Advances in sustainable thermosetting resins: From renewable feedstock to high performance and recyclability

Revealing the Dynamics of Sustainable Epoxy-Acrylate Networks from Recycled Plastics Blends and Oligomeric Lignin Precursors

The pursuit of carbon circularity in the fabrication of new materials has driven the increased use of recycled and biobased resources, a practice that has become more prevalent in recent years. In epoxy resin systems, alternatives to the use of fossil-based bisphenols have been proposed such as via the production of recycled bisphenol A (r-BPA) or by substitution with lignin derivatives, both of which are recovered from previous processes, promoting circularity. For this study, r-BPA was obtained via the chemical recycling of plastic blends from end-of-life (eol) televisions (TV). Subsequent glycidylation with epichlorohydrin (ECH) and ring-opening using acrylic acid allowed to obtain recycled bisphenol A diglycidyl ether (r-DGEBA) and bisphenol A glycerolate diacrylate (r-DAGBA), respectively. Six thermosets were fabricated by reacting Jeffamine D230 (Jeff D230) with r-DGEBA/r-DAGBA in a diverse range of epoxide:acrylate (E : A) ratios. The addition of acrylates resulted in the formation of β-amino esters (via Aza-Michael addition), which are thermo-reversible and allow the incorporation of dynamic bonds into the otherwise robust epoxy formulation. To evaluate the effect of the increasing biobased content, glycidylated depolymerized lignin (GDL) from hardwood was incorporated into the composition to produce five extra polymers. The crosslinked networks of these materials were extensively characterized, and the structure-property relationship was established by comparing their thermomechanical performance. The dissociative acrylate-amine interactions were identified under specific thermal conditions, applied systematically to program temporary shapes and analyse the crosslink reversibility of the thermosets. In summary, our findings demonstrate that recycled and biobased aromatic monomers can be incorporated to create dynamic crosslinked structures with tuneable properties, representing a step forward towards versatile, reusable, and circular materials.

Biomass-Based Functional Composite Resins with Recyclable and Shape Memory Properties

A key challenge in developing advanced functional thermosets lies in designing molecular architectures capable of integrating different specific performances into one material to meet diverse application demands. Here, a chitosan-derived trifunctional compound containing maleimide groups was used to directly cross-link tung oil-based polymer for fabricating multifunctional composite bioresins with reversible Diels-Alder bonds. The reversible cross-linking networks within resins were featured with stress relaxation, thermal reprocessability, and recyclability. The retro D-A reaction at relatively high temperatures provided the dynamic characteristics of the resins while ensuring their dimensional stability. Moreover, chitosan enhanced the mechanical properties of the resins while forming supramolecular hydrogen bonds via its abundant amino/hydroxyl groups, realizing shape memory of the resins. Furthermore, the synergistic interaction between chitosan functional groups and hydrogen bonding also imparted proton conductivity to the resins. This work provided a molecular design paradigm that harmonizes multifunctional integration in fully biomass resins, aiming for high-value applications.

Life cycle assessment of glass fibre versus flax fibre reinforced composite ship hulls

A comparative Life Cycle Assessment (LCA) was conducted between a recreational ship hull made of flax fibre-reinforced bio-based epoxy resin and a traditional ship hull made of glass fibre-reinforced polyester. Since small fibreglass boats pose an environmental problem after the end of life (EoL), the primary aim of this study was to evaluate the sustainability of the biocomposite material and identify recommendations for the future eco-design of recreational boats. The LCA study was developed according to the ISO 14,040 (ISO 14040, 2006), 14,044 (ISO 14044, 2006) methodology and the OpenLCA 2.0.4 software with the Ecoinvent v.3.9.1 database. Compared to the traditional one, the LCA of the biocomposite ship hull showed positive environmental impacts for all indicators except Terrestrial Ecotoxicity (TETP), which increased by 357% due to the use of fertilisers in flax production. Remarkably, the Global Warning Potential (GWP) decreased by 14%, the Human Toxicity Potential (HTP) diminished by 13%, and the Abiotic Depletion Potential (ADP) related to material resources was reduced by 75%. The sensitivity analysis shows that electricity consumption is the primary environmental impact driver for the FFRB ship hull. Thus, selecting renewable energy sources, such as solar or wind power, can significantly enhance sustainability. It is important to note that these impacts are influenced by the system and boundary conditions considered in the study. It was suggested that the local production of flax fibre and the use of recyclable bio-resin could improve the eco-design of the ship hull.

Synthesis of Renewable Furan-Based Benzoxazines and Polybenzoxazines: Recent Advances

The burgeoning field of materials science is currently witnessing a paradigm shift toward the utilization of renewable plant biomass as a viable chemical source for the production of sustainable materials. This trend is substantiated by a significant corpus of recent experimental and theoretical research focused on the synthesis and property analysis of such polymers. Within this context, polybenzoxazines stand out as a pioneering class of thermosetting polymers, distinguished by their exceptional thermal and mechanical characteristics, coupled with the feasibility of synthesizing their precursor monomers from eco-friendly, renewable resources, including plant phenols and furfurylamine. Opting for furfurylamine over traditional aniline and its petroleum-derived counterparts in the synthesis of benzoxazines not only increases the eco-compatibility of the resultant materials but also imparts a significant alteration to their properties. This short review, spanning the last three years, delves into the principal advancements achieved in the realm of novel furan-bearing benzoxazines and polybenzoxazines from 2021 to present, accentuating both the triumphs and challenges encountered in this burgeoning domain.

