COMPARISON OF SPHERE-SIZE DISTRIBUTIONS OBTAINED FROM RHEOLOGY AND TRANSMISSION ELECTRON-MICROSCOPY IN PMMA PS BLENDS/

Often, blends of two immiscible polymers have a morphology with one co mponent building a matrix in which spherical inclusions of the other c omponent are embedded. The theological response of such blends contain s an elastic contribution which can be attributed to the form relaxati on of the inclusions. This process has a characteristic relaxation tim e which is proportional to the radius of the inclusions divided by the interfacial tension between the blends' components. Thus a distributi on of radii leads to a distribution of relaxation times. It is shown t hat theological data together with an emulsion model can be used to de termine the volume weighted sphere-size distribution up to a scaling d epending on the interfacial tension. The procedure is applied to data of four PMMA/PS blends and the results are compared with the correspon ding distributions obtained from transmission electron microscopy (TEM ). If the concentration of the spherical inclusions is small, both res ults are in excellent agreement. For larger concentrations, deviations between the results from theology and TEM are observed. (C) 1995 Soci ety of Rheology.