Catalyst-Free Ethylene Vinyl Acetate Copolymer (EVA) Vitrimer Based on Titanate Exchange through a One-Step, Green, and Scalable Reactive Blending Approach

Cross-linked polyolefins are widely utilized across various industries due to their outstanding mechanical, thermal, and electrical properties. Due to their permanent cross-linked structure, postconsumption cross-linked polyolefins are hard to reprocess and recycle, leading to severe environmental pollution and resource waste. Vitrimers with dynamic cross-linked topological network reconcile the reprocessability of thermoplastic polymers with the excellent performance of thermosetting polymers, thus attracting extensive attention from both academia and industry. Although fruitful achievements have been witnessed concerning polyolefin-based vitrimers, the green and scalable preparation of catalyst-free polyolefin-based vitrimers remains a huge challenge. To address this issue, we designed a catalyst-free ethylene vinyl acetate (EVA)-derived vitrimer with dynamic titanate (Ti–O–C) cross-linkages. Taking advantage of the transesterification between carboxylate in EVA and titanate, EVA vitrimers were directly generated by cross-linking industrial-grade EVA and tetrabutyl titanate (TT-01) via a one-step and scalable reactive blending approach. Torque analysis, gel fraction tests, and DMTA study confirmed the effective cross-linking of EVA, while the successful formation of Ti–O–C cross-linkages was confirmed by FTIR spectroscopy. EVA vitrimers with excellent and tunable thermo-mechanical properties could be readily obtained by simply adjusting the feed ratio, with tensile strength and Young’s modulus almost doubled and tripled compared to EVA. Notably, after three reprocessing cycles, the tensile strength, Young’s modulus, and elongation at break remained nearly unchanged, highlighting the material’s robust recyclability. In summary, this work reports the first dynamic titanate exchange-based vitrimers that features a straightforward synthetic process, low cost, and readily available raw materials, robust mechanical properties, and excellent reprocessability.