In-Situ Epoxidation of Waste Cooking Oil and Its Methyl Esters for Lubricant Applications: Characterization and Rheology

Multifunctional 3D-Printable Photocurable Elastomer with Self-Healing Capability Derived from Waste Cooking Oil

This study presents a sustainable approach to transform waste cooking oil (WCO) into a multifunctional 3D-printable photocurable elastomer with integrated self-healing capabilities. A linear monomer, WCO-based methacrylate fatty acid ethyl ester (WMFAEE), was synthesized via a sequential strategy of transesterification, epoxidation, and ring-opening esterification. By copolymerizing WMFAEE with hydroxypropyl acrylate (HPA), a novel photocurable elastomer was developed, which could be amenable to molding using an LCD light-curing 3D printer. The resulting WMFAEE-HPA elastomer exhibits exceptional mechanical flexibility (elongation at break: 645.09%) and autonomous room-temperature self-healing properties, achieving 57.82% recovery of elongation after 24 h at 25 °C. Furthermore, the material demonstrates weldability (19.97% retained elongation after 12 h at 80 °C) and physical reprocessability (7.75% elongation retention after initial reprocessing). Additional functionalities include pressure-sensitive adhesion (interfacial toughness: 70.06 J/m2 on glass), thermally triggered shape memory behavior (fixed at -25 °C with reversible deformation/recovery at ambient conditions), and notable biodegradability (13.25% mass loss after 45-day soil burial). Molecular simulations reveal that the unique structure of the WMFAEE monomer enables a dual mechanism of autonomous self-healing at room temperature without external stimuli: chain diffusion and entanglement-driven gap closure, followed by hydrogen bond-mediated network reorganization. Furthermore, the synergy between monomer chain diffusion/entanglement and dynamic hydrogen bond reorganization allows the WMFAEE-HPA system to achieve a balance of multifunctional integration. Moreover, the integration of these multifunctional attributes highlights the potential of this WCO-derived photocurable elastomer for various possible 3D printing applications, such as flexible electronics, adaptive robotics, environmentally benign adhesives, and so on. It also establishes a paradigm for converting low-cost biowastes into high-performance smart materials through precision molecular engineering.

Biolubricants from waste cooking oil: A review of extraction technologies, conversion techniques, and performance enhancement using natural antioxidants

Effective management of agricultural and industrial by-products is essential for promoting circular economic practices and enhancing environmental sustainability. Agri-food wastes and waste cooking oil (WCO) represent two abundant residual streams with significant potential for sustainable biolubricant production. Valorizing biomass and WCO aligns with Sustainable Development Goal (SDG) 7, as it improves energy efficiency through enhanced lubricant performance and reduced energy loss. Furthermore, this sustainable approach contributes to SDG 12 and SDG 13 by minimizing waste production and accumulation, thereby mitigating negative environmental impacts and climate change. This critical review addresses existing gaps in the production of biolubricants from WCO and the incorporation of natural antioxidants as versatile additives. It examines and compares various techniques for the extraction, chemical and physical modification, and characterization of WCO-derived biolubricants. Specific methods, including esterification, transesterification, and antioxidant incorporation, are evaluated for their effectiveness in converting WCO into biolubricants. The review also discusses the influence of residual bioactive compounds on oxidative stability and lubricating properties. While vegetable oils demonstrate superior friction-reducing capabilities compared to petroleum-based lubricants, their triglyceride structure often results in poor oxidative stability, limiting their practical applications. Modification strategies and antioxidant inclusion are proposed to enhance this stability. A comprehensive analysis of the physicochemical properties and tribological performance of biolubricants, both pre- and post-processing, is presented. This systematic evaluation of extraction and upgrading methodologies aims to facilitate the development and industrial adoption of sustainable biolubricants.

A 4D-Printable Photocurable Resin Derived from Waste Cooking Oil with Enhanced Tensile Strength

