influence of molecular weight, molecular weight distribution, random and impact co-polymerization on the rheological behavior of polypropylene

The purpose of this article is to investigate the effect of molecular weight, molecular weight distribution, random and impact  co-polymerization  on the rheological behavior of polypropylene. to achieve this goal, we performed a frequency sweep test on 5 grades of polypropylenes with different characteristics that are produced in navidzarchimi petrochemical company. after fitting the data obtained from the test on power law model, ellis model and carreau equations, the following results were obtained. it can be seen that with the increase of molecular weight, τ1/2 and flow behavior index decrease, zero shear viscosity, infinite viscosity and relaxation time as well as consistency coefficient increase. in the board molecular weight distribution, flow behavior index and zero shear viscosity, relaxation time and infinite viscosity are  higher than those in the narrow molecular weight distribution. in the random co-polymer, compared to the impact one, the infinite viscosity, relaxation time, zero shear viscosity, consistency coefficient increases, and flow behavior index and τ1/2  decrease.