Effect of Aluminium Nitrate Hydrate on the Crystalline, Thermal and Mechanical Properties of Poly(Vinyl Alcohol) Film

The effect of aluminium nitrate hydrate (Al(NO ₃ ) ₃ ·9H ₂ O) on the crystalline, thermal and mechanical properties of PVA was studied in this paper. The interaction between Al(NO ₃ ) ₃ ·9H ₂ O and PVA was investigated by Fourier transform infrared (FT-IR) spectroscopy. The influence of Al(NO ₃ ) ₃ ·9H ₂ O on the crystalline, thermal, and mechanical properties of PVA was studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile testing, respectively. The results indicated that Al(NO ₃ ) ₃ ·9H ₂ O could form interaction with the hydroxyl group on PVA chain. The XRD studies revealed that the crystallites of PVA were destroyed by Al(NO ₃ ) ₃ ·9H ₂ O. DSC studies showed that Al(NO ₃ ) ₃ ·9H ₂ O could increase the flexibility of PVA chains and decrease the T _g of PVA. Tensile testing showed that after the addition of Al(NO ₃ ) ₃ ·9H ₂ O the tensile strength of PVA film decreased and elongation at break increased. All these results show that Al(NO ₃ ) ₃ ·9H ₂ O has a high plasticizing efficiency for PVA. However, Al(NO ₃ ) ₃ ·9H ₂ O is a Lewis acid and the acidic property of Al(NO ₃ ) ₃ ·9H ₂ O would cause the significant decrease of the thermal stability of PVA.