Recent advances in bio-based epoxy resins and bio-based epoxy curing agents

Development of Halloysite Nanotube-Infused Thermoset Soybean Bio-Resin for Advanced Medical Packaging

The development of eco-friendly, mechanically stable, and biocompatible materials for medical packaging has gained significant attention in recent years. Halloysite nanotubes (HNTs) have emerged as a promising nanomaterial due to their unique tubular structure, high aspect ratio, and biocompatibility. We aim to develop a novel soybean oil-based thermoset bio-resin incorporating HNTs and to characterize its physical and functional properties for medical packaging. Soybean oil was epoxidized using an eco-friendly method and used as a precursor for preparing the thermoset resin (ESOR). Different amounts of HNTs (0.25, 0.50, and 1.0 wt.%) were used to prepare the ESOR/HNTs blends. Various characteristics such as transparency, tensile strength, thermal resistance, and water absorption were investigated. While incorporating HNTs improved the tensile strength and thermal properties of the ESOR, it noticeably reduced its transparency at the 1.0 wt.% level. Therefore, HNTs were modified using sodium hydroxide and (3-Aminopropyl) triethoxysilane (APTES) and ESOR/HNTs blends were made using 1.0 wt.% of modified HNTs. It was shown that modifying HNTs using NaOH improved the transparency and mechanical properties of prepared blends compared to those with the same amount of unmodified HNTs. However, modifying using (3-Aminopropyl) triethoxysilane (APTES) decreased the transparency but improved the water absorption of prepared resins. This study provides valuable insights into the design of HNT-based ESOR blends as a sustainable material for medical packaging, contributing to the advancement of eco-friendly packaging solutions in the healthcare industry.

Supported Ionic Liquid-Phase Materials (SILP) as a Multifunctional Group of Highly Stable Modifiers and Hardeners for Carbon and Flax Epoxy Composites

This paper introduces a novel approach to enhance epoxy resin formulations by using SILP materials as multifunctional hardeners and fillers in composite structures reinforced with carbon and flax fibers. This study explores the integration of ionic liquids (ILs) onto a silica support structure, presenting various permutations involving silica selection, ionic liquid choice, and concentration. The focus of this study was to elucidate the influence of SILP on resin curing ability and the mechanical properties of the resulting composites. Detailed research was conducted, including Brunauer-Emmett-Teller analysis (BET) for SILP materials and curing characterization for epoxy resin formulations with different SILP materials. Furthermore, the mechanical properties of the obtained composites were determined by Scanning Electron Microscopy analysis (SEM) (the force at break, the maximum elongation at break, tensile strength, and modulus of elasticity). Through SILP incorporation, the mechanical properties of composites, including the modulus of elasticity and tensile strength, are substantially improved, a phenomenon akin to traditional filler effects. The findings highlight SILP materials as prospective candidates for concurrent hardening and filling roles within composites (through a single-step procedure, with prolonged storage stability and controlled processing conditions), particularly pertinent as the composite industry veers toward epoxy bioresins necessitating liquefaction via temperature application.

Viability Study of Serra da Estrela Dog Wool to Produce Green Composites

The environmental emergency has alerted consumers and industries to choose products derived from renewable sources over petroleum derivatives. Natural fibers of plant origin for reinforcing composite materials dominate the field of research aiming to replace synthetic fibers. The field of application of green dog wool composite materials needs to be reinforced and proven, as the industry is looking for more sustainable solutions and on the other hand this type of raw material (pet grooming waste) tends to grow. Hence, in the present work, the feasibility of applying natural fibers of dog origin (mainly composed by keratin) in green composites was studied. The green composites were developed using chemically treated dog wool of the breed Serra da Estrela (with NaOH and PVA) as reinforcement and a green epoxy resin as a matrix. The chemical treatments aimed to improve adhesion between fibers and matrix. The fibers' composition was determined using X-ray Diffraction (X-RD). Their morphology was determined using a scanning electron microscope (SEM). The wettability of the fiber was also evaluated qualitatively by analyzing drops of resin placed on the fibers treated with the different treatments. The mechanical properties of the composites were also studied through mechanical tensile, flexural, and relaxation tests. Overall, the best results were obtained for the dog wool fibers without treatment. The tensile and flexural strength of this biocomposite were 11 MPa and 26.8 MPa, respectively, while the tensile and flexural elastic modulus were 555 MPa and 1100 MPa, respectively. It was also possible to verify that the PVA treatment caused degradation of the fiber, resulting in a decrease in mechanical tensile strength of approximately 42.7%, 59.7% in flexural strength and approximately 59% of the stress after 120 min of relaxation when compared to fiber made from untreated dog wool. On the other hand, the NaOH treatment worked as a fiber wash process, removing waxes and fats naturally present on the fiber surface.