In pursuit of enhancing the mechanical properties, especially the tensile strength, of 4D-printable consumables derived from waste cooking oil (WCO), we initiated the production of acrylate-modified WCO, which encompasses epoxy waste oil methacrylate (EWOMA) and epoxy waste oil acrylate (EWOA). Subsequently, a series of WCO-based 4D-printable photocurable resins were obtained by introducing a suitable diacrylate molecule as the second monomer, coupled with a composite photoinitiator system comprising Irgacure 819 and p-dimethylaminobenzaldehyde (DMAB). These materials were amenable to molding using an LCD light-curing 3D printer. Our findings underscored the pivotal role of triethylene glycol dimethacrylate (TEGDMA) among the array of diacrylate molecules in enhancing the mechanical properties of WCO-based 4D-printable resins. Notably, the 4D-printable material, composed of EWOA and TEGDMA in an equal mass ratio, exhibited nice mechanical strength comparable to that of mainstream petroleum-based 4D-printable materials, boasting a tensile strength of 9.17 MPa and an elongation at break of 15.39%. These figures significantly outperformed the mechanical characteristics of pure EWOA or TEGDMA resins. Furthermore, the EWOA-TEGDMA resin demonstrated impressive thermally induced shape memory performance, enabling deformation and recovery at room temperature and retaining its shape at -60 °C. This resin also demonstrated favorable biodegradability, with an 8.34% weight loss after 45 days of soil degradation. As a result, this 4D-printable photocurable resin derived from WCO holds immense potential for the creation of a wide spectrum of high-performance intelligent devices, brackets, mold, folding structures, and personalized products.

Effects of direct sulfonation on the catalytic activity and recyclability of novel lignin-based solid acid catalysts from agri-food waste

Catalytic systems derived from lignin are emerging as quite efficient and profitable materials in many catalyzed transformations. However, these catalysts have been predominantly synthesized by carbonization. Alternatively, we prepared direct sulfonation lignin (DSL) and compared it to the carbonized-sulfonated lignin (CSL) catalyst, aiming to reveal the effects of direct functionalization of lignin on its catalytic performance and to simplify its preparation. Both catalysts were well characterized by several physicochemical techniques, and their catalytic activities were assessed by catalyzed esterification. Using CSL, the yield reached 94.11 % under the optimal conditions (60 °C, 4 h and 50 mg loading), while DSL yielded 93.97 % with only 2 h under the same conditions, which is attributed to the abundant catalytic active sites in DSL (0.62 mmol/g of SO₃H against 0.39 mmol/g for CSL). Furthermore, the activation energies were found to be 21 and 16 kJ mol^-1 for CSL and DSL, respectively, suggesting that esterification can occur with less energy input using DSL. Reusability showed that leaching of SO₃H groups and mass loss are inherently responsible for deactivation. However, both lignin-based catalysts show good stability and can be reused for 4 successive cycles. Direct lignin functionalization can be an alternative to conventional catalyst processing.

Fatty acid wax from epoxidation and hydrolysis treatments of waste cooking oil: synthesis and properties

To provide low-cost wax and a new methodology for utilizing waste cooking oil (WCO), fatty acid wax based on WCO was synthesized by using epoxidation and hydrolysis treatments, whose properties included melting point, color, hardness, combustion properties, aldehyde content, and microscopic morphology were tested and analyzed. The obtained WCO-based wax contained mixed fatty acids, including palmitic acid and 9,10-dihydroxystearic acid as main constituents, which could form a 3D stable crossing network constructed by large long-rod crystals. The WCO-based wax with high fatty acid content (96.41 wt%) has a high melting point (44-53 °C), light color (Lovibond color code Y = 11.9, R = 2.3), good hardness (needle penetration index = 2.66 mm), long candle burning time (293 min), and low aldehyde content (7.98 × 10^-2 μg g^-1), which could be a lower-cost alternative of commercial soybean wax (SW) for producing various wax products including candles, crayons, waxworks, etc.

The Twelve Principles of Green Tribology: Studies, Research, and Case Studies—A Brief Anthology

Sustainability has become of paramount importance, as evidenced by the increasing number of norms and regulations concerning various sectors. Due to its intrinsic trans-sectorial nature, tribology has drawn the attention of the supporters of sustainability. This discipline allows the environmental, economic, and social impacts to be decreased in a wide range of applications following the same strategies. In 2010, Nosonovsky and Bhushan drew up 12 approaches based on the 12 principles of green chemistry and the 12 principles of green engineering, defining the “12 principles of green tribology.” This review exploits the 12 principles of green tribology to fathom the developed research related to sustainability and tribology. Different approaches and innovative studies have been proposed in this short selection as references to consider for further development, pursuing the efforts of the scientific community for a sustainable future through the contribution also of tribosystems. The manuscript aims to provide practical examples of materials, lubricants, strategies, and technologies that have contributed to the overall progress of tribology, decreasing wear and friction and increasing efficiency, and at the same time promoting sustainable development, lowering toxicity, waste production, and loss of energy and resources.

