Stress development in aqueous gelatin coatings

Stress in aqueous gelatin coatings was measured during drying. A cantilever technique was used to determine an average in-plane stress in coatings containing different weight percents of gelatin and dried under various conditions (i.e. humidity, temperature, etc.). The rate at which stress develops and the final magnitude of that stress were found to be function of the drying temperature, carrier gas velocity, and relative humidity. Chilling before drying was found to change the stress development rate and magnitude as well. Stresses measured at room temperature ranged from 10 to 40 MPa. These findings were used to determine processing conditions which allow for defect-free coatings with minimal stress.