Effect of Formulation Conditions on Hypromellose Performance Properties in Films Used for Capsules and Tablet Coatings

This study investigated the effects of polymer dispersion and hydration conditions on hypromellose (HPMC) film properties, such as strength, oxygen permeability, water vapor transmission, clarity, and haze. The focus of the study was to build a better understanding of the impact that changes to HPMC dispersion and hydration conditions have on performance properties of the resulting films. This understanding could potentially lead to more flexible formulation guidelines for formulators. Films of HPMC 2906 (USP) were produced from aqueous solutions prepared using various formulation conditions. Results showed that tensile properties and oxygen permeability were not significantly affected by the variables used. The differences observed in water vapor transmission are unlikely to affect practical application of the material. However, the differences observed in clarity and haze at 50°C hydration temperature could affect the appearance of a capsule or coated tablet. Several methods were used to determine whether loss of optical properties was due to surface phenomena or bulk defects within a film. Results indicated that the cloudy appearance was primarily due to surface roughness. Based on this information, there is some flexibility in formulation conditions; however, hydration temperatures greater than 25°C are not recommended.