Characterization, kinetics and thermodynamics of epoxidation-esterification of Irvingia gabonensis kernel oil methyl ester

Epoxidation-esterification of fatty acid methyl ester obtained from Irvingia gabonensis kernel oil (IGKO), as well as its characterization, kinetics and thermodynamics were the main focus of this study. The methyl ester obtained via base catalyzed transesterification was used for epoxidation-esterification modification process. Epoxidation kinetics and thermodynamics parameters were also investigated. The properties of the IGKO and epoxidized-esterified Irvingia gabonensis kernel oil (IGKO) methyl ester (MIGKO^e) were determined using standard methods. Rate constant K and activation energy Ea for the epoxidation process was found to be of the order 10−5 Lmol⁻¹s⁻¹ and 46.02 kJ/mol, respectively. ΔG, ΔH, and ΔS values for the epoxidation process were (94.74–101.42 kJ mol⁻¹), 43.30 kJ mol⁻¹, and – 167.20 J mol⁻¹ K⁻¹, respectively, indicating the non-spontaneous, endothermic, and endergonic nature of the process. The physicochemical characteristics of MIGKO^e were: 9 °C, 298 °C, 840 kg/dm³, 13.84 mm²/s, 1.351 mg KOH/g oil, 1.01 mg/kg and 39.78 kV, for pour point, flash point, density, viscosity, acid value, moisture content and dielectric strength, respectively. The MIGKO^e properties indicated its potential for use as a bio-transformer fluid, upon further treatment with pour point depressant.

Natural Antioxidant Extracted Waste Cooking Oil as Sustainable Biolubricant Formulation in Tribological and Rheological Applications

Developing eco-friendly formulations using waste cooking oil as renewable biomass is of great interest and commercial importance in the fuels and lubricant industry. This manuscript reports novel study on preparing a biolubricant formulations as WCO-1, WCO-2 and WCO-3 by blending the curcumin extracted soybean waste cooking oil in three different compositions viz 10%, 20%, 30% v/v with the mineral base oil N-150. Curcumin was extracted as a natural antioxidant in 0.5 wt% waste cooking oil to inhibit thermal oxidation. This study comprises a detailed analysis in terms of tribological, rheological and thermophysical characteristics such as viscosity, viscosity index, pour point and flash point parameters of the biolubricant by standard ASTM methods. Further, tribological and rheological analysis was done by the four-ball wear tester and Anton Paar, MCR-72, respectively. The thermophysical evaluation of WCO formulated biolubricant has shown excellent properties. The viscosity index of the formulated biolubricant increases with an increase in the concentration of waste cooking oil. In contrast, the pour point has also been depressing at lower temperature conditions. Thus, WCO based biolubricant was found to be more effective at extreme temperature conditions than the mineral base oil (N-150). Rheological studies have indicated the non-Newtonian behaviour of the biolubricant with an increase in shear rate. Whereas, tribological analysis demonstrates that wear scar diameter has significantly reduced from 0.685 to 0.573 mm, and the coefficient of friction decreased from 0.117 to 0.080 with respect to the mineral base oil. Thus, a straightforward green approach has been discovered by directly utilizing waste cooking oil for biolubricant formulation.

Potential of the Red Alga Dixoniella grisea for the Production of Additives for Lubricants

There is an increasing interest in algae-based raw materials for medical, cosmetic or nutraceutical applications. Additionally, the high diversity of physicochemical properties of the different algal metabolites proposes these substances from microalgae as possible additives in the chemical industry. Among the wide range of natural products from red microalgae, research has mainly focused on extracellular polymers for additive use, while this study also considers the cellular components. The aim of the present study is to analytically characterize the extra- and intracellular molecular composition from the red microalga Dixoniella grisea and to evaluate its potential for being used in the tribological industry. D. grisea samples, fractionated into extracellular polymers (EPS), cells and medium, were examined for their molecular composition. This alga produces a highly viscous polymer, mainly composed of polysaccharides and proteins, being secreted into the culture medium. The EPS and biomass significantly differed in their molecular composition, indicating that they might be used for different bio-additive products. We also show that polysaccharides and proteins were the major chemical compounds in EPS, whereas the content of lipids depended on the separation protocol and the resulting product. Still, they did not represent a major group and were thus classified as a potential valuable side-product. Lyophilized algal fractions obtained from D. grisea were found to be not toxic when EPS were not included. Upon implementation of EPS as a commercial product, further assessment on the environmental toxicity to enchytraeids and other soil organisms is required. Our results provide a possible direction for developing a process to gain an environmentally friendly bio-additive for application in the tribological industry based on a biorefinery approach.