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Poor storage stability is a key problem restricting the rapid development and wide application of rubber-modified asphalt binder, and activation of rubber has shown good prospects to solve this problem. In this study, two activation methods, coating by polyamide 6 and grafting by acrylamide, were introduced to treat crumb rubber. Then the activated rubber was added to base asphalt binder to prepare modified asphalt binder. The chemical structure and morphology of rubber powder before and after activation and of asphalt binder before and after modification were characterized by Fourier transformation infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The conventional and rheological properties and storage stability were analyzed to reveal the influence of activation method on the performance of asphalt binder. The results showed that after being activated, the surface of the rubber is loose and rough. A chemical reaction did not occur during activation by polyamide but occurred during activation by acrylamide. The activation of the rubber effectively improved the high- and low-temperature performance, and the softening difference decreased by 79.8%. This is because the interaction between rubber and asphalt binder was enhanced through activation of rubber, and grafting activation had better effect due to the chemical reaction between the basic amide groups of acrylamide and acid groups of asphalt binder.

The nature of filler-polymer and filler-filler interactions in rubber composites under strain remains an open question in soft matter physics. These interactions are key to explaining the rich variety of complex behavior exhibited by particle-filled rubber products. In this paper we demonstrate a simultaneous dielectric/dynamic mechanical analysis technique (SDMS) which provides new insights into the structure-property relationships of filled rubbers. The complex permittivity of carbon black filled natural rubber has been characterized under a simultaneous tensile strain field (from 0.1% to 50%). The complex permittivity exhibits a dramatic nonlinear dependence on strain coupled with features which are analogous to mechanical strain softening and strain history, namely the "Payne" and "Mullins" effects. The sensitivity of the complex permittivity to such effects is several orders of magnitude greater than in corresponding, traditional mechanical tests. In addition, we demonstrate for the first time that it is possible to use both strain and electrical field frequency as "dipole filters" which can be used to selectively probe the dipoles present at the polymer-filler interface. [ABSTRACT FROM AUTHOR]