Evaluation of permeability and mechanical properties of composite polyvinyl alcohol films

Among six grades of polyvinyl alcohol (PVA), PVA V (degree of hydrolysation 99.45%, molecular weight 140000-150000) and PVA VT (degree of hydrolysation 98-99%, molecular weight 85000-146000) were selected for combination with PVA I (degree of hydrolysation 99%, molecular weight 17300) to prepare composite films with different amounts of PVA I and film thickness. The permeability coefficients of diclofenac sodium through these films were determined and the elastic moduli measured. The permeability coefficients increased with the! amount of PVA I in the PVA V-I films, Conversely, the presence of PVA I in the PVA VI-I films decreased the permeability of the composite films to diclofenac sodium, PVA VI-I films showed significantly higher permeability than PVA V-I films. These results indicated that PVA I content in the composite films was a critical factor, affecting the apparent solubility and/or swelling properties, and thereby permeability of the composite films, For PVA V-L films, the effect of PVA I on increasing solubility played a dominant role, but for PVA VI-I films, the effect of PVA I on decreasing swelling properties was a more important factor. Film thickness also influenced the permeability coefficients of diclofenac sodium through the composite films; film permeability decreasing with increasing film thickness. The addition of PVA I raised the elastic moduli of PVA VI-I film but showed minimal effect on PVA V-I films, Proper selection of PVA grades and weight ratio was the key element to successful preparation of PVA composite films with the desired characteristics.