Bio-based hyperbranched epoxy resins: synthesis and recycling

Epoxy resins (EPs), accounting for about 70% of the thermosetting resin market, have been recognized as the most widely used thermosetting resins in the world. Nowadays, 90% of the world's EPs are obtained from the bisphenol A (BPA)-based epoxide prepolymer. However, certain limitations severely impede further applications of this advanced material, such as limited fossil-based resources, skyrocketing oil prices, nondegradability, and a "seesaw" between toughness and strength. In recent years, more and more research has been devoted to the preparation of novel epoxy materials to overcome the compromise between toughness and strength and solve plastic waste problems. Among them, the development of bio-based hyperbranched epoxy resins (HERs) is unique and attractive. Bio-based HERs synthesized from bio-derived monomers can be used as a matrix resin or a toughener resulting in partially or fully bio-based epoxy thermosets. The introduction of a hyperbranched structure can balance the strength and toughness of epoxy thermosets. Here, we especially focused on the recent progress in the development of bio-based HERs, including the monomer design, synthesis approaches, mechanical properties, degradation, and recycling strategies. In addition, we advance the challenges and perspectives to engineering application of bio-based HERs in the future. Overall, this review presents an up-to-date overview of bio-based HERs and guidance for emerging research on the sustainable development of EPs in versatile high-tech fields.

Recent advancement in synthesizing bio-epoxy nanocomposites using lignin, plant oils, saccharides, polyphenols, and natural rubbers: A review

Due to environmental issues, production costs, and the low recycling capability of conventional epoxy polymers and their composites, many science groups have tried to develop a new type of epoxy polymers, which are compatible with the environment. Considering the precursors, these polymers can be produced from plant oils, saccharides, lignin, polyphenol, and natural resins. The appearance of these bio-polymers caused to introduce a new type of composites, namely bio-epoxy nanocomposites, which can be classified according to the synthesized bio-epoxy, the used nanomaterials, or both. Hence, in this work, various bio-epoxy resins, which have the proper potential for application as a matrix, are completely introduced with the synthesis viewpoint, and their characterized chemical structures are drawn. In the next steps, the bio-epoxy nanocomposites are classified based on the used nanomaterials, which are carbon nanoparticles (carbon nanotubes, graphene nanoplatelets, graphene oxide, reduced graphene oxide, etc.), nano-silica (mesoporous and spherical), cellulose (nanofibers and whiskers), nanoclay and so on. Also, the features of these bio-nanocomposites and their applications are introduced. This review study can be a proper guide for developing a new type of green nanocomposites in the near future.

Modification of Epoxides with Metallic Fillers-Mechanical Properties after Ageing in Aqueous Environments

The aim of this research was a comparative analysis of selected mechanical properties of epoxy compounds that were modified with metallic fillers and aged in aqueous environments. The tested epoxy compounds consisted of three components: styrene modified epoxy resin based on Bisphenol A, triethylenetetramine curing agent (resin/curing agent ratio of 100:10) and two types of metallic fillers in the form of particles: aluminum alloy (EN AW-2024-AlCu4Mg1) and tin-phosphor bronze (CuSn10P). Samples were subjected to ageing in 4 water environments: low-, medium- and high-mineralized natural water and in a sugar-containing solution for 1, 2 and 3 months. The epoxy samples were subjected to compressive strength tests in accordance with the ISO 604:2002 standard. It was observed that, among others, the compositions seasoned in low-mineralized water usually achieved the highest average compressive strength. As for filler type, using the bronze filler (CuSn10P) usually achieved the highest average compressive strength results.