Synthesis and Characterization of Bio-based Polybenzoxazine Hybrids From Vanillin, Thymol, and Carvacrol

Recently, the fast advancement of bio-based polymers has boosted the interest in green and sustainable materials. In this context, polybenzoxazine-derived renewable resources have been widely investigated due to their environmental benefits and high mechanical and thermal properties. This study focused on synthesizing hybrid benzoxazines from bio-phenolic compounds- vanillin, thymol, and carvacrol- combined with Jeffamine D-230 and paraformaldehyde. The chemical structures of hybrid benzoxazines (Van-JD, Thy-JD, and Car-JD) were characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (1H NMR and 13C NMR). Furthermore, the curing behavior and thermal stability of synthesized bio-phenolic-based benzoxazines were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

Atomistic Modeling of Cross-Linking in Epoxy-Amine Resins: An Open-Source Protocol

Atomistic modeling has become an extensively used method for studying thermosetting polymers, particularly in the analysis and development of high-performance composite materials. Despite extensive research on the topic, a widely accepted, standardized, flexible, and open-source approach for simulating the cross-linking process from precursor molecules has yet to be established. This study proposes, tests, and validates a Molecular Dynamics (MD) protocol to simulate the cross-linking process of epoxy resins. We developed an in-house code based on Python and LAMMPS, enabling the generation of epoxy resin structures with high degrees of cross-linking. In our work, the epoxy network is dynamically formed within the MD simulations, modeling the chemical bonding process with constraints based on the distance between the reactive sites. To validate our model against experimental data from the literature, we then computed the density, thermal conductivity, and elastic response. The results show that the produced structures align well with experimental evidence, validating our method and confirming its feasibility for further analyses and in silico experiments. Beyond the case study presented in this work, focusing on bisphenol A diglycidyl ether (DGEBA) epoxy resin and diethylenetriamine (DETA) as curing agents in a 5:2 ratio, our approach can be easily adapted to investigate different epoxy resins.

Castor Oil-Based Epoxy Vitrimer Based on Dual Dynamic Network with Intrinsic Photothermal Self-Healing Capability

The development of sustainable epoxy vitrimers with outstanding mechanical strength and facile self-healing capabilities are of great significance for prolonging the lifespan and enhancing the reliability of electronic devices. In this study, we present a castor oil-derived epoxy vitrimer (ASB-ECO) featuring dual dynamic networks enabled by rationally designed ester-imine bonds and an aromatic Schiff base-conjugated crosslinker architecture. This molecular design strategy effectively enhances the mechanical properties of vegetable oil-based vitrimers and endows them with controllable self-healing capabilities under photothermal conversion. The 1.0-ASB-ECO system demonstrates dynamic characteristics with an activation energy (Ea) of 37.25 kJ/mol and a topological freezing transition temperature (Tv) of 123.13 °C. The material exhibits a photothermal conversion efficiency (ηPT = 61.42%) and can achieve a self-healing rate of 100% under visible-light radiation. In addition, 1.0-ASB-ECO displays a dielectric constant (Dk) of 5.54 and a loss tangent (Df) of 0.025 at 106 Hz. This study on biomass-based epoxy vitrimers presents a novel approach to developing electronic materials, achieving a combination of high mechanical performance, sustainability, and photothermal self-healing properties.

Research Progress on the Surface Modification of Basalt Fibers and Composites: A Review

Fiber-reinforced resin composites (FRRCs) are widely used in several fields such as construction, automotive, aerospace, and power. Basalt fiber (BF) has been increasingly used to replace artificial fibers such as glass fiber and carbon fiber in the production of BF-reinforced resin matrix composites (BFRRCs). This preference stems from its superior properties, including high temperature resistance, chemical stability, ease of manufacturing, cost-effectiveness, non-toxicity, and its natural, environmentally friendly characteristics. However, the chemical inertness of BF endows it with poor compatibility, adhesion, and dispersion in a resin matrix, leading to poor adhesion and a weak BF-resin interface. The interfacial bonding strength between BF and resin is an important parameter that determines the service performance of BFRRC. Therefore, the interfacial bonding strength between them can be improved through fiber modification, resin-matrix modification, mixed enhancers, etc., which consequently upgrade the mechanical properties, thermodynamic properties, and durability of BFRRC. In this review, first, the production process and properties of BFs are presented. Second, the mechanical properties, thermodynamic properties, and durability of BFRRC are introduced. Third, the modification effect of the non-destructive surface-modification technology of BF on BFRRC is presented herein. Finally, based on the current research status, the future research direction of BFRRC is proposed, including the development of high-performance composite materials, green manufacturing processes, and intelligent applications.

Epoxy Vitrimer with Excellent Mechanical Properties and High Tg for Detachable Structural Adhesives

It is a long-standing challenge for thermoset resins to simultaneously achieve outstanding thermomechanical and mechanical properties as well as rapid network reconfiguration due to the trade-off between chemical bond transformation and stability of the network. The design of the vitrimer network topology is an effective strategy to address the above issues. Here, we prepared an epoxy vitrimer material (DGEBA-API-MHHPA) with excellent mechanical properties and high glass-transition temperature (Tg) by introducing rigid-flexible integrated side chains [1-(3-aminopropyl) imidazole (API)], which endow DGEBA-API-MHHPA multiple interactions including "internal antiplasticization" effect, intermolecular hydrogen bonds, and π-π interactions. Moreover, the introduction of Zn2+ facilitates transesterification, enabling the fast rearrangement of the network. Specifically, the relaxation time of DGEBA-API0.2-MHHPA0.8-Zn reaches 65 s at 200 °C. Meanwhile, Zn2+-imidazole coordination bonds with energy dissipation improve the toughness of the vitrimer network. The resulting DGEBA-API0.2-MHHPA0.8-Zn exhibits self-healing and recyclable behaviors and possesses 80.3 MPa of tensile strength, 3.25 GPa of Young's modulus, 7.2 MPa·m1/2 of fracture toughness (KIC), and Tg of 129 °C. Concurrently, DGEBA-API0.2-MHHPA0.8-Zn can be applied as detachable structural adhesives for various substrates and can be used as matrixes of recyclable and electrically self-healing composites. This skillful strategy can be widely referenced in the large-scale manufacturing of high-performance dynamic covalent epoxy resins and their composites with excellent mechanical and thermomechanical performance.

Large-scale Conformational Changes of Diindole Functional Groups Driven by Cation-π Interactions and the Toughening Mechanism of Thermosets

This is described that a new concept for the design of toughening supramolecular thermosets by incorporating diindole groups, which are functionalized via cation-π interactions in covalently crosslinked networks. Large-scale conformational changes of the diindole functional groups could occur under external forces, endowing the thermosets with excellent toughening properties.

