Recycling Poly(ethylene-vinyl acetate) with Improved Properties through Dynamic Cross-Linking

Abstract

The low properties of recycled polymers associated with high cost of recycling hinder development of the thermoplastic recycling industry. Dynamic cross-linking of recycled thermoplastics with the formation of vitrimers enables superior mechanical properties, good reprocessability, and superior chemical and environmental resistance. Herein, a poly(ethylene-vinyl acetate) (EVA) vitrimer was formed by cross-linking with triethyl borate with the catalyst (bis-(acetylacetonato)dioxomolybdenum(VI)). The resultant EVA vitrimer shows enhanced thermal stability and mechanical properties with up to two times improvement in Young' modulus and storage modulus by comparison with the thermoplastic EVA. Moreover, 90% of Young's modulus was maintained in the EVA vitrimer after five times of recycling, whereas only 72% can be maintained for recycling the thermoplastic EVA. This dynamic cross-linked EVA also exhibits superior UV and solvent resistance, which helps extend the service time of the recycled material. This work introduces a facile and efficient method to recycle and reuse EVA with low property loss. It has the potential to enable the production of highperformance EVA from EVA waste for different applications.

Vitrimerization of Crosslinked Unsaturated Polyester Resins: A Mechanochemical Approach to Recycle and Reprocess Thermosets

“…The molecular weight between successive crosslinks, M e , can be obtained from G p ≅ ρRT/M e , where G p is the storage modulus of the rubbery plateau at temperature T and ρ is the polymer density. [ 40 , 41 , 42 ] A higher rubbery plateau modulus points out to higher crosslinking density. Thus, from the results we can conclude that the V‐3 sample has the highest crosslinking degree.…”

Polystyrene-Based Vitrimers: Inexpensive and Recyclable Thermosets

“…However, these benefits come at the cost of dramatically impeded reprocessability via conventional thermomechanical methods . To circumvent the static nature of thermosets without entirely compromising their stability, network structures containing dynamic linkages have been developed to permit cross-link exchange and macroscopic flow. , In particular, vitrimers have shown great promise in terms of material properties and reprocessability. , Thus far, most research has focused on the exploration of different cross-link exchange chemistries, − catalyst systems, − and network structures. − However, a critical hurdle for the application of vitrimers lies in the translation from the academic laboratory to industrially relevant materials and procedures. ,− For example, vitrimer materials have been developed using readily available, inexpensive monomers or postpolymerization modification from commercially available polymers. ,,− Our group recently prepared vitrimeric poly­(methyl methacrylate) mimetics that exhibited superior thermal and solvent stability while maintaining reprocessability through amine exchange of vinylogous urethane (VU) cross-links . Moreover, we reported that the phase separation present in vitrimers derived from block copolymers leads to enhanced resistance to macroscopic deformation as compared with networks prepared from statistical copolymers of identical compositions .…”

Enhancement of the Mechanical Properties of Poly(lactic acid)/Epoxidized Soybean Oil Blends by the Addition of 3-Aminophenylboronic Acid

“…The boric acid groups, which are bound to PLA or ESO, readily form boroxine, 20 , 23 while borate ester can be formed by the reaction between boric acid groups and the hydroxyl groups of PLA or those produced by the opening of the rings in epoxy groups. 22 The possible links by forming boroxine or borate ester in the blend can enhance the interactions between PLA and ESO, which helps to improve the compatibility between them. Moreover, these links allow for the extension of PLA chains to compensate for the decrease in their M n due to thermal degradation.…”