Re-Assemblable, Recyclable, and Self-Healing Epoxy Resin Adhesive Based on Dynamic Boronic Esters

Thermosetting adhesives are commonly utilized in various applications. However, covalent cross-linked networks prevent thermosetting adhesives from being re-assembled, which necessitates higher machining precision. Additionally, the primary raw materials used in adhesive preparation are derived from non-renewable petroleum resources, which further constrain adhesive development. In this study, a recyclable adhesive was developed by incorporating dynamic boronic esters into epoxy resin derived from soybean oil. The successful synthesis of epoxidized soybean oil and boronic esters was confirmed through the analysis of proton nuclear magnetic resonance spectra and differential scanning calorimetry results. Swelling tests and tensile curves demonstrated the presence of covalently cross-linked networks. Self-healing and reprocessing experiments indicated that the cross-linked network topology could be re-assembled under mild conditions.

Benchmark Study of Epoxy Coatings with Selection of Bio-Based Phenalkamine versus Fossil-Based Amine Crosslinkers

The phenalkamines (PK) derived from cardanol oil can be used as a bio-based crosslinker for epoxy coatings as an alternative for traditional fossil amines (FA). First, the reaction kinetics of an epoxy resin with four PK and FA crosslinkers are compared by differential scanning calorimetry, illustrating a fast reaction rate and higher conversion of PK at room temperature in parallel with a moderate exothermal reaction. Second, the performance of coatings with various concentrations of PK and PK/FA ratios indicates good mixing compatibility between crosslinkers resulting in higher hardness, scratch resistance, hydrophobicity, and abrasive wear resistance of coatings with PK. The superior performance is confirmed over a broad range of resin/crosslinker ratios, facilitating the processing with viscosity profiles depending on the PK type. Although fossil- and bio-based crosslinkers have different chemical structures, the unique linear relationships between intrinsic mechanical properties (i.e., ductility and impact resistance) and coating performance indicate that the degree of crosslinking is a primary parameter controlling coating performance, where PK simultaneously provides high hardness and ductility. In conclusion, the optimization of the processing range for bio-based PK as a crosslinker for epoxy coatings delivers suitable processing conditions and superior mechanical performance compared to traditional amine crosslinkers.

Influence of Biochar and Bio-Oil Loading on the Properties of Epoxy Resin Composites

In this study, we evaluated the use of bio-oil and biochar on epoxy resin. Bio-oil and biochar were obtained from the pyrolysis of wheat straw and hazelnut hull biomass. A range of bio-oil and biochar proportions on the epoxy resin properties and the effect of their substitution were investigated. TGA curves showed improved thermal stability for degradation temperature at the 5% (T5%), 10% (T10%), and 50% (T50%) weight losses on bioepoxy blends with the incorporation of bio-oil and biochar with respect to neat resin. However, decreases in the maximum mass loss rate temperature (T_max) and the onset of thermal degradation (T_onset) were obtained. Raman characterization showed that the degree of reticulation with the addition of bio-oil and biochar does not significantly affect chemical curing. The mechanical properties were improved when bio-oil and biochar were incorporated into the epoxy resin. All bio-based epoxy blends showed a large increase in Young's modulus and tensile strength with respect to neat resin. Young's modulus was approximately 1955.90 to 3982.05 MPa, and the tensile strength was between 8.73 and 13.58 MPa for bio-based blends of wheat straw. Instead, in bio-based blends of hazelnut hulls, Young´s modulus was 3060.02 to 3957.84 MPa, and tensile strength was 4.11 to 18.11 Mpa.

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.

Application of an Eco-Friendly Adhesive and Electrochemical Nanostructuring for Joining of Aluminum A1050 Plates

In adhesive joints used in several industrial applications, the adherends' bonding is made using an adhesive, which is usually an epoxy resin. However, since these adhesives are derived from petroleum fractions, they are harmful to the environment, due to the pollutants produced both during their manufacture and subsequent use. Thus, in recent years, effective steps have been made to replace these adhesives with ecological (green) ones. The present work focuses on the study of aluminum A1050 joints bonded with a green adhesive; the study also involves the electrochemical anodization method applied to adherends for nano-functionalization. The nanostructured aluminum adherends allow the formation of an expanded surface area for adhesion, compared to the non-anodized adherends. For comparison reasons, two different adhesives (Araldite LY1564 and Green Super Sap) were used. In addition, for the same reasons, both anodized and non-anodized aluminum adherends were joined with both types of adhesives. The lap joints were subsequently tested under both shear-tension and three-point bending conditions. The major findings were that aluminum A1050 anodization in all cases resulted in shear strength enhancement of the joints, while joints with both aluminum anodized and non-anodized adherends and bonded with the eco-friendly adhesive showed a superior shear behavior as compared to the respective joints bonded with Araldite adhesive.