Epoxy-Based Vitrimers for Sustainable Infrastructure: Emphasizing Recycling and Self-Healing Properties

Epoxy-based vitrimers represent a paradigm shift in material science, offering an unprecedented combination of mechanical robustness, environmental sustainability, and reconfigurability. These dynamic polymer systems utilize associative dynamic covalent bonds (DCBs) such as transesterification to blend the structural integrity of thermosets with the recyclability and self-healing properties of thermoplastics. This unique combination makes vitrimers ideal candidates for high-performance applications in industries such as civil engineering, where material durability, repairability, and environmental compatibility are critical. Epoxy-based vitrimers, in particular, exhibit exceptional self-healing capabilities, allowing them to autonomously repair microcracks and damage, restoring mechanical properties under appropriate stimuli such as heat or light. Their recyclability further aligns with global sustainability goals by reducing material waste and lifecycle costs. Recent advancements have also integrated bio-based feedstocks and scalable manufacturing methods, enhancing the feasibility of these materials for industrial applications. This review explores the underlying self-healing mechanisms, dynamic recycling processes, and the emerging role of epoxy-based vitrimers in civil engineering. Challenges related to scalability, mechanical optimization, and regulatory acceptance are also discussed, with a focus on their potential to drive sustainable innovation in infrastructure materials.

From sugars to aliphatic amines: as sweet as it sounds? Production and applications of bio-based aliphatic amines

Aliphatic amines encompass a diverse group of amines that include alkylamines, alkyl polyamines, alkanolamines and aliphatic heterocyclic amines. Their structural diversity and distinctive characteristics position them as indispensable components across multiple industrial domains, ranging from chemistry and technology to agriculture and medicine. Currently, the industrial production of aliphatic amines is facing pressing sustainability, health and safety issues which all arise due to the strong dependency on fossil feedstock. Interestingly, these issues can be fundamentally resolved by shifting toward biomass as the feedstock. In this regard, cellulose and hemicellulose, the carbohydrate fraction of lignocellulose, emerge as promising feedstock for the production of aliphatic amines as they are available in abundance, safe to use and their aliphatic backbone is susceptible to chemical transformations. Consequently, the academic interest in bio-based aliphatic amines via the catalytic reductive amination of (hemi)cellulose-derived substrates has systematically increased over the past years. From an industrial perspective, however, the production of bio-based aliphatic amines will only be the middle part of a larger, ideally circular, value chain. This value chain additionally includes, as the first part, the refinery of the biomass feedstock to suitable substrates and, as the final part, the implementation of these aliphatic amines in various applications. Each part of the bio-based aliphatic amine value chain will be covered in this Review. Applying a holistic perspective enables one to acknowledge the requirements and limitations of each part and to efficiently spot and potentially bridge knowledge gaps between the different parts.

A universal strategy to design recyclable photocrosslinked networks via architecting lignin-derived spiro diacetal trigger

Precise transformation of renewable resources into high-performance photo-crosslinked resins with degradability remains a daunting challenge. In this work, we employed a renewable bioresource, lignin-derived vanillin, to construct a rigid spiro diacetal trigger, which was further coupled with thermosetting epoxy segments to develop three high-performance functionalized polymers. Several high-performance photosensitive materials with alkali-dissolving patterning and recyclable were innovatively engineered based on these polymers. The introduction of rigid spiro diacetal triggers, which function through a unique degradable mechanism under mildly acidic conditions, is expected to address the "seesaw" issue between high performance and degradability in photo-crosslinked networks. More importantly, the effect of spiro diacetal trigger on the thermo-mechanical properties and photopolymerization kinetics of thus-obtained photosensitive resins was systematically investigated. Consequently, the glass transition temperature and mechanical properties of the spiro diacetal-tailored naphthalene-type photosensitive resin (P-VPNE) are comparable to, or even exceed, those of competing materials. This work provides a universal strategy and valuable insights for the design and synthesis of high-performance degradable electronic packaging coatings, which are essential for a wide range of revolutionary technologies based on lignin derivatives.

Recent Development of Functional Bio-Based Epoxy Resins

The development of epoxy resins is mainly dependent on non-renewable petroleum resources, commonly diglycidyl ether bisphenol A (DGEBA)-type epoxy monomers. Most raw materials of these thermoset resins are toxic to the health of human beings. To alleviate concerns about the environment and health, the design and synthesis of bio-based epoxy resins using biomass as raw materials have been widely studied in recent decades to replace petroleum-based epoxy resins. With the improvement in the requirements for the performance of bio-based epoxy resins, the design of bio-based epoxy resins with unique functions has attracted a lot of attention, and bio-based epoxy resins with flame-retardant, recyclable/degradable/reprocessable, antibacterial, and other functional bio-based epoxy resins have been developed to expand the applications of epoxy resins and improve their competitiveness. This review summarizes the research progress of functional bio-based epoxy resins in recent years. First, bio-based epoxy resins were classified according to their unique function, and synthesis strategies of functional bio-based epoxy resins were discussed, then the relationship between structure and performance was revealed to guide the synthesis of functional bio-based epoxy resins and stimulate the development of more types of functional bio-based epoxy resins. Finally, the challenges and opportunities in the development of functional bio-based epoxy resins are presented.

UV-Mediated Facile Fabrication of a Robust, Fully Renewable and Controllably Biodegradable Poly(lactic acid)-Based Covalent Adaptable Network

A robust and fully biobased covalent adaptable network (CAN) that allows recyclability, biocompatibility, and controlled biodegradability is reported. The CAN was fabricated through a simple photo-cross-linking method, wherein low-molecular-weight poly(lactic acid) (∼3 kDa) was modified with end 1,2-dithiolane rings through a one-step Steglich esterification reaction with thioctic acid (TA). These incorporated 1,2-dithiolane rings undergo photoinduced ring-opening polymerization, thus enabling the cross-linking of poly(lactic acid) with abundant dynamic disulfide bonds. The resultant CAN demonstrates excellent transparency, effective UV-blocking capabilities below 320 nm, robust tensile strength (∼39 MPa), and superior dimensional stability at 80 °C, alongside attractive biocompatibility. Moreover, owing to the dynamic exchange and redox-responsiveness of disulfide bonds, the material can be recycled by hot-pressing and a reduction-oxidation process while also being capable of controllably biodegrading at the end of its lifecycle. Furthermore, it exhibits reconfigurable shape memory properties with fast recovery. This study elucidates a straightforward approach to fabricating multifunctional and sustainable polymer materials with potential applications in diverse fields such as packaging, coating, and biomedicine.

