Rheological behavior and morphology of acrylonitrile-butadiene rubber/poly(ethylene-co-vinyl acetate) blends filled by various organoclay contents

The blends of acrylonitrile-butadiene rubber (NBR) and poly(ethylene-co-acetate) (EVA) with different mass ratios (20, 40 and 60 mass% NBR) and organoclay (OC) contents (1,3, 5 and 7 mass% OC) were prepared in an internal mixer. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed that for the nanocomposites containing 7 mass% OC, the majority of OC layers were exfoliated although some intercalated structures could also be observed. The scanning electron micrographs of the nanocomposites containing 40 mass % NBR showed that the rubber average domain size decreased significantly with the increase in the OC content in comparison with that of the corresponding unfilled blend. Atomic force microscopy (AFM) images indicated that the addition of OC improved the mixing efficiency of the two parent polymers by which the two-phase morphology could not be detected to any further extent. The rheological experiments showed that percolation was taken place when the OC content was about 3 mass%. Moreover, the elasticity of the materials containing 3 mass% OC and beyond was much higher than that of NBR and its value increased with the increase in the OC content. These nanocomposites also had a plateau region in the entire range of angular frequency studied.