Base-Mediated Depolymerization of Amine-Cured Epoxy Resins

DiPucchio, Rebecca C.; Stevenson, Katherine R.; Lahive, Ciaran W.; Michener, William E.; Beckham, Gregg T.

doi:10.1021/acssuschemeng.3c04181

Cited by 9 publications

(5 citation statements)

References 29 publications

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“…Nevertheless, if suitable and efficient separation techniques for acquiring both the epoxy resins and fibers of the more common composite materials can be identified, the base-mediated process developed by our group could prove to be a simple and broad chemical technology for BPA recovery from epoxy resins. Independently and at the same time, Beckham and co-workers published a base-induced epoxy deconstruction using potassium tert -butoxide …”

Section: Depolymerization Of Epoxy Polymersmentioning

confidence: 99%

“…Independently and at the same time, Beckham and co-workers published a base-induced epoxy deconstruction using potassium tert-butoxide. 108 ■ OUTLOOK FOR THE DEPOLYMERIZATION OF EPOXY POLYMERS Developing economically and ecologically viable technologies for recovering base chemicals together with fiber textiles from state-of-the-art epoxy composites on a large scale remains a herculean challenge. Nonetheless, these recent first reports on the depolymerization of epoxy resins show that polymer blocks can be extracted from thermoset epoxy resins.…”

Section: ■ Depolymerization Of Epoxy Polymersmentioning

confidence: 99%

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Perspective on the Development of Monomer Recovery Technologies from Plastics Designed to Last

Kristensen,

Ahrens,

Donslund

et al. 2024

ACS Org. Inorg. Au

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In order to prevent the current unsustainable waste handling of the enormous volumes of end-of-use organic polymer material sent to landfilling or incineration, extensive research efforts have been devoted toward the development of appropriate solutions for the recycling of commercial thermoset polymers. The inability of such cross-linked polymers to be remelted once cured implies that mechanical recycling processes used for thermoplastic materials do not translate to the recycling of thermoset polymers. Moreover, the structural diversity within the materials from the use of different monomers as well as the use of such polymers for the fabrication of fiber-reinforced polymer composites make recycling of these materials highly challenging. In this Perspective, depolymerization strategies for thermoset polymers are discussed with an emphasis on recent advancements within our group on recovering polymer building blocks from polyurethane (PU) and epoxy-based materials. While these two represent the largest thermoset polymer groups with respect to the production volumes, the recycling landscapes for these classes of materials are vastly different. For PU, increased collaboration between academia and industry has resulted in major advancements within solvolysis, acidolysis, aminolysis, and split-phase glycolysis for polyol recovery, where several processes are being evaluated for further scaling studies. For epoxy-based materials, the molecular skeleton has no obvious target for chemical scission. Nevertheless, we have recently demonstrated the possibility of the disassembly of the epoxy polymer in fiber-reinforced composites for bisphenol A (BPA) recovery through catalytic C−O bond cleavage. Furthermore, a base promoted cleavage developed by us and others shows tremendous potential for the recovery of BPA from epoxy polymers. Further efforts are still required for evaluating the suitability of such monomer recovery strategies for epoxy materials at an industrial scale. Nonetheless, recent advancements as illustrated with the presented chemistry suggest that the future of thermoset polymer recycling could include processes that emphasize monomer recovery in an energy efficient manner for closed-loop recycling.

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Section: Depolymerization Of Epoxy Polymersmentioning

confidence: 99%

Section: ■ Depolymerization Of Epoxy Polymersmentioning

confidence: 99%

Perspective on the Development of Monomer Recovery Technologies from Plastics Designed to Last

Kristensen,

Ahrens,

Donslund

et al. 2024

ACS Org. Inorg. Au

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“…Nickel-catalyzed hydrogenolysis of epoxy resins produces BPA in 66% isolated yield from a diamine-cured epoxy resin (Scheme C) . NaOH or KO t Bu can mediate the degradations of epoxy resins to yield BPA in up to 81% and 71% yield, respectively (Scheme D and 10E). , Lastly, a photocatalytic method with an acridine photocatalyst converts thiol-cured epoxy resins into BPA (Scheme F) . The reaction operates through a proton-coupled electron transfer (PCET) mechanism, which promotes C–C cleavage through β-scission.…”

Section: Commodity Plastics and Their Spi Codesmentioning

confidence: 99%

Industrial and Laboratory Technologies for the Chemical Recycling of Plastic Waste

Chin,

Diao

2024

ACS Catal.