Bio-Based Thermosetting Resins: From Molecular Engineering to Intrinsically Multifunctional Customization

Recent years have witnessed a growing interest in bio-based thermosetting resins in terms of environmental concerns and the desire for sustainable industrial practices. Beyond sustainability, utilizing the structural diversity of renewable feedstock to craft bio-based thermosets with customized functionalities is very worthy of expectation. There exist many bio-based compounds with inherently unique chemical structures and functions, some of which are even difficult to synthesize artificially. Over the past decade, great efforts are devoted to discovering/designing functional properties of bio-based thermosets, and notable progress have been made in antibacterial, antifouling, flame retardancy, serving as carbon precursors, and stimuli responsiveness, among others, largely expanding their application potential and future prospects. In this review, recent advances in the field of functional bio-based thermosets are presented, with a particular focus on molecular structures and design strategies for discovering functional properties. Examples are highlighted wherein functionalities are facilitated by the inherent structures of bio-based feedstock. Perspectives on issues regarding further advances in this field are proposed at the end.

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

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.

Bio-Based Epoxy Vitrimers with Excellent Properties of Self-Healing, Recyclability, and Welding

The development of more recyclable materials is a key requirement for a transition towards a more circular economy. Thanks to exchange reactions, vitrimer, an attractive alternative for recyclable materials, is an innovative class of polymers that is able to change its topology without decreasing its connectivity. In this work, a bisphenol compound (VP) was prepared from saturated cardanol, i.e., 3-pentadecylphenol and vanillyl alcohol. Then, VP was epoxidized to obtain epoxide (VPGE). Finally, VPGE and citric acid (CA) were polymerized in the presence of catalyst TBD to prepare a fully bio-based vitrimer based on transesterification. The results from differential scanning calorimetry (DSC) showed that the VPGE/CA system could be crosslinked at around 163 °C. The cardanol-derived vitrimers had good network rearrangement properties. Meanwhile, because of the dynamic structural elements in the network, the material was endowed with excellent self-healing, welding, and recyclability.

Mismatched Supramolecular Interactions Facilitate the Reprocessing of Super-Strong and Ultratough Thermoset Elastomers

Thermoset elastomers have been extensively applied in many fields because of their excellent mechanical strengths and durable characteristics, such as an excellent chemical resistance. However, in the context of environmental issues, the nonrecyclability of thermosets has become a major barrier to the further development of these materials. Here, a well-tailored strategy is reported to solve this problem by introducing mismatched supramolecular interactions (MMSIs) into a covalently cross-linked poly(urethane-urea) network with dynamic acylsemicarbazide moieties. The MMSIs significantly strengthen and toughen the thermoset elastomer by effectively dissipating energy and resisting external stress. In addition, the elastomer recycling efficiency is improved 2.7-fold due to the superior reversibility of the MMSIs. The optimized thermoset elastomer features outstanding characteristics, including an ultrahigh tensile strength (110.8 MPa), an unprecedented tensile toughness (1245.2 MJ m-3), as well as remarkable resistance to chemical media, creep, and damage. Most importantly, it exhibits an extraordinary multirecyclability, and the 4th recycling efficiency remains close to 100%. This scalable method promotes the development of thermosets with both high performance and excellent recyclability, thereby providing valuable guidance for addressing the issue of nonrecyclability from a molecular design standpoint.

Closed-loop recycling of tough epoxy supramolecular thermosets constructed with hyperbranched topological structure

The regulation of topological structure of covalent adaptable networks (CANs) remains a challenge for epoxy CANs. Here, we report a strategy to develop strong and tough epoxy supramolecular thermosets with rapid reprocessability and room-temperature closed-loop recyclability. These thermosets were constructed from vanillin-based hyperbranched epoxy resin (VanEHBP) through the introduction of intermolecular hydrogen bonds and dual dynamic covalent bonds, as well as the formation of intramolecular and intermolecular cavities. The supramolecular structures confer remarkable energy dissipation capability of thermosets, leading to high toughness and strength. Due to the dynamic imine exchange and reversible noncovalent crosslinks, the thermosets can be rapidly and effectively reprocessed at 120 °C within 30 s. Importantly, the thermosets can be efficiently depolymerized at room temperature, and the recovered materials retain the structural integrity and mechanical properties of the original samples. This strategy may be employed to design tough, closed-loop recyclable epoxy thermosets for practical applications.

Sustainable Supramolecular Polymers

Polymer waste is a pressing issue that requires innovative solutions from the scientific community. As a beacon of hope in addressing this challenge, the concept of sustainable supramolecular polymers (SSPs) emerges. This article discusses challenges and efforts in fabricating SSPs. Addressing the trade-offs between mechanical performance and sustainability, the ultra-tough and multi-recyclable supramolecular polymers are fabricated via tailoring mismatched supramolecular interactions. Additionally, the healing of kinetically inert polymer materials is realized through transient regulation of the interfacial reactivity. Furthermore, a possible development trajectory for SSPs is proposed, and the transient materials can be regarded as the next generation in this field. The evolution of SSPs promises to be a pivotal stride towards a regenerative economy, sparking further exploration and innovation in the realm of sustainable materials.

Sustainable Vat Photopolymerization-Based 3D-Printing through Dynamic Covalent Network Photopolymers

Vat photopolymerization (VPP) based three-dimensional (3D) printing, including stereolithography (SLA) and digital light projection (DLP), is known for producing intricate, high-precision prototypes with superior mechanical properties. However, the challenge lies in the non-recyclability of covalently crosslinked thermosets used in these printing processes, limiting the sustainable utilization of printed prototypes. This review paper examines the recently explored avenue of VPP 3D-printed dynamic covalent network (DCN) polymers, which enable reversible crosslinks and allow for the reprocessing of printed prototypes, promoting sustainability. These reversible crosslinks facilitate the rearrangement of crosslinked polymers, providing printed polymers with chemical/physical recyclability, self-healing capabilities, and degradability. While various mechanisms for DCN polymer systems are explored, this paper focuses solely on photocurable polymers to highlight their potential to revolutionize the sustainability of VPP 3D printing.

Dynamic Thermosetting Resins with Synergistic Enhanced Strength and Toughness through Combination with Rigid and Soft Microdomains

Preparation of materials that possess highly strong and tough properties simultaneously is a great challenge. Thermosetting resins as a type of widely used polymeric materials without synergistic strength and toughness limit their applications in some special fields. In this report, an effective strategy to prepare thermosetting resins with synergistic strength and toughness, is presented. In this method, the soft and rigid microspheres with dynamic hemiaminal bonds are fabricated first, followed by hot-pressing to crosslink at the interfaces. Specifically, the rigid or soft microspheres are prepared via precipitation polymerization. After hot-pressing, the resulting rigid-soft blending materials exhibit superior strength and toughness, simultaneously. As compared with the precursor rigid or soft materials, the toughness of the rigid-soft blending films (RSBFs) is improved to 240% and 2100%, respectively, while the strength is comparable to the rigid precursor. As compared with the traditional crushing, blending, and hot-pressing of rigid or soft materials to get the nonuniform materials, the strength and toughness of the RSBFs are improved to 168% and 255%, respectively. This approach holds significant promise for the fabrication of polymer thermosets with a unique combination of strength and toughness.

