STUDY OF THE MISCIBILITY AND THERMODYNAMICS OF CELLULOSE DIACETATE-POLY(VINYL PYRROLIDONE) BLENDS

The miscibility of blends of cellulose diacetate (CDA) and poly(vinyl pyrrolidone) (PVP) was extensively studied by means of differential th ermal analysis and dynamic mechanical thermal analysis, tensile test, measuring viscosity of diluted and concentrated solutions of blends in acetone-ethanol mixture and morphological observations. A single glas s transition temperature is observed, which is intermediate between th e glass transition temperatures associated with each component and dep ends on composition. A synergism in mechanical properties of blends wa s found. The absolute viscosity and the intrinsic viscosity of solutio ns of blends are much higher than the weight average values of solutio ns of CDA and PVP. Optically clear and thermodynamically stable films were formed in the composition range of CDA/PVP = 100/0 to 50/50w/w. F ourier transform infrared was used to investigate the nature of CDA-PV P interaction. Hydrogen bonds were formed between hydroxyl groups of C DA and carbonyl groups of PVP. Heats of solutions of CDA/PVP blends an d their mechanical mixtures were measured by using a calorimeter. Mixi ng enthalpy obtained with Hess's law approach was used to quantify int eraction parameters of this blending system. It was found that mixing enthalpies and interaction parameters were negative and composition de pendent. (C) 1997 Elsevier Science Ltd.