Effect of the Addition of ENR on Foam Properties of EVA/NR/Clay Nanocomposites

Abstract

Abstract Elastomeric foams based on 60/40 EVA/NR blend nanocomposite were prepared by melt mixing EVA, NR and clay (5 phr) in an internal mixer, and later foamed with azodicarbonamide through compression molding. Epoxidized natural rubber (ENR) with epoxide content of 25 mole% was used as a compatibilizer to improve interfacial adhesion between EVA and NR. The addition effect of ENR concentration on the blending and properties of EVA/NR blend nanocomposite foams was studied. XRD and TEM results showed that the clay in the EVA/NR blends was intercalated and locally existed in the NR phase as well as at the interface between EVA and NR. The EVA/NR blend nanocomposites showed dispersed NR domains in continuous EVA phase. The addition of ENR into EVA/NR blend nanocomposites reduced the size of the dispersed NR phase, indicating that the blend miscibility was improved. Mechanistic model was proposed for the miscibility improvement of a two-phase structure of EVA/NR blend nanocomposite in the presence of ENR and clay dispersion. However, the improved blend morphology did not significantly affect the cell structure of EVA/NR blend nanocomposites. The observation of cell structure of EVA/NR blend nanocomposites suggested that the increased addition of ENR caused a little increase in cell density, and had no influence on cell size. Furthermore, with increasing addition level of ENR in the blend nanocomposite foams, the foam density slowly decreased, whereas the specific tensile strength slightly increased. The elastomeric recovery of blend nanocomposite foams decreased with increasing ENR content. The thermal conductivity of EVA/NR blend nanocomposite foams also decreased with more addition of ENR, which had beneficial result in improving thermal insulation property.