Effect of blending on the molecular weight distribution of polymers

The effect of blending polymers of different molecular weight on the Q value (Q = M̄w/M̄n) of the blend has been considered. A mathematical expression is derived, and its shows by a simple application to monodisperse systems that blending over a wide molecular weight range is necessary to give high Q values. These principles are then applied to the case of Ziegler and Phillips type high density polyethylenes having wide log‐normal molecular weight distributions. In this way it is shown that only blending over a very wide melt index range, e.g., 1000/1, can be expected to have a measurable effect on Q. A series of physical measurements on blended and homogenized Ziegler polyethylenes shows no significant differences between blends and directly produced polymers.