Investigation of interfacial slip in immiscible polymer blends

In this study, we investigated an interfacial slip phenomenon occurring in immiscible polymer blends. We chose a binary polymer blend in which the interaction parameter, χ, between the component polymers is high, and thus the interface is thin and entanglement is weak. It was observed that the negative viscosity deviation (NVD) of the blends is large, which might be attributable to interfacial slippage between the interfaces. It was also observed that incorporation of a compatibilizer in the blends significantly reduced the NVD, via suppression of interfacial slip due to increased interfacial strength. We carried out a specially designed experiment to verify that interfacial slip is indeed responsible for the NVD. We prepared several blend samples having different phase sizes ranging from 50 ∼ 5 μm, and evaluated the shear stress vs. shear rate relationships of the samples using a capillary rheometer. We observed that the viscosities of the samples decreased as the phase sizes decreased, which is strong evidence of the occurrence of interfacial slip.