Estimation of entry natural converging angles during capillary extrusion flow of carbon black filled NR/SBR compound

The entrance flow behavior during capillary extrusion flow of a carbon black filled natural rubber (NR)/styrene butadiene rubber (SBR) compound has been studied. Some viscoelastic parameters, such as entry pressure drop (ΔPen), non-Newtonian index and entry elastic stored energy (e) of the sample was measured at lower shear rates in the test temperature range from 100 to 110 °C. It was found that ΔPen and e increased non-linearly with an increase of shear rate while they decreased with a rise of test temperature. On the basis of previous work, an equation of entry natural convergent half-angle (α0) was proposed. Finally, α0 of the sample was estimated by means of this equation. The results showed that the predictions of α0 decreased non-linearly with increase of shear rate whereas it increased with a rise of test temperature.