Upcycling Waste Polycarbonate to Poly(carbonate imine) Vitrimers with High Thermal Properties and Unprecedented Hydrolytic Stability

Abstract

The global market for polycarbonate (PC) increases steadily because of its heat resistance, toughness, and optical transparency. To achieve sustainability, the waste polycarbonate (WPC) should be recycled. This work reports a 100% atom-efficiency upcycling of WPC to a WPC-derived aldehyde (WPC-CHO). Then, poly(carbonate imine) vitrimers (PCIs) based on the WPC-CHO and two aromatic diamines were prepared. Generally, polyimines can cleave in mild acidic conditions such as 0.1 M HCl(aq) and seldom show good thermal and tensile properties. The PCIs in this work showed good thermal and tensile properties and an unprecedented resistance toward acid hydrolysis. They can survive even immersing in a 5 M H2SO4 THF/H2O solution for 6 months. This unusual resistance toward acid hydrolysis expands the application of PCIs in an acidic environment. Small pieces of PCIs can be compression-molded into a newly formed polymer film at 240 °C. This thermal reprocessability demonstrates the vitrimer characteristic of the PCIs. The PCIs can be degraded through simultaneous aminolysis of carbonate and transimination of imine by hexylamine (HA) in a catalyst-free mild condition. Based on the aminolysis and transimination, we degraded the cross-linking network in the PCI-based carbon fiber-reinforced polymer (CFRP) and recovered undamaged carbon fiber. This environmentally friendly work will attract the attention of researchers who are interested in sustainability and circularity.

From vanillin to biobased aromatic polymers

“…In terms of utilization of polycarbonate waste particles, Reddy et al also synthesized WPC-derived aldehydes (WPCCHO) from waste polycarbonate (WPC) and vanillin derivatives, which were then condensed with two aromatic diamines to produce polycarbonate imide vitrimers (PCIs). 116 Unexpectedly, PCIs exhibited excellent resistance to acid hydrolysis and remained stable for 6 months even when immersed in 5 M H 2 SO 4 THF/H 2 O solution (Fig. 5).…”

Recent Trends of Recycling and Upcycling of Polymers and Composites: A Comprehensive Review

“…In the same direction, Zhang et al [277] designed a seven-membered ring carbonate containing trans-cyclohexyl fused rings as monomer for the synthesis of PC, achieving a polymer that can be easily depolymerised to its monomer. Also, another approach for upcycling of polycarbonate waste is chemical conversion to vitrimers; Reddy et al [278] developed polycarbonate imine vitrimers from waste polycarbonate with high thermal performance and hydrolytic stability that can be utilized for CFRP manufacturing. Composites can be chemically recycled via aminolysis in a catalyst-free, mild-conditions environment, providing a sustainable alternative for PC wastes.…”

An effective approach for the preparation of epoxy vitrimers by in situ formation of dynamic and permanent linkages in a one-pot curing reaction

“…7 Using zinc acetylacetonate as a catalyst for transesterification, the crosslinked epoxy networks became adaptable by the catalyzed transesterification between ester and hydroxyl groups. Based on their unique and attractive properties, vitrimers have received much research attention and significant progress has been made in recent years, 8 including catalystfree systems, 9,10 biomass-based vitrimers, 11,12 vitrimers based on various dynamic covalent bonds, 13,14 integration of vitrimer features into conventional polymers, 15,16 and vitrimer-based organic-inorganic composites. 17,18 Conventional thermosetting resins, such as epoxy resins, are prepared by a step-growth polymerization employing multifunctional small molecular monomers at high reaction conversions.…”