Storage Induced Performance Evolution of Peptidase-Treated Natural Rubber Through Dynamic Imine Bonds

The enzymatic coagulation process has emerged as a promising natural rubber (NR) processing method because of its high efficiency and environmental friendliness. However, the structural evolution of enzyme-treated NR during storage and its consequent effects on the properties of NR remain unclear to date, which restricts the practical application of the enzymatic coagulation process for the processing of NR. In this work, peptidase-treated raw NR was subjected to accelerated storage conditions. It was observed that during the storage process, dynamic imine bonds (–C= N –) were formed through condensation reactions between the –NH 2 groups generated from peptidase-hydrolyzed proteins and the –CHO groups from the NR backbone. The formation of these dynamic imine bonds did not significantly deteriorate the processing characteristics or vulcanization performance of the peptidase-treated NR. Moreover, the tensile strength of vulcanized NR increased from 19.2 to 26.1 MPa, and its toughness increased from 30.5 to 41.3 J/cm 2 , demonstrating an obvious self-strengthening induced by storage. Mechanistic studies revealed that dynamic imine bonds not only dissipate energy efficiently but also promote strain-induced crystallization (SIC), thus endowing the resulting vulcanized NR with improved strength and toughness. This work presents a comprehensive study of the structure–performance relationships of peptidase-treated NR during storage.