Epoxidized and Maleinized Hemp Oil to Develop Fully Bio-Based Epoxy Resin Based on Anhydride Hardeners

The present work aims to develop thermosetting resins using epoxidized hemp oil (EHO) as a bio-based epoxy matrix and a mixture of methyl nadic anhydride (MNA) and maleinized hemp oil (MHO) in different ratios as hardeners. The results show that the mixture with only MNA as a hardener is characterized by high stiffness and brittleness. In addition, this material is characterized by a high curing time of around 170 min. On the other hand, as the MHO content in the resin increases, the mechanical strength properties decrease and the ductile properties increase. Therefore, it can be stated that the presence of MHO confers flexible properties to the mixtures. In this case, it was determined that the thermosetting resin with balanced properties and high bio-based content contains 25% MHO and 75% MNA. Specifically, this mixture obtained a 180% higher impact energy absorption and a 195% lower Young’s modulus than the sample with 100% MNA. Also, it has been observed that this mixture has significantly shorter times than the mixture containing 100% MNA (around 78 min), which is of great concern at an industrial level. Therefore, thermosetting resins with different mechanical and thermal properties can be obtained by varying the MHO and MNA content.

l-Lysine Stabilized FeNi Nanoparticles for the Catalytic Reduction of Biomass-Derived Substrates in Water Using Magnetic Induction

The reduction of biomass-derived compounds gives access to valuable chemicals from renewable sources, circumventing the use of fossil feedstocks. Herein, we describe the use of iron-nickel magnetic nanoparticles for the reduction of biomass model compounds in aqueous media under magnetic induction. Nanoparticles with a hydrophobic ligand (FeNi₃ -PA, PA=palmitic acid) have been employed successfully, and their catalytic performance is intended to improve by ligand exchange with lysine (FeNi₃ -Lys and FeNi₃ @Ni-Lys NPs) to enhance water dispersibility. All three catalysts have been used to hydrogenate 5-hydroxymethylfurfural into 2,5-bis(hydroxymethyl)furan with complete selectivity and almost quantitative yields, using 3 bar of H₂ and a magnetic field of 65 mT in water. These catalysts have been recycled up to 10 times maintaining high conversions. Under the same conditions, levulinic acid has been hydrogenated to γ-valerolactone, and 4'-hydroxyacetophenone hydrodeoxygenated to 4-ethylphenol, with conversions up to 70 % using FeNi₃ -Lys, and selectivities above 85 % in both cases. This promising catalytic system improves biomass reduction sustainability by avoiding noble metals and expensive ligands, increasing energy efficiency via magnetic induction heating, using low H₂ pressure, and proving good reusability while working in an aqueous medium.

Techno-economic and environmental sustainability analysis of filament-winding versus pultrusion based glass-fiber composite technologies

In the era of sustainable development, glass-fiber reinforced polymer (GFRP) composites have made their way into modern engineering, construction, and building sectors due to their exponential characteristics. While considering the rapid growth and development in this sector, this research has assessed the relative environmental and techno-economic sustainability of two sorts of GFRP composite technologies: (a) filament winding and (b) pultrusion to effectively appraise their application, merits, and demerits. This study will help low-middle-income countries like Pakistan toward cleaner production, environmental management, and sustainable industrial development. The techno-economic sustainability is determined by using life cycle costing and techno-economic indicators, i.e., benefit-cost (B/C) ratio, net present value (NVP), internal rate of return (IRR), and payback period. The B/C ratio depicts the relationship between the relative cost and benefits of a technology, and NVP expresses the calculated present value of the future payback stream of a technological investment, while the IRR is an effective techno-economic indicators which can predict the efficacy of an investment, and the payback period is the time forecast for a technology to recover its investments. These techno-economic analytics showed that the net life-cycle cost performance, B/C ratio, and IRR are 5%, 7%, and 15% higher respectively for filament winding-based GFRP technology than the pultrusion-based manufacturing technology, whereas overall net life cycle benefits are about 80% greater for filament winding. Similarly, the payback time is shorter for filament winding compared to pultrusion. The environmental sustainability is determined, by employing a relative life cycle analysis (LCA) for both technologies. The system boundary for the study is "gate to gate," i.e., manufacturing phase, where these technologies are assessed for their environmental externalities. The functional unit of "1 kg finished product," i.e., manufactured by pultrusion and filament winding technology, and eight life cycle impact assessment (LCIA) categories; climate change potential (CCP), terrestrial eco-toxicity potential (TETP), ozone depletion potential (ODP), fossil resource depletion potential (FDP), acidification potential (AP), eutrophication potential (EP), particulate matter (PM) formation, and water consumption potential (WCP) have been selected. The significant ecological impact scores are determined in the categories of CCP (kg CO₂ eq.) as 10.8E + 00 and 5.01E + 00 and ETP (kg. 2,4-D eq.) as 1.26E-02 and 9.47E-03 and FDP (kg Oil eq.) as 3.96E + 00 and 2.59E + 00 for filament winding and pultrusion-based GFRP technologies, respectively. These LCIA results depicted that the ecological performance of filament winding technology is specifically better than pultrusion technology in the categories of EP, PM, and WCP, while, for all other life cycle impact categories, the pultrusion technology has depicted significantly lower impact potential and is environmentally more sustainable. The outcomes of this research will be greatly assistive for researchers, developers, manufacturers, and policymakers to effectively appraise the externalities and selection of a more sustainable GFRP technology.

