The influence of interfacial interactions on the morphology and thermal properties of binary polymer blends

In order to understand the influence of interfacial modification in polyamide/ionomer/ polypropylene ternary blends, the binary blends were investigated. In this study two multiphase blends have been chosen, PP/ionomer and PA/ionomer, where the ionomer was a copolymer of polyethylene and of a mixture of methacrylic acid, zinc methacrylate and isobutylacrylate. The PP/ionomer blend is a classic example of an incompatible system which displays a high degree of interfacial voiding in SEM fracture surfaces, a strong negative deviation from additivity in the viscosity/composition relationship and an important coalescence effect on increasing dispersed phase concentration. This blend demonstrated increased nucleation and crystallization rate, compared to pure polypropylene. The second blend, PA/ionomer, demonstrates a very fine multiphase structure evident only after microtoming/etching of the sample, strong additive behaviour in the viscosity/composition curve. Formation of an amide bond was identified by Fourier transform-infrared spectroscopy. This evidence supports the conclusion that much stronger interactions exist between the ionomer and the polyamide than between the ionomer and the polypropylene.