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Synthetic polymers play an indispensable role in modern society, finding applications across various sectors ranging from packaging, textiles, and consumer products to construction, electronics, and industrial machinery. Commodity plastics are cheap to produce, widely available, and versatile to meet diverse application needs. As a result, millions of metric tons of plastics are manufactured annually. However, current approaches for the chemical recycling of postconsumer plastic waste, primarily based on pyrolysis, lag in efficiency compared to their production methods. In recent years, significant research has focused on developing milder, economically viable methods for the chemical recycling of commodity plastics, which involves converting plastic waste back into monomers or transforming it into other valuable chemicals. This Perspective examines both industrial and cutting-edge laboratory-scale methods contributing to recent advancements in the field of chemical recycling.

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“…Cross-linked epoxy resin, a type of thermoset resin, forms a three-dimensional network structure upon curing epoxy with hardeners such as anhydrides and amines . The reaction between epoxy and these hardeners generates hydroxyl groups, potentially enhancing the material’s overall polarity. , However, increased polarity and moisture absorption rates resulting from this can adversely impact dielectric properties, rendering such materials unsuitable for high-performance electronic packaging materials. , The introduction of an active ester, characterized by the Ph–O–CO– structure, as an epoxy hardener offers a unique pathway .…”

Section: Introductionmentioning

confidence: 99%

Curing Behavior and Properties of Active Ester Cured Cycloaliphatic Epoxy Resins

Liu,

Qin,

Cui

et al. 2024

Ind. Eng. Chem. Res.

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Cycloaliphatic epoxy resins are known for their synthesis process that eliminates hydrolyzable chlorine, thus avoiding the hydrolysis of hydrolyzable chlorine to hydroxyl groups in conventional epoxies, which is very favorable for the preparation of low dielectric epoxy resins. The curing process using active ester generates no hydroxyl groups, also indicating a promising approach for producing low dielectric epoxy resins. However, the resistance of cycloaliphatic epoxy to nucleophilic reactions restricts it from reacting usually only with anhydrides. This study investigates the reactivity of the active ester with cycloaliphatic epoxy, demonstrating its capability to undergo complete curing reactions at temperatures near 150 °C. Factors influencing this process, including the volatilization of the catalyst DMAP and its reactivity, are examined. Two types of cycloaliphatic epoxies (3,4-epoxycyclohexylmethyl-3′,4'-epoxycyclohexane carboxylate (EEC) and bis (3,4-epoxycyclohexylmethyl) adipate (BEA)) are combined with an active ester hardener, triacetyl resveratrol (TAR), to prepare epoxy resins. The activation energies for the curing reactions are determined, and the optimal concentration of catalyst 4-dimethylaminopyridine (DMAP) is identified for each resin. The use of catalysts at specific concentrations results in resins with superior mechanical properties (91.7 and 71.4 MPa for EEC/TAR and BEA/TAR), excellent thermal stability (T d5% of 354 and 347 °C), and good dielectric properties (dielectric constant of 3.68 and 3.95 at 10 MHz), outperforming anhydride-cured cycloaliphatic epoxy resins. These findings expand the selection of hardeners for cycloaliphatic epoxy resins and highlight the potential of the prepared resins in electronic packaging materials, offering enhanced properties suitable for various applications.

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Base-Mediated Depolymerization of Amine-Cured Epoxy Resins

Cited by 9 publications

References 29 publications

Perspective on the Development of Monomer Recovery Technologies from Plastics Designed to Last

Perspective on the Development of Monomer Recovery Technologies from Plastics Designed to Last

Industrial and Laboratory Technologies for the Chemical Recycling of Plastic Waste

Curing Behavior and Properties of Active Ester Cured Cycloaliphatic Epoxy Resins

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