Preparation Optimization of CFRP and EPDM Composite by the Co-Curing Method

As the requirements of aerospace technology become more rigorous, the performance of solid rocket motor (SRM) cases needs to be further optimized. In the present study, a co-curing technique was used to fabricate carbon fiber reinforced polymer (CFRP)/ethylene-propylene-diene monomer (EPDM) composites whereby the properties of CFRP/EPDM composites were adjusted by varying the temperature, heating time and type of vulcanizing agent to obtain the optimum manufacturing process. The results of crosslink density (3.459 × 10^-4 mol/cm³) tested by nuclear magnetic resonance (NMR), a 90° peel strength test (2.342 N/mm), and an interlaminar shear test (ILSS = 82.08 MPa) demonstrated that the optimum mechanical properties of composites were obtained under the temperature 160 °C heated for 20 min with the curing agent DCP/S. The interfacial phase and bonding mechanism of composites were investigated by scanning electron microscopy (SEM). Thermogravimetric analysis (TGA) further indicated that EPDM/DCP/S had favorable thermal stability. This will provide valuable recommendations for the optimization of the SRM shell preparation process.

A Critical Review of Sustainable Vanillin-modified Vitrimers: Synthesis, Challenge and Prospects

Nearly 90% of thermosets are produced from petroleum resources, they have remarkable mechanical characteristics, are chemically durable, and dimensionally stable. However, they can contribute to global warming, depletion of petroleum reserves, and environmental contamination during manufacture, use, and disposal. Using renewable resources to form thermosetting materials is one of the most crucial aspects of addressing the aforementioned issues. Vanillin-based raw materials have been used in the industrial manufacturing of polymer materials because they are simple to modify structurally. Conversely, traditional thermosetting materials as a broad class of high-molecular-weight molecules are challenging to heal, decompose and recover owing to their permanent 3-D crosslinking network. Once the products are damaged, recycling issues could arise, causing resource loss and environmental impact. It could be solved by inserting dynamic covalent adaptable networks (DCANs) into the polymer chains, increasing product longevity, and minimizing waste. It also improves the attractiveness of these products in the prospective field. Moreover, it is essential to underline that increasing product lifespan and reducing waste is equivalent to reducing the expense of consuming resources. The detailed synthesis, reprocessing, thermal, and mechanical characteristics of partly and entirely biomass thermosetting polymers made from vanillin-modified monomers are covered in the current work. Finally, the review highlights the benefits, difficulties, and application of these emerging vanillin-modified vitrimers as a potential replacement for conventional non-recyclable thermosets.

A Diamine-Oriented Biorefinery Concept Using Ammonia and Raney Ni as a Multifaceted Catalyst

Diamines are important industrial chemicals. In this paper we outline the feasibility of lignocellulose as a source of diol-containing molecules. We also illustrate the possibility of turning these diols into their diamines in good to excellent yields. Central to these transformations is the use of commercially available Raney Ni. For diol formation, the Raney Ni engages in hydrogenation and often also demethoxylation, that way funneling multiple components to one single molecule. For diamine formation, Raney Ni catalyzes hydrogen-borrowing mediated diamination in the presence of NH₃.

