Rheological characterization and wall slip of polymethylvinylsiloxane and high density polyethylene

The rheological behavior and wall slip phenomena in the shear flow of a commercial polymethylvinylsiloxane (PMVS) and a high density polyethylene (HDPE) were studied by using a rotary rheometer with parallel plates fixtures. The damping function obtained from the stress relaxation experiment was compared with the prediction results of Doi-Edwards theory with the independent alignment approximation (IAA) and that of Marrucci et al model. Wall slip phenomena in the steady shear flow for PMVS and HDPE were studied by checking the gap dependence of the shear-stress and shear-rate relation. The results show that when strain grows, the discrepancy between the experiment and theory increases probably in that single reptation considered is not enough for polydisperse systems. As the strain applied in stress relaxation increases, more than one peak stress values are obtained, suggesting that strain localization or stratified strain may occur inside the samples. In the shear stress range from 100 to 5 000 Pa, anomalous slip behavior can be observed for PMVS, while no obvious slip for HDPE.