Abstract
The pursuit of high volume and high value-added applications for lignin has been a long-term challenge. In this work, inspired by the energy sacrificial mechanism from biological materials, we developed high-performance lignin/carbon black (CB)/nitrile rubber (NBR) elastomers by constructing a dual-crosslinking network consisting of sulfur covalent bonds and dynamic coordination sacrificial bonds. Lignin was not only used for the substitution of half mass of CB in the NBR elastomer but also served as natural ligands for the Zn-based coordination bonds, providing a significant synergistic coordination enhancement effect. The mechanical performance of the elastomers can be easily manipulated by adjusting the proportion of non-permanent coordination bonds and permanent covalent bonds. Lignin/CB/NBR elastomers with a higher strength and modulus than CB-filled elastomers were obtained while maintaining excellent elasticity. The thermal stability and the high-temperature oil resistance of NBR elastomers were also improved by incorporation of lignin and metal coordination bonds. Overall, this work inspires a new solution for the design of high-performance lignin/rubber elastomers with a high lignin loading content.
Highlights
Increasing concerns over global warming and resource scarcity have driven a rising focus on the development of green materials from biorenewable alternatives
Inspired by the energy sacrificial mechanism commonly existing in biological materials, the coordination sacrificial bonds were introduced into the lignin/carbon black (CB)/nitrile rubber (NBR) elastomers through adding ZnCl2 during the compounding process
The Cl− anions still existed in the composite system but they did not participate in the formation of metal coordination bonds within lignin/CB/NBR
Summary
Increasing concerns over global warming and resource scarcity have driven a rising focus on the development of green materials from biorenewable alternatives. The sacrificial bonds can undergo reversible rupture and reconstruction before covalent bonds break and effectively dissipate mechanical energy under loading. They can be reversible dynamic non-covalent bonds formed by hydrogen bonds, ionic bonds and/or coordination bonds [2]. When the energy sacrificial bonds are applied in hydrogels, the strength and toughness can be substantially improved [3,4]. Costantino [5] reported that the strength and toughness of polyacrylate elastomers were greatly improved by building a multi-level crosslinked network containing energy sacrificial bonds. The strength and the fracture energy of VPR were increased by seven and five times, respectively.
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