Characterization of Polymers by GPC-Lalls. II. Concentration Effect of Polydisperse Polymers in GPC

Abstract

Abstract The concentration effect in a GPC is studied on the following polydisperse polymers: HDPE, EVA, EPM, and EPDM. The GPC is equipped with a dual detector system consisting of a LALLS and a differential refractometer. A proportional relationship is widely observed between the degree of the concentration effect and the elution concentration, and classified in two groups according to the molecular weight: in the first where the molecular weight is larger than 100–200 thousand, the effect becomes more severe as the molecular weight increases; and in the second where the molecular weight is smaller, the effect is less apparent with the molecular weight. The branched molecule is more gently influenced than the linear one. Hypothetical equations are proposed for the molecular coil-size-reduction effect and the viscosity effect under the experimental conditions. In combination they would constitute most of the concentration effect, though the estimation of the latter effect would remain uncertain because of the optional character of the equation constant. It is indicated that the correction of the concentration effect is necessary to measure long chain branches exactly by GPC.