Overcoming the Processability–Property Trade-Off in Biobased Thermoplastic Vulcanizates via Reactive Plasticization

Developing biobased and high-performance thermoplastic vulcanizates (TPVs) represents a vital paradigm shift toward sustainable elastomer engineering and a circular economy, yet their industrial processing is severely constrained by the melt-fluidity bottleneck. Conventional approaches typically rely on physical plasticization, which inherently suffers from the thermodynamically uncontrolled migration and uncontrolled phase redistribution of volatile plasticizers, inevitably compromising mechanical integrity and environmental friendliness. Herein, a green grafting plasticization strategy is developed to construct biobased TPVs (BBTPVs) consisting of poly(lactic acid) (PLA) and biobased polyester rubber (BPR) via in situ dynamic vulcanization. Tributyl citrate (TBC) is covalently grafted onto the PLA-based polymer structure using poly(ethylene glycol) diglycidyl ether as a reactive bridging agent, rendering the viscoelasticity of the grafted PLA precisely tunable and extending the phase inversion window during dynamic vulcanization. This widened time window enables efficient shear-induced breakup of the rubber phase at relatively low crosslink densities, yielding a refined sea-island morphology with the rubber particle size reduced from 2.04 to 1.17 μm compared to the physical blend. Consequently, the BBTPV achieves a tensile strength of 15.9 MPa and an elongation at break of 439%, representing improvements of 42% and 43%, respectively. Moreover, covalent bonding effectively suppresses plasticizer migration under organic solvent exposure and high temperatures, ensuring long-term service stability. Segmental mobility analysis further elucidates the mechanisms underlying the enhanced extrusion processability and excellent recyclability. Overall, this work provides a viable pathway toward high-performance, sustainable TPVs that overcome the processability–mechanical property trade-off.