Improved tensile strength of acrylonitrile-butadiene rubber/anhydrous copper sulfate composites prepared by coordination cross-linking.

Acrylonitrile-butadiene rubber (NBR)/anhydrous copper sulfate (CuSO4) composites were prepared by coordination cross-linking. CuSO4 particles of different sizes are obtained by ball milling in acetone. During heat pressing at 190 °C, a strong cross-linking reaction occurred, which resulted from coordination between cupric ions and nitrile groups. Results showed that the mean size of CuSO4 particles decreased from 7.1 to 0.4 μm after ball milling. Accordingly, the number of coordination cross-linking points increased remarkably, which resulted in an increase in the glass transition temperature and equilibrium torque of the composites. Two models were employed to discuss the cross-link density and demonstrated that both CuSO4 particles and cupric ions contributed to the improvement of cross-linking points. It was noteworthy that this composite exhibited high strength and toughness, with 73.5 MPa tensile strength and 423.7% elongation at break. Moreover, a unique stretching phenomenon, including the features of both rubber and plastic, was observed and explained in detail. [ABSTRACT FROM AUTHOR]