Melt viscosity of polymers: Effect of polydispersity

Abstract

AbstractThe author's theory for the melt viscosity of high polymers is extended to include the effect of molecular weight polydispersity. It is found that if one describes the viscosity by the relation η = (const.)Mt3.5, the molecular weight average appropriate for Mt lies between the weight and z average. For molecular weight distributions with Mw/Mn less than about two, Mt is best represented by Mw. Above that value, Mz is a better approximation. These latter statements are not precise because of the fact that Mt appears sensitive to the exact form of the distribution. Reasonable agreement with available experimental data is found.