Viscoelastic behavior of NBR/EVA polymer blends: Application of models

The viscoelastic properties of blends based on nitrile rubber (NBR) and ethylene-vinyl acetate copolymer (EVA), a thermoplastic elastomer, are investigated in terms of storage modulus and loss tangent for different compositions. These small-strain dynamic mechanical properties have been evaluated using a Rheovibron Viscoelastometer covering a wide temperature range. Attempts have been made to fit the experimental results with computations based on mean field theories developed by Kerner. Predictions based on the discrete particle model (which assumes one of the components of the blend to be the matrix and the other dispersed as inclusions) are found to be satisfactory in the case of 30/70 NBR/EVA blend but not 70/30 and 50/50 blends. The packed grain model (which assumes neither of the components to be the matrix but approximates a co-continuous structure of the two) predictions do not agree with the experimental data on 50/50 blend for which a co-continuous morphology was revealed by SEM observations.