MOLECULAR-DYNAMICS IN A MISCIBLE POLYESTER BLEND

The dynamic mechanical and dielectric spectra of a miscible polyester and polycarbonate blend are investigated with emphasis on the latter t echnique. It was found that relaxation spectra for the blends from bot h techniques are broader than those of the constituent homopolymers. T his is ascribed to greater intermolecular coupling and concentration f luctuations within the blends. The composition at which the greatest c oupling occurs is dependent on the relaxation technique used and is sk ewed towards the component which shows the highest degree of intermole cular coupling. A number of parameters, such as relaxation time of the polymer molecules in the blend and relaxation strength, are compared as a function of reduced temperature (experimental temperature scaled by the glass transition temperature). Whereas blend behavior is genera lly intermediate between that of the homopolymers, it appears as thoug h mobility of compositions with low polyester content have a greater r elaxation time and possess a higher activation energy when compared to a simple, weighted average of the corresponding homopolymer values. ( C) 1996 John Wiley & Sons, Inc.