Preparation, characterization, and application of waterborne lignin-based epoxy resin as eco-friendly wood adhesive

A series of novel waterborne lignin-based epoxy resin emulsions (WLEPs) were successfully synthesized, and then the WLEPs were cured with polyamide (PA) to give formaldehyde-free wood adhesives with high-performance. The chemical structures and properties of WLEP emulsions were determined. The effects of the emulsifiers on thermal and mechanical properties of the adhesives were investigated, and the potential application of WLEPs in the formulation of plywood were also evaluated. The results demonstrated that the WLEP dispersions presented excellent storage stability (>180 days) with their viscosities range from 110 mPa·s to 470 mPa·s and particle sizes in the range of 321-696 nm, which were beneficial for the fluidity and permeability of the wood adhesives. Furthermore, the thermal and mechanical properties of adhesives could be tuned effectively by controlling the length of PEG chains. The adhesive bearing PEG 6000 exhibited the highest tensile strength of 24.0 MPa and Young's modulus of 1439 MPa. Notably, the plywood prepared with the resulting adhesives displayed good bonding performance, especially water resistance, which were much higher than the national standard requirement for exterior-grade plywood type I. These results indicated that the WLEPs could be used as sustainable alternatives for traditional formaldehyde-based wood adhesives in practical applications.

Investigation of Phenolic Resin-Modified Asphalt and Its Mixtures

This study comprehensively examines the influence of phenol-formaldehyde resin (PF) on the performance of base asphalt and its mixtures for road applications, emphasizing its innovative use in enhancing pavement quality. Optimal PF content was determined through the evaluation of standard indicators and rotational viscosity. In-depth analyses of PF-modified asphalt's high- and low-temperature rheological properties and viscoelastic behavior were conducted using dynamic shear rheometers and bending beam rheometers. Aging resistance was assessed through short-term aging and performance grade (PG) grading. Moreover, Marshall and water stability tests were performed on PF-modified asphalt mixtures. Findings indicate that the uniform dispersion of PF particles effectively inhibits asphalt flow at high temperatures, impedes oxygen penetration, and delays the transition from elasticity to viscosity. These unique properties enhance the high-temperature stability, rutting resistance, and aging resistance of PF-modified asphalt. However, under extremely low temperatures, PF's brittleness may impact asphalt flexibility. Nonetheless, the structural advantages of PF-modified asphalt, such as improved mixture density and stability, contribute to enhanced high-temperature performance, water stability, adhesion, and freeze-thaw cycle stability. This research demonstrates the feasibility and effectiveness of using PF to enhance the overall performance of base asphalt and asphalt mixtures for road construction.

Biomass- and Carbon Dioxide-Derived Polyurethane Networks for Thermal Interface Material Applications

Recent environmental concerns have increased demand for renewable polymers and sustainable green resource usage, such as biomass-derived components and carbon dioxide (CO2). Herein, we present crosslinked polyurethanes (CPUs) fabricated from CO2- and biomass-derived monomers via a facile solvent-free ball milling process. Furan-containing bis(cyclic carbonate)s were synthesized through CO2 fixation and further transformed to tetraols, denoted FCTs, by aminolysis and utilized in CPU synthesis. Highly dispersed polyurethane-based hybrid composites (CPU-Ag) were also manufactured using a similar ball milling process. Due to the malleability of the CPU matrix, enabled by transcarbamoylation (dynamic covalent chemistry), CPU-based composites are expected to present very low interfacial thermal resistance between the heat sink and heat source. The characteristics of the dynamic covalent bond (i.e., urethane exchange reaction) were confirmed by the results of dynamic mechanical thermal analysis and stress relaxation analysis. Importantly, the high thermal conductivity of the CPU-based hybrid material was confirmed using laser flash analysis (up to 51.1 W/m·K). Our mechanochemical approach enables the facile preparation of sustainable polymers and hybrid composites for functional application.

Fully bio-based epoxy resins from lignin and epoxidized soybean oil: Rigid-flexible, tunable properties and high lignin content

The application of epoxidized soybean oil (ESO) in thermosetting polymers is impeded by its unsatisfactory thermomechanical properties. Here, in order to address the limitation, technical lignin was modified by tung oil anhydride and then used as the hardener to compensate for the inherent flexibility defects of ESO thermosets (TLs). As the lignin content increased, a notable improvement in the activation energy of TLs was observed, attributed to the restraining effect of lignin's rigid structure on segmental relaxation. Concurrently, the tensile strength of TLs increased from 2.8 MPa to 34.0 MPa, concomitant with a decrease in elongation at break from 32.9 % to 8.0 %. Comparative analysis with TL-0 (devoid of lignin) demonstrated substantial enhancements in glass transition temperature, shape fixation ratio, and shape recovery ratio for TL-50 (comprising 50 wt% of lignin), elevating from 16.9 °C, 89.1 %, and 89.5 % to 118.6 °C, 94.0 %, and 99.3 %, respectively. These results unequivocally highlight the favorable dynamic mechanical and shape memory properties conferred upon TLs by lignin addition. While the introduction of lignin adversely affected thermal stability, a notable improvement in char yield (800 °C) was observed. Collectively, these findings underscore the potential of technical lignin as a promising bio-based curing agent for ESO.

Hyperbranched Dynamic Crosslinking Networks Enable Degradable, Reconfigurable, and Multifunctional Epoxy Vitrimer

Degradation and reprocessing of thermoset polymers have long been intractable challenges to meet a sustainable future. Star strategies via dynamic cross-linking hydrogen bonds and/or covalent bonds can afford reprocessable thermosets, but often at the cost of properties or even their functions. Herein, a simple strategy coined as hyperbranched dynamic crosslinking networks (HDCNs) toward in-practice engineering a petroleum-based epoxy thermoset into degradable, reconfigurable, and multifunctional vitrimer is provided. The special characteristics of HDCNs involve spatially topological crosslinks for solvent adaption and multi-dynamic linkages for reversible behaviors. The resulting vitrimer displays mild room-temperature degradation to dimethylacetamide and can realize the cycling of carbon fiber and epoxy powder from composite. Besides, they have supra toughness and high flexural modulus, high transparency as well as fire-retardancy surpassing their original thermoset. Notably, it is noted in a chance-following that ethanol molecule can induce the reconstruction of vitrimer network by ester-exchange, converting a stiff vitrimer into elastomeric feature, and such material records an ultrahigh modulus (5.45 GPa) at -150 °C for their ultralow-temperature condition uses. This is shaping up to be a potentially sustainable advanced material to address the post-consumer thermoset waste, and also provide a newly crosslinked mode for the designs of high-performance polymer.

