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 hydrolysatio n 98-99%, molecular weight 85000-146000) were selected for combination with PVA I (degree of hydrolysation 99%, molecular weight 17300) to prepare com posite films with different amounts of PVA I and film thickness. The permea bility coefficients of diclofenac sodium through these films were determine d 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 fi lms to diclofenac sodium, PVA VI-I films showed significantly higher permea bility than PVA V-I films. These results indicated that PVA I content in th e 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 sw elling properties was a more important factor. Film thickness also influenc ed the permeability coefficients of diclofenac sodium through the composite films; film permeability decreasing with increasing film thickness. The ad dition of PVA I raised the elastic moduli of PVA VI-I film but showed minim al 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.