Characterization of Biocomposites and Glass Fiber Epoxy Composites Based on Acoustic Emission Signals, Deep Feature Extraction, and Machine Learning

This study presents the results of acoustic emission (AE) measurements and characterization in the loading of biocomposites at room and low temperatures that can be observed in the aviation industry. The fiber optic sensors (FOS) that can outperform electrical sensors in challenging operational environments were used. Standard features were extracted from AE measurements, and a convolutional autoencoder (CAE) was applied to extract deep features from AE signals. Different machine learning methods including discriminant analysis (DA), neural networks (NN), and extreme learning machines (ELM) were used for the construction of classifiers. The analysis is focused on the classification of extracted AE features to classify the source material, to evaluate the predictive importance of extracted features, and to evaluate the ability of used FOS for the evaluation of material behavior under challenging low-temperature environments. The results show the robustness of different CAE configurations for deep feature extraction. The combination of classic and deep features always significantly improves classification accuracy. The best classification accuracy (80.9%) was achieved with a neural network model and generally, more complex nonlinear models (NN, ELM) outperform simple models (DA). In all the considered models, the selected combined features always contain both classic and deep features.

Network Formation and Physical Properties of Epoxy Resins for Future Practical Applications

Epoxy resins are used in various fields in a wide range of applications such as coatings, adhesives, modeling compounds, impregnation materials, high-performance composites, insulating materials, and encapsulating and packaging materials for electronic devices. To achieve the desired properties, it is necessary to obtain a better understanding of how the network formation and physical state change involved in the curing reaction affect the resultant network architecture and physical properties. However, this is not necessarily easy because of their infusibility at higher temperatures and insolubility in organic solvents. In this paper, we summarize the knowledge related to these issues which has been gathered using various experimental techniques in conjunction with molecular dynamics simulations. This should provide useful ideas for researchers who aim to design and construct various thermosetting polymer systems including currently popular materials such as vitrimers over epoxy resins.

Closing the Carbon Loop in the Circular Plastics Economy

Today, plastics are ubiquitous in everyday life, problem solvers of modern technologies, and crucial for sustainable development. Yet the surge in global demand for plastics of the growing world population has triggered a tidal wave of plastic debris in the environment. Moving from a linear to a zero-waste and carbon-neutral circular plastic economy is vital for the future of the planet. Taming the plastic waste flood requires closing the carbon loop through plastic reuse, mechanical and molecular recycling, carbon capture, and use of the greenhouse gas carbon dioxide. In the quest for eco-friendly products, plastics do not need to be reinvented but tuned for reuse and recycling. Their full potential must be exploited regarding energy, resource, and eco efficiency, waste prevention, circular economy, climate change mitigation, and lowering environmental pollution. Biodegradation holds promise for composting and bio-feedstock recovery, but it is neither the Holy Grail of circular plastics economy nor a panacea for plastic littering. As an alternative to mechanical downcycling, molecular recycling enables both closed-loop recovery of virgin plastics and open-loop valorization, producing hydrogen, fuels, refinery feeds, lubricants, chemicals, and carbonaceous materials. Closing the carbon loop does not create a Perpetuum Mobile and requires renewable energy to achieve sustainability. This article is protected by copyright. All rights reserved.

Cardanol-Derived Epoxy Resins as Biobased Gel Polymer Electrolytes for Potassium-Ion Conduction

In this study, biobased gel polymer electrolyte (GPE) membranes were developed via the esterification reaction of a cardanol-based epoxy resin with glutaric anhydride, succinic anhydride, and hexahydro-4-methylphthalic anhydride. Nonisothermal differential scanning calorimetry was used to assess the optimal curing time and temperature of the formulations, evidencing a process activation energy of ∼65-70 kJ mol-1. A rubbery plateau modulus of 0.65-0.78 MPa and a crosslinking density of 2 × 10-4 mol cm-3 were found through dynamic mechanical analysis. Based on these characteristics, such biobased membranes were tested for applicability as GPEs for potassium-ion batteries (KIBs), showing an excellent electrochemical stability toward potassium metal in the -0.2-5 V voltage range and suitable ionic conductivity (10-3 S cm-1) at room temperature. This study demonstrates the practical viability of these biobased materials as efficient GPEs for the fabrication of KIBs, paving the path to increased sustainability in the field of next-generation battery technologies.

