The modification mechanism and the effect of magnesium chloride on poly(vinyl alcohol) films

The modification mechanism and the effect of MgCl(2) on poly(vinyl alcohol) and the effect of water in the system were studied in this paper. The effect of MgCl(2) on different fully dried PVA was investigated by Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimeter, thermogravimetric analysis, water content test, dynamic thermomechanical analysis and tensile test, respectively. The results showed that MgCl(2) was an effective strengthening agent, which could crosslink with PVA and then effectively decrease the crystallinity of PVA. With the addition of MgCl(2), the strength and rigidity of PVA increased and the melting temperature decreased. The effect of MgCl(2) on thermal stability of PVA was related to the alcoholysis degree of PVA. The tensile strength of PVA films modified with MgCl(2) were all over 120 MPa. Moreover, the effect of MgCl(2) on the dynamic thermomechanical properties and tensile properties of PVA with various content of water was studied. Water could interact with MgCl(2) to destroy the crosslink between MgCl(2) and PVA. In the presence of water, PVA modified with MgCl(2) became soft, with lower tensile strength and higher elongation at break.