BUBBLE INFLATION TECHNIQUE FOR MEASUREMENT OF VISCOELASTIC PROPERTIES IN EQUAL BIAXIAL EXTENSIONAL FLOW

A bubble inflation technique is presented which was used to measure biaxial extensional viscosity and elastic properties of a polyisobutylene at room temperature. A theoretical experimental procedure, based on certain idealizations, was developed for establishing bubble growth under constant stress. The accuracy and reliability of the measurements are tested, and sources of error, and possibilities for future work are discussed. Several constitutive equations are examined with respect to biaxial extensional flow. Predicted behavior patterns are compared with experimental results.