THE MECHANICAL AND MOISTURE PERMEABILITY PROPERTIES OF AQUEOUS-BASED HYDROXYPROPYL METHYLCELLULOSE COATING SYSTEMS PLASTICIZED WITH POLYETHYLENE-GLYCOL

The effects of polyethylene glycols (PEG 400, 1500 and 4000) used as plasticizer on the moisture permeability and mechanical properties of aqueous hydroxypropyl methylcellulose (HPMC) films were evaluated with free films. The free films were prepared by using a pneumatic spraying technique similar to that used in fluidized-bed coaters. There was a clear relationship between some physical film properties and the molecular weights and concentrations of the PEGs used as plasticizer. Over the range of concentrations tested, the moisture permeability of the films decreased slightly as compared to unplasticized control films with increasing molecular weight of the plasticizer. The mechanical strength of the films was shown to be more dependent on the concentration than on the molecular weight of the PEGs, while the ductility of the films was mainly dependent on the molecular weight of the PEG. The addition of PEG at a concentration of 10% resulted in relatively hard and strong films with a moderate elongation (ductility), especially when lower molecular weight plasticizers (PEG 400 or 1500) were used. As regards permeability to moisture and mechanical properties, the addition of PEG at a concentration in the range of 10-20% of the polymer weight seems to be beneficial for aqueous-based HPMC film coats.