Effects of Amide-Based modifiers on surface activation and devulcanization of rubber

Abstract

This paper examines the mechanisms of interaction between two modifiers in asphalt binder: an amide-based bio-modifier, and natural rubber vulcanized by sulfur crosslinks. The amide-rich bio-modifier surface-activates the rubber, cleaving the disulfide bonds and leading to partial surface devulcanization. Computational modeling and laboratory experiments were used to evaluate the devulcanization mechanism and its effects. Results show that non-covalent interaction between the –NH2 site of the bio-modifier and the S–S crosslink of the rubber is stronger than with the C–S part of the rubber, which can potentially induce partial devulcanization. This phenomenon is reflected in the empirical results: a reduction in viscosity, due to devulcanization; and an increased resistance to fatigue, due to improved interaction between rubber and bitumen. This study provides an in-depth understanding of the surface devulcanization mechanism of rubber, in addition to insights into the complex devulcanization process happening inside a bio-modified mixture of rubber and asphalt binder. The results of this study help expand the knowledge of bio-modifiers and present a new approach for devulcanization.