Dissolution rate studies of compression-molded units made from hydroxypropyl cellulose films.

Hydroxypropyl cellulose films were prepared by compression molding of three different lots of hydroxypropyl cellulose powder at 149 degrees C, 188 degrees C, and 232 degrees C. Rectangular pieces were cut from these films and viscosity average molecular weight (Mv), degree of orientation, and rate of dissolution were measured. The viscosity average molecular weight (Mv) decreased with increasing processing temperature, while, as expected, the dissolution rate increased. Orientation in the thermoformed units was also evaluated. Correlation of these data with the Mv values suggests that orientation has some controlling influence on the dissolution rate. Because the samples possessing the least orientation were molded at the highest temperature, they also had the lowest Mv due to thermal degradation. Therefore, the effects of molecular weight were not fully separated from orientation effects with regard to control over the dissolution rate.