Amphiphilic Polyoxazoline Copolymer-Imidazole Complexes as Tailorable Thermal Latent Curing Agents for One-Component Epoxy Resins

One-component epoxy resins (OCERs) are proposed to overcome the energy inefficiency and processing difficulties of conventional two-component epoxy resins by employing latent curing agents, specifically thermal latent curing agents (TLCs). Despite recent progress, the need for TLCs with a simple preparation method for different curing agents, epoxy resins, and process conditions remains. Here, tailorable TLCs were prepared by forming complexes between imidazole (Im) and amphiphilic polyoxazoline copolymers with tunable structures and properties by a solvent evaporation method. The obtained TLCs were manually mixed with DGEBA to prepare OCERs. The miscibility of the complexes with DGEBA was studied, considering the functionalities of copolymers. The curing behaviors of TLCs were compared using dynamic Differential Scanning Calorimetry (DSC) studies considering the side chain and composition of the copolymers, copolymer:Im ratio, and concentration of Im in DGEBA. The curing behavior of the promising OCERs was studied by isothermal DSC studies to investigate their stability at different temperatures and curing rate at elevated temperatures revealing the stability of these OCERs.

Pulsed laser welding of macroscopic 3D graphene materials

Welding is a key missing manufacturing technique in graphene science. Due to the infusibility and insolubility, reliable welding of macroscopic graphene materials is impossible using current diffusion-bonding methods. This work reports a pulsed laser welding (PLW) strategy allowing for directly and rapidly joining macroscopic 3D porous graphene materials under ambient conditions. Central to the concept is introducing a laser-induced graphene solder converted from a designed unique precursor to promote joining. The solder shows an electrical conductivity of 6700 S m-1 and a mechanical strength of 7.3 MPa, over those of most previously reported porous graphene materials. Additionally, the PLW technique enables the formation of high-quality welded junctions, ensuring the structural integrity of weldments. The welding mechanism is further revealed, and two types of connections exist between solder and base structures, i.e., intermolecular force and covalent bonding. Finally, an array of complex 3D graphene architectures, including lateral heterostructures, Janus structures, and 3D patterned geometries, are fabricated through material joining, highlighting the potential of PLW to be a versatile approach for multi-level assembly and heterogeneous integration. This work brings graphene into the laser welding club and paves the way for the future exploration of the exciting opportunities inherent in material integration and repair.

Sustainable Bio-Based Epoxy Resins with Tunable Thermal and Mechanic Properties and Superior Anti-Corrosion Performance

Bio-based epoxy thermoset resins have been developed from epoxidized soybean oil (ESO) cured with tannic acid (TA). These two substances of vegetable origin have been gathering attention due to their accessibility, favorable economic conditions, and convenient chemical functionalization. TA's suitable high phenolic functionalization has been used to crosslink ESO by adjusting the -OH (from TA):epoxy (from ESO) molar ratio from 0.5:1 to 2.5:1. By means of Fourier-transform infrared spectroscopy, resulting in thermosets that evidenced optimal curing properties under moderate conditions (150-160 °C). The thermogravimetric analysis of the cured resins showed thermal stability up to 261 °C, with modulable mechanical and thermal properties determined by differential scanning calorimetry, dynamical mechanical thermal analysis, and tensile testing. Water contact angle measurements (83-87°) and water absorption tests (0.6-4.5 initial weight% intake) were performed to assess the suitability of the resins as waterproof coatings. Electrochemical impedance spectroscopy measurements were performed to characterize the anti-corrosive capability of these coatings on carbon steel substrates. Excellent barrier properties have been demonstrated due to the high electrical isolation and water impermeability of these oil-based coatings, without signs of deterioration over 6 months of immersion in a 3.5 wt.% NaCl solution. These results demonstrate the suitability of the developed materials as anti-corrosion coatings for specific applications.

Itaconic Acid as a Comonomer in Betulin-Based Thermosets via Sequential and Bulk Preparation

The inherent chemical functionalities of biobased monomers enable the production of renewably sourced polymers that further advance sustainable manufacturing. Itaconic acid (IA) is a nontoxic, commercially produced biobased monomer that can undergo both UV and thermal curing. Betulin is a biocompatible, structurally complex diol derived from birch tree bark that has been recently studied for materials with diverse applications. Here, betulin, IA, and biobased linear diacids, 1,12-dodecanedioic acid (C12) and 1,18-octadecanedioic acid (C18), were used to prepare thermosets using sequential and bulk curing methods. Thermoplastic polyester precursors were synthesized and formulated into polyester-methacrylate (PM) resins to produce sequential UV-curable thermosets. Bulk-cured polyester thermosets were prepared using a one-pot, solventless melt polycondensation using glycerol as a cross-linker. The structure-property relationships of the thermoplastic polyester precursors, sequentially prepared PM thermosets, and bulk-cured polyester thermosets were evaluated with varying IA content. Both types of thermosets exhibited higher storage moduli, Tgs, and thermal stabilities with greater IA comonomer content. These results demonstrate the viability of using IA as a comonomer to produce betulin-based thermosets each with tunable properties, expanding the scope of their applications and use in polymeric materials.

Preparation and Application of a Multifunctional Interfacial Modifier for Ramie Fiber/Epoxy Resin Composites

A multi-functional modifier, which could improve the mechanical and thermal performance simultaneously, is significant in composites production. Herein, inspired by the chemistry of mussel, an interfacial modifier named FPD was designed and synthesized through one simple step, which was attached by three functional groups (including catechol, N-H bond, and DOPO). Due to the innate properties of each functional group, FPD played multiple roles: adhere to the ramie fibers from catechol and cure with the epoxy resin from -NH-, an antiflaming property from DOPO, and the compatibilizer between ramie fibers and epoxy resin was also improved by changing the polarity of ramie fiber. All of the above functions can be proved by means of water contact angle (WCA), atomic force microscope (AFM), and scanning electron microscopy (SEM), etc. After solidification, the ramie fiber/epoxy composites demonstrated superior performances in terms of good mechanical properties and excellent flame retardant property. With the addition of 30 wt.% FPD, the tensile strength and modulus of the ramie/epoxy composite showed an improvement of 37.1% and 60.9%, and flexural strength and modulus of the composite were improved by 8.9% and 19.3% comparing with no addition composite. Moreover, the composite could achieve the goal for V-0 rating in the UL-94 test and LOI value was 34.6% when the addition of FPD reached 30 wt.%. This work provided us with an efficient method for fabricating nature fiber/epoxy composites with good properties.

