Miscibility, thermal, and mechanical studies of hydroxypropyl methylcellulose/pullulan blends

Miscibility of blends of hydroxypropyl methylcellulose (HPMC) and Pullulan in common solvent water were studied by viscometry, ultrasonic, density, and refractometric methods at 30 and 40°C. Further the blend films of HPMC and Pullulan were prepared by solution casting method and characterized by Fourier transform IR spectroscopy (FTIR), scanning electron microscopy, tensile measurements, thermogravimetric, and differential scanning calorimetric (DSC) methods. Using the viscosity data, interaction parameters were computed and it suggests that the blend is miscible when the HPMC content is more than 50% in the blend. The change in temperature had no significant effect on the miscibility of HPMC/Pullulan blends. The semimiscibility is confirmed by ultrasonic velocity, density, and refractometric methods. The specific intermolecular interactions of hydrogen bonding type of the blends were investigated by DSC and FTIR. The miscible compositions of HPMC/Pullulan blend showed improved thermal and mechanical properties.