Hemp fibers modified with graphite oxide as green and efficient solution for water remediation: Application to methylene blue

In this paper, the use of hemp fibers modified with graphite oxide for the removal of methylene blue (MB) from aqueous solutions was investigated. Parameters such as contact time, pH, temperature, initial concentration of dye and ionic strength were varied and their effects on the adsorption recovery were evaluated. The adsorption process attained the equilibrium within 30 min while the adsorption capacity was found to increase with increasing contact time. The experimental data were fitted through a pseudo-second order model. Maximum adsorption capacity slightly increases with temperature changing from 54 mg/g to 58 mg/g at pH = 7.5, from 37 mg/g to 45 mg/g at pH = 3 and from 44 mg/g to 49 mg/g at pH = 12, by increasing the temperature from 20 °C to 80 °C indicating that the process is slightly endothermic (ΔH = 3.43 kJ/mol). The thermodynamic parameters were even calculated demonstrating that the process is spontaneous (ΔG ≈ -4.4 J/mol K and ΔS = 3.16 J/mol K)). Finally, a mathematical algorithm was applied to forecast the response surface model. A second order model was chosen to fit the experimental data and the statistical effect of the process parameters were estimated. A numerical optimization was even performed to individuate the optimal set of process parameters (pH = 9.25, T = 53.8 °C and C₀ = 13.2 mg/L) which maximizes the removal capacity. A possible adsorption mechanism was even presented. So, it was proved the efficiency of the adsorption of a novel, inexpensive and sustainable composite material obtained from agro-waste resources by performing reusability cycles.

Βio-Based Epoxy/Amine Reinforced with Reduced Graphene Oxide (rGO) or GLYMO-rGO: Study of Curing Kinetics, Mechanical Properties, Lamination and Bonding Performance

In this work, we report the synthesis and study of nanocomposites with a biobased epoxy/amine (Epilok 60-600G/Curamine 30-952) matrix reinforced with reduced graphene oxide (rGO) or functionalised with 3-glycidoxypropyltrimethoxysilane (GLYMO-rGO). These graphene related materials (GRMs) were first dispersed into a Curamine hardener using bath ultrasonication, followed by the addition of epoxy resin. Curing kinetics were studied by DSC under non-isothermal and isothermal conditions. The addition of 1.5 wt% of GLYMO-rGO into the epoxy matrix was found to increase the degree of cure by up to 12% and glass transition temperature by 14 °C. Mechanical testing showed that the addition of 0.05 wt% GLYMO-rGO improves Young's modulus and tensile strength by 60% and 16%, respectively, compared to neat epoxy. Carbon fibre reinforced polymer (CFRP) laminates were prepared via hand lay up, using the nanocomposite system GRM/Epilok/Curamine as matrix, and were cut as CFRP adherents for lap shear joints. GRM/Epilok/Curamine was also used as adhesive to bond CFRP/CFRP and CFRP/aluminium adherents. The addition of 0.1 wt% GLYMO-rGO into the adhesive and CRFP adherents showed improved lap shear strength by 23.6% compared to neat resin, while in the case of CFRP/Aluminium joints the increase was 21.2%.

A comparison of adhesive polysulfides initiated by garlic essential oil and elemental sulfur to create recyclable adhesives

Sulfur and garlic essential oil can initiate polymerization with a variety of natural monomers to form sustainable adhesives. The sulfur source has a substantial impact on the adhesion strength and material properties.

Synthesis of non-phosphorylated epoxidised corn oil as a novel green flame retardant thermoset resin

This study aimed to produce a new potential flame retardant thermoset resin from epoxidised corn oil through a one-pot method using liquid inorganic catalysed with hydrogen peroxide. Using a gas chromatography-mass selective detector, attenuated total reflectance-fourier transform infrared spectroscopy, proton nuclear magnetic resonance imaging, optical microscopy, and scanning emission microscopy, we synthesised a bio-based resin based on newly designed parameters. The flame retardant capacity was fully established using thermogravimetric analysis and a micro calorimeter. The produced epoxidised corn oil had a relative percentage conversion of oxirane of approximately 91.70%, wherein the amount of double bonds converted into epoxides was calculated. A significant reduction from 17 to 40% in peak heat rate release (pHRR) and 26-30% in total heat release was observed, confirming its flame retardant property. Thus, the potential of epoxidised corn oil was demonstrated.

