A wide distribution will affect viscosity-average molecular weight. Like the mixing of materials with large molecular weight and low molecular weight, small molecular materials as additives increase the fluidity between macromolecular materials, similar to the mixing of different substances, which reduces the toughness, strength and melting point of materials. The overall performance is not as good as that of materials with narrow distribution. Domestic polymers are not as good as imported materials in this respect, which is related to the domestic chemical technology level.
meaning
In order to accurately describe the molecular weight of polymer samples, besides the statistical average of molecular weight (number average molecular weight, weight average molecular weight, Z average molecular weight, viscosity-average molecular weight), the molecular weight distribution of the samples should also be given. Molecular weight distribution curve, distribution width index and polydispersity coefficient can describe the polydispersity of polymer samples. The distribution width index is defined as the square average of the difference between each molecular weight and the average molecular weight. The polydispersity coefficient is the ratio of weight average molecular weight to number average molecular weight or the ratio of z average molecular weight to weight average molecular weight.