Reprocessible Triketoenamine-Based Vitrimers with Closed-Loop Recyclability

Development of thermosets that can be repeatedly recycled via both chemical route (closed-loop) and thermo-mechanical process is attractive and remains an imperative task. In this work, we reported a triketoenamine based dynamic covalent network derived from 2,4,6-triformylphloroglucinol and secondary amines. The resulting triketoenamine based network does not have intramolecular hydrogen bonds, thus reducing its π-electron delocalization, lowering the stability of the tautomer structure, and enabling its dynamic feature. By virtue of the highly reversible bond exchange, this novel dynamic covalent bond enables the easy construction of highly crosslinked and chemically reprocessable networks from commercially available monomers. The as-made polymer monoliths exhibit high mechanical properties (tensile strength of 79.4 MPa and Young's modulus of 571.4 MPa) and can undergo a monomer-network-monomer (yields up to 90 %) recycling mediated by an aqueous solution, with the new-generation polymer capable of restoring the material strength to its original state. In addition, owing to its dynamic nature, a catalyst-free and low-temperature reprogrammable covalent adaptable network (vitrimer) was achieved. The design concept reported herein can be applied to the development of other novel vitrimers with high repressibility and recyclability, and sheds light on future design of sustainable polymers with minimal environmental impact.

Robust Vanillin-Derived Poly(thioether imidazoles) as Both a Latent Curing and Toughening Agent for One-Component Epoxy Resins

One-component epoxy resins based on latent curing agents have garnered research attention owing to their outstanding storage stability and excellent processability, while their development considerably depends on the design and preparation of sustainable latent curing agents. Herein, taking structural advantage of lignin-derived vanillin, a biobased polymerizable aromatic imidazole monomer with α,ω-diene functionality was designed and prepared, which was applicable in subsequent thiol-ene polymerization, yielding a series of robust poly(thioether imidazoles) with excellent tunability of the structure and properties. The findings indicated that the precursors comprising poly(thioether imidazole) and commercially available epoxy resins could keep their fluidity at 25 °C for over 90 days and rapidly cured into resins under elevated temperature, demonstrating that the poly(thioether imidazole) can serve as both a latent curing and toughening agent for one-component epoxy resins because of homopolymerization initiated by imidazole groups and the introduction of an aliphatic chain in the as-prepared poly(thioether imidazole) matrix.

Sustainable Alternatives for the Development of Thermoset Composites with Low Environmental Impact

The current concerns of both society and the materials industries about the environmental impact of thermoset composites, as well as new legislation, have led the scientific sector to search for more sustainable alternatives to reduce the environmental impact of thermoset composites. Until now, to a large extent, sustainable reinforcements have been used to manufacture more sustainable composites and thus contribute to the reduction of pollutants. However, in recent years, new alternatives have been developed, such as thermosetting resins with bio-based content and/or systems such as recyclable amines and vitrimers that enable recycling/reuse. Throughout this review, some new bio-based thermoset systems as well as new recyclable systems and sustainable reinforcements are described, and a brief overview of the biocomposites market and its impact is shown. By way of conclusion, it should be noted that although significant improvements have been achieved, other alternatives ought to be researched.

Comparison of the Properties of Epoxy Resins Containing Various Trifluoromethyl Groups with Low Dielectric Constant

A series of epoxy resins containing various trifluoromethyl groups were synthesized and thermally cured with diaminodiphenylmethane (DDM) and aminophenyl sulfone (DDS). All epoxy resins exhibited excellent thermal stability with the glass transition temperatures of above 128 °C and 5% weight loss temperatures of above 300 °C. DDS-cured epoxy resins possessed higher thermal stability than that of DDM-cured epoxy resins, while DDM-cured epoxy resins showed better mechanical, dielectric, and hydrophobic properties. Additionally, DDM-cured epoxy resins with different locations and numbers of trifluoromethyl groups showed flexural strength in the range of 95.55~152.36 MPa, flexural modulus in the range of 1.71~2.65 GPa, dielectric constant in the range of 2.55~3.05, and water absorption in the range of 0.49~0.95%. These results indicate that the incorporation of trifluoromethyl pendant groups into epoxy resins can be a valid strategy to improve the dielectric and hydrophobic performance.

Contribution of the Surface Treatment of Nanofibrillated Cellulose on the Properties of Bio-Based Epoxy Nanocomposites Intended for Flexible Electronics

The growing interest in materials derived from biomass has generated a multitude of solutions for the development of new sustainable materials with low environmental impact. We report here, for the first time, a strategy to obtain bio-based nanocomposites from epoxidized linseed oil (ELO), itaconic acid (IA), and surface-treated nanofibrillated cellulose (NC). The effect of nanofibrillated cellulose functionalized with silane (NC/S) and then grafted with methacrylic acid (NC/SM) on the properties of the resulted bio-based epoxy systems was thoroughly investigated. The differential scanning calorimetry (DSC) results showed that the addition of NCs did not influence the curing process and had a slight impact on the maximum peak temperature. Moreover, the NCs improved the onset degradation temperature of the epoxy-based nanocomposites by more than 30 °C, regardless of their treatment. The most important effect on the mechanical properties of bio-based epoxy nanocomposites, i.e., an increase in the storage modulus by more than 60% at room temperature was observed in the case of NC/SM addition. Therefore, NC's treatment with silane and methacrylic acid improved the epoxy-nanofiber interface and led to a very good dispersion of the NC/SM in the epoxy network, as observed by the SEM investigation. The dielectric results proved the suitability of the obtained bio-based epoxy/NCs materials as substitutes for petroleum-based thermosets in the fabrication of flexible electronic devices.