Bio-Based Epoxy Adhesives with Lignin-Based Aromatic Monophenols Replacing Bisphenol A

A bio-epoxy surface adhesive for adherence of the metal component species to glass substrate with desirable adhesion strength, converted controlled removal upon request, and bio-based resource inclusion was developed. For the development of resin, three different lignin-based aromatic monophenols, guaiacol, cresol, and vanillin, were used in the chemical epoxidation reaction with epichlorohydrin. The forming transformation process was studied by viscoelasticity, in situ FTIR monitoring, and Raman. Unlike other hydroxyl phenyls, guaiacol showed successful epoxide production, and stability at room temperature. Optimization of epoxide synthesis was conducted by varying NaOH concentration or reaction time. The obtained product was characterized by nuclear magnetic resonance and viscosity measurements. For the production of adhesive, environmentally problematic bisphenol A (BPA) epoxy was partially substituted with the environmentally acceptable, optimized guaiacol-based epoxy at 20, 50, and 80 wt.%. Mechanics, rheological properties, and the possibility of adhered phase de-application were assessed on the bio-substitutes and compared to commercially available polyepoxides or polyurethanes. Considering our aim, the sample composed of 80 wt.% bio-based epoxy/20 wt.% BPA thermoset was demonstrated to be the most suitable among those analyzed, as it was characterized by low BPA, desired boundary area and recoverability using a 10 wt.% acetic acid solution under ultrasound.

Curing Behavior and Thermomechanical Performance of Bioepoxy Resin Synthesized from Vanillyl Alcohol: Effects of the Curing Agent

In order to reduce the dependency of resin synthesis on petroleum resources, vanillyl alcohol which is a renewable material that can be produced from lignin has been used to synthesize bioepoxy resin. Although it has been widely reported that the curing reaction and properties of the cured epoxies can be greatly affected by the molecular structure of the curing agents, the exact influence remains unknown for bioepoxies. In this study, four aliphatic amines with different molecular structures and amine functionalities, namely triethylenetetramine (TETA), Tris(2-aminoethyl)amine (TREN), diethylenetriamine (DETA), and ethylenediamine (EDA), were used to cure the synthesized vanillyl alcohol-based bioepoxy resin (VE). The curing reaction of VE and the physicochemical properties, especially the thermomechanical performance of the cured bioepoxies with different amine functionalities, were systematically investigated and compared using different characterization methods, such as DSC, ATR-FTIR, TGA, DMA, and tensile testing, etc. Despite a higher curing temperature needed in the VE-TETA resin system, the cured VE-TETA epoxy showed a better chemical resistance, particularly acidic resistance, as well as a lower swelling ratio than the others. The higher thermal decomposition temperature, storage modulus, and relaxation temperature of VE-TETA epoxy indicated its superior thermal stability and thermomechanical properties. Moreover, the tensile strength of VE cured by TETA was 1.4~2.6 times higher than those of other curing systems. In conclusion, TETA was shown to be the optimum epoxy curing agent for vanillyl alcohol-based bioepoxy resin.

Lanthanide dodecyl sulfates, a potent family of catalysts for the preparation of biobased epoxy thermosets

Lanthanide dodecyl sulfates, LnDS_x, are remarkably effective to catalyze the reaction of diepoxides with diamines in the liquid and solid states, a key reaction in the formation of epoxy thermosets. Among all lanthanides, the lanthanum complex LaNa(DS)₄(H₂O)₂ is the most active, allowing a decrease of 60 kJ mol^-1 of the activation energy between polyethylene imine and limonene dioxide, a biobased epoxy monomer.

Composition and Properties of Protective Coatings Made of Biologically-Derived Polyester Reactive Binder

Biologically derived polymers are a very attractive subject for investigation, due to the strict pro-ecological requirements imposed by developed countries, including zero-waste and zero-carbon policies as well as volatile organic compound (VOC) limits. Synthesis of biologically-derived polyesters from natural rosin and bio-diols, showing softening temperatures suitable for application in VOC-free paints and varnishes, was performed to create a desired, future commercial product, that meet the aforementioned requirements regarding VOC and elimination of petroleum-based raw materials. Prepared polymers were used in the formulation of coating materials whose properties: cross-linking behavior, glass transition temperature, thermal stability, storage modulus, hardness, cupping resistance, adhesion, chemical resistance, gloss, haze, color, and anti-corrosive behavior in the salt chamber were investigated and discussed. As a result, coatings with prepared bio-polyesters contained over 80 wt.% of natural resources and showed competitive/better properties than petroleum-based references. They can be applied in the prototyping of “green” powder paints for the protection of steel substrates from corrosion and aggressive solvents.