Strengthened adipic acid cross-linked epoxidized natural rubber by cellulose nanocrystals

The formation of covalently cross-linked 3D network makes it difficult to recycle conventional vulcanized rubbers. Introducing dynamic covalent bonds such as reversible ester bonds into the rubber network is a feasible method to solve this issue. However, the low mechanical properties of rubber with only reversible ester bonds make it unsuitable for most practical applications. This work reports a strengthened biobased epoxidized natural rubber/adipic acid/cellulose nanocrystal (ENR/AA/CNC) composite in which biobased AA covalently cross-links ENR to form a network with exchangeable β-hydroxyl ester bonds. This network is able to rearrange its topology at high temperatures, causing the ENR/AA/CNC composite to exhibit certain reprocessing capabilities. Meanwhile, the CNCs form a mass of hydrogen bonds between their hydroxyl groups and the hydrophilic groups of ENR chains, giving the ENR/AA/CNC composite an enhanced mechanical performance. Graphical abstract