Direct Conversion of Liquid Organic Precursor into 3D Laser-Induced Graphene Materials

Among the different states of matter, liquids have particular advantages in terms of easy handling and recycling, which has been manifested in various chemosynthetic reactions, but remains underexplored in graphene synthesis. This work reports the direct conversion of liquid organic precursor into versatile 3D graphene materials using rapid laser irradiation. The liquid precursor allows for easy fabrication of graphene with significant 3D architectures, including powders, patterned composite structures, and substrate-free films. Taking advantage of the high compatibility of liquid precursor with a wide range of dopants, the 3D graphene can be further engineered together with various functional components, especially the high loading (≈15 wt.%) and well-dispersed (an average diameter of less than 50 nm) high-entropy alloy nanoparticles. Furthermore, combined with the 3D printing strategy, the rapid construction of graphene with complex and accurate 3D shapes is demonstrated via a selective in situ laser transforming (SLT) strategy. With the high structural integrity unachievable by traditional 3D printing methods, the obtained objects show an electrical conductivity of 4380 S m^-1 and a compressive modulus of 31.8 MPa. The results reported in this work will open up a new way for the fabrication of functional carbon materials with customizable shapes and components.

Ring-Opening Oligomerization Mechanism of a Vanillin-Furfurylamine-Based Benzoxazine and a Mono-Azomethine Derivative

Exploring the ring-opening polymerization (ROP) mechanism of benzoxazines is a fundamental issue in benzoxazine chemistry. Though some research papers on the topic have been reported, the ROP mechanism of mono-benzoxazines is still elusive. The key point for mechanistic studies is to determine and characterize the structure and formation pathways of the products generated in ROP. In this paper, the ROP of a vanillin-furfurylamine-based benzoxazine and a mono-azomethine derivative is studied with differential scanning calorimetry, fourier transform infrared spectroscopy, nuclear magnetic resonance, and electrospray ionization mass spectrometry, respectively. The results show that the products consist of a range of cationic species, zwitterions, fragments, and series of cyclic and linear oligomers of varying molecular sizes. It is proposed that both mono-benzoxazines undergo thermally activated cationic ring-opening oligomerization via zwitterion intermediates. Upon thermal induction, multi-bond-cleavage takes place to form various zwitterionic intermediates, which react with a monomer, a fragment, or a second zwitterion by several pathways to generate cyclic and linear oligomers.

Self-Healable, Malleable, Ecofriendly Recyclable and Robust Polyimine Thermosets Derived from Trifluoromethyl Diphenoxybenzene Backbones

Dynamic covalent chemistry opens up great opportunities for a sustainable society by producing reprocessable networks of polymers and even thermosets. However, achieving the closed-loop recycling of polymers with high performance remains a grand challenge. The introduction of aromatic monomers and fluorine into covalent adaptable networks is an attractive method to tackle this challenge. Therefore, we present a facile and universal strategy to focus on the design and applications of polyimine vitrimers containing trifluoromethyl diphenoxybenzene backbones in applications of dynamic covalent polymers. In this study, fluorine-containing polyimine vitrimer networks (FPIVs) were fabricated, and the results revealed that the FPIVs not only exhibited good self-healability, malleability and processability without the aid of any catalyst, but also possessed decent mechanical strength, superior toughness and thermal stability. We hope that this work could provide a novel pathway for the design of high-performance polyimine vitrimers by recycling of plastic wastes.

Synthesis and Post-Functionalization of Poly(conjugated ester)s Based on 3-Methylene-1,5-dioxepan-2-one

Poly(α-methylene ester)s are an attractive type of functional aliphatic polyesters that represent a platform for the fabrication of various biodegradable and biomedical polymers. Herein, we report the controlled ring-opening polymerization (ROP) of a seven-membered α-methylene lactone (3-methylene-1,5-dioxepan-2-one, MDXO) that was synthesized based on the Baylis-Hillman reaction. The chemoselective ROP of MDXO was catalyzed by diphenyl phosphate (DPP) at 60 °C or stannous octoate (Sn(Oct)₂) at 130 °C, generating α-methylene-containing polyester (PMDXO) with a linear structure and easily tunable molar mass. The ring-opening copolymerization of MDXO with ε-caprolactone or 1,5-dioxepan-2-one was also performed under the catalysis of DPP or Sn(Oct)₂ to afford copolymers with different compositions and sequence structures that are influenced by the kinds of monomers and catalysts. PMDXO is a slowly crystallizable polymer with a glass transition temperature of ca. -33 °C, and its melting temperature and enthalpy are significantly influenced by the thermal history. The thermal properties of the copolymers are dependent on their composition and sequence structure. Finally, the post-modification of PMDXO based on the thiol-Michael addition reaction was briefly explored using triethylamine as a catalyst. Given the optimized condition, PMDXO could be dually modified to afford biodegradable polyesters with different functionalities.

In-situ formed nanoscale Fe0 for fenton-like oxidation of thermosetting unsaturated polyester resin composites: Nondestructively recycle carbon fiber

Thermosetting unsaturated polyester resin (UPR) composites were found widespread industrial applications. However, the numerous stable carbon-carbon bonds in cross-linked networks made them intractable for degradation, causing the large-scale composite wastes. Here a nanoscale Fe⁰ catalyst in-situ forming strategy was exploited to nondestructively recycle carbon fiber (CF) from UPR composites via Fenton-like reaction. The nano-Fe⁰ catalyst employed in this strategy activated H₂O₂ for removing UPR, featuring mild conditions and efficient degradation ability. Aiming at facile growth of the catalyst, a porous UPR was achieved by the hydrolysis of alkalic system. The nanoscale Fe⁰ catalyst was subsequently formed in-situ on the surface of hydrolyzed resin by borohydride reduction. Benefiting from fast mass transfer, the in-situ grown nano-Fe⁰ showed more efficient degradation ability than added nano-Fe⁰ or Fe²⁺ catalyst during Fenton-like reaction. The experiments indicated that hydrolyzed resin could be degraded more than 90% within 80 min, 80 °C. GC-MS, FT-IR analysis and Density functional theory (DFT) calculation were conducted to explained the fracture processes of carbon skeleton in hydrolyzed resin. Especially, a remarkable recovery process of CF from composites was observed, with a 100 percent elimination of resin. The recycled CF cloth exhibited a 99% strength retention and maintained the textile structure, microtopography, chemical structure, resulting in the nondestructive reclaim of CF. This in-situ formed nanoscale Fe⁰ catalytic degradation strategy may provide a promising practical application for nondestructively recycle CF from UPR composites.