Recycling of thermosets and their composites

Ibarra, Rodolfo Morales

doi:10.1016/b978-0-08-101021-1.00020-4

Cited by 18 publications

(15 citation statements)

References 33 publications

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“…Yet this fixity comes at a pricethermosets are virtually unrecyclable except through use as filler materials or decomposition through specialized chemical approaches. 5 Considering the explosive growth of plastics waste resulting from difficulties in addressing end-of-life usage of polymeric materials, 6,7 there is a pressing need for a new generation of materials that can be reprocessed like thermoplastics yet still retain the beneficial properties of a crosslinked thermoset material. Such a material could have scarcely been realized by historical polymer chemistry, but the emergence of covalent adaptable networks (CANs) over the past two decades has both highlighted the power of modern polymer chemistry while also challenging the traditional understanding of thermoplastics and thermosets.…”

Section: Introductionmentioning

confidence: 99%

Adaptable Crosslinks in Polymeric Materials: Resolving the Intersection of Thermoplastics and Thermosets

et al. 2019

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The classical division of polymeric materials into thermoplastics and thermosets based on covalent network structure often implies that these categories are distinct and irreconcilable. Yet, the past two decades have seen extensive development of materials that bridge this gap through incorporation of dynamic crosslinks, enabling them to behave as both robust networks and moldable plastics. Although their potential utility is significant, the growth of covalent adaptable networks (CANs) has obscured the line between “thermoplastic” and “thermoset” and erected a conceptual barrier to the growing number of new researchers entering this discipline. This Perspective aims to both outline the fundamental theory of CANs and provide a critical assessment of their current status. We emphasize throughout that the unique properties of CANs emerge from the network chemistry, and particularly highlight the role that the crosslink exchange mechanism (i.e., dissociative exchange or associative exchange) plays in the resultant material properties under processing conditions. Predominant focus will be on thermally induced dynamic behavior, as the majority of presently employed exchange chemistries rely on thermal stimulus, and it is simple to apply to bulk materials. Lastly, this Perspective aims to identify current issues and address possible solutions for better fundamental understanding within this field.

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Section: Introductionmentioning

confidence: 99%

Adaptable Crosslinks in Polymeric Materials: Resolving the Intersection of Thermoplastics and Thermosets

et al. 2019

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“…Such a transition can be more clearly observed in the reduced relative MSD g 2 /⟨2R g/eff 2 ⟩. As shown in Figure 8d, as t > τ e , g 2 /⟨2R g/eff 2 ⟩ is close to the plateau value, implying the system enters a viscous liquid state. Moreover, the overlap parts are quantitatively in good agreement with the SRM predictions at T ref = 1.0 for b T G, b T G′, and g 2 /⟨2R g/eff 2 ⟩.…”

Section: ■ Introductionmentioning

confidence: 72%

Structure, Dynamics, and Rheology of Vitrimers

Xia,

Kalow,

Olvera de la Cruz

2023

Macromolecules

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Vitrimers are associative covalent adaptable networks that undergo reversible bond-exchange reactions while maintaining a fixed cross-linking density with changing temperature. To date, experimental studies that rely on macroscopic rheology have not been able to reveal topological changes and microscopic dynamics in these materials. Here, coarse-grained molecular dynamics simulations combined with a Monte Carlo method are implemented to investigate the topological structural changes, microscopic dynamics, and linear rheology of unentangled side-chain-linked vitrimers in conjunction with the sticky Rouse model (SRM). We find that there is a minor variation in the topological structure with temperature. The dynamic heterogeneities of the bond-exchange behavior and the system dynamics increase remarkably when approaching the topological freezing transition temperature T v . Quantitative agreement between the simulation results and the SRM predictions is observed for the stress relaxation, elastic and loss moduli, and the relative mean-squared displacement, especially at the intermediate- and long-time or low-frequency regimes, where the time–temperature superposition principle is satisfied. We obtain a scaling collapse curve for the dynamic bond relaxation time, the zero-shear viscosity, and the horizontal shift factors without introducing any parameters, suggesting that the microscopic and macroscopic dynamics exhibit a similar relaxation behavior even in the presence of loop defects. Moreover, these results are in good agreement with those predicted by the SRM, indicating that the linear rheology of unentangled vitrimers with a fast bond-exchange rate can be analyzed via a single-chain approach based on the SRM.

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“…Even though there are many valuable utilizations for thermoset composite materials, recycling at the end of the life cycle could also be a more complex issue [ 26 ]. Nonetheless, the perceived insufficiency of recyclability is increasingly essential and seen as a critical barrier for developing or even using composite materials in some markets.…”

Section: Difficulties With Composite Disposalmentioning

confidence: 99%

Recycling of Carbon Fiber-Reinforced Composites—Difficulties and Future Perspectives

Borjan

Knez

2021

Materials

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Carbon fiber-reinforced composites present an exciting combination of properties and offer clear advantages that make them a perfect replacement for a spread of materials. Consequently, in recent years, their production has dramatically increased as well as the quantity of waste materials. As future legislations are likely to prevent the use of landfills and incineration to dispose of composite waste, alternative solutions such as recycling are considered as one of the urgent problems to be settled. This study presents the leading technologies for recycling carbon fiber-reinforced composites, focusing on chemical recycling using sub- and supercritical fluids. These new reaction media have been demonstrated to be more manageable and efficient in recovering clean fibers with good mechanical properties. The conventional technologies of carbon fibers recycling have also been reviewed and described with both advantages and drawbacks.

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Recycling of thermosets and their composites

Cited by 18 publications

References 33 publications

Adaptable Crosslinks in Polymeric Materials: Resolving the Intersection of Thermoplastics and Thermosets

Adaptable Crosslinks in Polymeric Materials: Resolving the Intersection of Thermoplastics and Thermosets

Structure, Dynamics, and Rheology of Vitrimers

Recycling of Carbon Fiber-Reinforced Composites—Difficulties and Future Perspectives

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