We designed novel self-healing thermoplastic vulcanizates (TPVs), achieving excellent thermal/magnetic/light-triggered shape memory assisted self-healing behavior. Damage on polylactide (PLA)/epoxidized natural rubber (ENR)/Fe3O4 TPVs could be healed via three events synergistically: the shape memory effect of TPVs resulted in the physical contact of damaged surfaces; the desorption–absorption of ENR/Fe3O4-bound rubber promoted interdiffusion of ENR chains, leading to the self-healing of ENR phase; ENR was grafted onto PLA segments to assist PLA rearranging and entangling again to achieve the repair of TPVs. This self-healing TPV is reported for the first time and paves the way to design next-generation self-healing materials.
We prepared a biobased material, dynamically vulcanized polylactide (PLA)/natural rubber (NR) blend in which the cross-linked NR phase owned a continuous network-like dispersion. This finding breaks the traditional concept of a sea-island morphology formed after dynamic vulcanization of the blends. The scan electron microscopy and dissolution/swell experiments provided the direct proof of the continuous cross-linked NR phase. This new biobased PLA/NR blend material with the novel structure is reported for the first time in the field of dynamic vulcanization and shows promise for development for various functional applications.
In this work, nitrile rubber (NBR) with high strength and recycling ability was designed based on the interaction between metal ions and ligands. Herein, we first epoxidized the nitrile rubber latex through the peroxyformic acid method. Dopamine was then grafted onto the epoxidized nitrile rubber via the ring-opening reaction followed by the introduction of Fe3+, which formed Fe3+–catechol group coordination bonds and acted as dynamic cross-linking points to connect separate NBR molecules. The NBR exhibited valuable mechanical properties due to the formation of the Fe3+–catechol group coordination bonds. For example, the tensile strength of modified NBR with 2.5 phr Fe3+ reached 8.93 MPa, which was far higher than that of most reported noncovalent supramolecular rubbers. Meanwhile, the reversible association–dissociation behavior of the Fe3+–catechol group coordination bonds endows NBR with excellent recycling ability (about 90% performance retention rate), which is considerably distinguished from that of conventional vulcanized rubber. The design of the recyclable cross-linked NBR with considerable mechanical properties is significantly meaningful in resource savings and environmentally friendly performance.
Recently, we have reported a novel core‐shell dynamic vulcanization method to prepare poly(vinylidene fluoride) (PVDF)/fluororubber (FKM)/silicone rubber (SR) thermoplastic vulcanizates (TPVs) with cross‐linked rubber core‐shell particles. However, the shell thickness on the properties has not been studied in detail. Herein, these PVDF‐based TPVs different FKM‐shell thickness were prepared by changing FKM/SR ratios. The effect of FKM‐shell/SR‐core ratio on morphology, crystallization, and mechanical properties of the ternary TPVs was studied. The results showed that the FKM shell had more positive effect on interfacial‐induced crystallization behavior than the SR core due to its better compatibility with PVDF. When the FKM/SR ratio was <1, FKM was not enough to encapsulate SR completely, which resulted in the formation of imperfect core‐shell structure. However, when the FKM/SR ratio was >1, perfect core‐shell structure was formed. Therefore, the mechanical properties improved with increasing FKM content; especially, a remarkable improvement was observed when FKM/SR ratio was >1. This study could provide more information for the design of TPVs with core‐shell structure.
Stiffness and toughness are two mutually exclusive attributes of polymer materials that contribute to significant improvements in impact strength, usually accompanied by a reduction in tensile strength. In this study, ternary thermoplastic vulcanizates (TPVs) consisting of poly(lactic acid) (PLA), poly(methyl methacrylate)-grafted natural rubber (NR-PMMA), and natural rubber (NR) with balanced stiffness and toughness were successfully prepared via peroxide-induced dynamic vulcanization. With 10 wt% of NR and NR-PMMA, the PLA/NR-PMMA/NR ternary TPV displayed an enhanced yield stress of 41.7 MPa (only 38% loss compared to neat PLA) and a significantly higher impact strength of 91.30 kJ/m2 (nearly 32 times that of neat PLA). The in situ compatibilization between PLA and rubber phases was confirmed by Fourier transform infrared spectroscopy. Interfacial, rheological, and calorimetric measurements confirmed that the NR was encapsulated by NR-PMMA in the PLA phase. It was found that the flexibility of the "soft" NR core and outer "hard" NR-PMMA shell with excellent PLA/rubber interfacial adhesion are responsible for the super toughness and considerable tensile strength of the PLA/NR-PMMA/NR ternary TPVs.
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