-mechanical properties of PVA/U blends are strongly dependent on PVA ratio in the blends. FT-IR spectroscopy was used to check the hydrogen bonding interaction between PVA and U in the blends. The formation of hydrogen bond was through the lone pair attraction from nitrogen atoms of U towards protonated hydroxyl of PVA. These blends have a single glass transition indicating that these blends are able to form a miscible phase due to the formation of hydrogen bonds. The addition of glacial acetic acid as cross-linking improved the thermal analysis of the blend. The scanning electron microscopy of PVA/U showed crystals of varying sizes with flake shapes compared to the pure PVA.