Miscibility and thermal studies of PVP/Pullulan blends

Miscibility characteristics of Poly (vinyl pyrrolidone) and Pullulan have been investigated by viscometry, ultrasonic velocity and density techniques at 30 and 50 ºC. Blend films of PVP/Pullulan were prepared by solution casting method and characterized by scanning electron microscopic (SEM) and differential scanning calorimetric (DSC) techniques. Using viscosity data, interaction parameters of Chee’s (μ), and Sun’s (α) were computed to determine their miscibility. The interaction parameter value obtained revealed that at lower temperature (30 ºC) miscibility was found only at 90/10 PVP/Pullulan blend composition and at 50 ºC miscibility of blend compositions increased up to 70/30. The results were then confirmed by ultrasonic velocity, density, SEM and DSC techniques. Miscibility in the above compositions may be due to the formation of intermolecular hydrogen bonding between the carbonyl group in PVP and hydroxyl group in Pullulan. Thermogravimetric analysis (TGA) of 90/10 blend of Poly (vinyl pyrrolidone)/Pullulan showed increase in thermal stability.