investigation of rheological behaviors of pp and pp-pe copolymer

The objective of this paper is to study the rheological behavior of polypropylene (pp) and polypropylene-polyethylene copolymer (pp-pe). for this purpose, the rheological behavior of pp and pp-pe such as relaxation spectrum, relaxation time, stress relaxation modulus, storage modulus, loss modulus and loss factor was investigated. in this study, the rheology of the melted samples was measured in the linear viscoelastic region using a parallel plate rheometer. finally, it was observed that the relaxation modulus decreases with increasing the time of experiment in which the slope depends on molecular weight as well as molecular structure. the decrease of stress relaxation modulus of pp and pp-pe with time causes to enhancement of viscous flow behavior at longer time.