Alkyd resins (ARs) represent a significant development in synthetic polymers, being among the oldest ones and playing a crucial role in numerous applications, especially within the coating sector. The trend is moving towards replacing non-renewable resources in the production of ARs with bio-based alternatives, with the goal of creating more sustainable binder materials as part of the transition to a bioeconomy. 2,5-Furandicarboxylic acid (FDCA) serves as a promising biomass-derived “building block” to replace non-renewable petroleum-derived aromatic diacids and anhydrides in AR synthesis. Various vegetable oils, including sunflower seed (SFO) and linseed oils (LSO), were utilized along with pentaerythritol (P) and glycerol (G) as polyols. FTIR and ¹H NMR spectroscopies were conducted for the verification of alkyd structures. The synthesized ARs were assessed for their physico-chemical properties, including acid value, hydroxyl value, color, density, and viscosity. The performance of the resulting alkyd coatings, which are crucial for their commercial applications, was examined. Key factors such as drying time, hardness, adhesion, wettability, chemical and corrosion resistance, and UV stability were analyzed. All synthesized FDCA-based alkyd coatings demonstrate outstanding adhesion, good thermal stability up to 220 °C, and barrier properties for steel with |Z|_0.02Hz ~10⁶–10⁷ Ohm cm⁻², which render them suitable for the processing requirements of indoor coating applications. The higher temperature at 50% mass loss (T₅₀) for SFO-P (397 °C) and LSO-P (413 °C) as compared to SFO-G (380 °C) and LSO-G (394 °C) indicated greater resistance to thermal breakdown when pentaerythritol was used as a polyol. Replacing glycerol with pentaerythritol in FDCA-based ARs resulted in a viscosity increase of 1.2–2.4 times and an enhancement in hardness from 2H to 3H. FDCA-based ARs exhibited decreased tack-free time, enhanced thermomechanical properties, and similar hardness as compared to phthalic anhydride-based ARs, underscoring the potential of FDCA as a sustainable alternative to phthalic anhydride in the formulation of ARs, integrating a greater proportion of renewable components for wood coating applications.

Managing polymer waste, primarily polyolefins—low- and high-density polyethylene and polypropylene—is a critical challenge in the transition to a low-carbon, circular economy. Traditional approaches (landfilling and incineration) are inconsistent with sustainable development principles and increasingly stringent extended producer responsibility regulations, while chemical recycling, particularly catalytic pyrolysis, is considered a key technology for returning hydrocarbon feedstocks to the production cycle. This mini-review systematizes and analyzes current advances in the catalytic pyrolysis of polyethylene and polypropylene. An algorithm for selecting a recycling route for polyolefin-containing waste based on its composition, degree of degradation, and the presence of hazardous additives is proposed. Existing and planned industrial projects in the field of chemical recycling of polyolefins are assessed, and challenges and prospects for technology commercialization are outlined. It is demonstrated that catalytic pyrolysis has the potential to become a key element of a circular economy for plastics, ensuring decarbonization and resource conservation with further optimization of catalysts and process flowsheets.

Metal-coated polymer electrodes fabricated by additive manufacturing are promising tools for electrical discharge machining (EDM) of complex shapes; however, coating non-uniformity and thermomechanical degradation limit their performance. This study presents experimental and theoretical results for a hybrid tool electrode fabricated by stereolithography (SLA), followed by electroless and electrochemical copper plating, and used to machine St3 structural steel. Optical and scanning electron microscopy, energy-dispersive spectroscopy (EDS), atomic force microscopy, X-ray microtomography, Raman spectroscopy, simultaneous thermal analysis and nanoindentation were used to characterize the coating before and after EDM. The electroplated copper layer exhibited pronounced thickness non-uniformity (264–1225 µm), an edge effect and dendritic morphology associated with the primary current distribution and the absence of leveling additives. Surface modification during EDM was accompanied by changes in the elemental composition measured by EDS. After EDM, the Fe and C signals reached 23.32 wt.% and 35.56 wt.%, respectively, under the acquisition and quantification conditions used. These values characterize local surface composition and do not establish bulk incorporation of iron or carbon into the copper layer. No pronounced bulk thermal degradation was detected in the examined photopolymer specimens; exposure of the polymer base nevertheless promotes local damage. A coupled numerical model combines a boundary element calculation of copper deposition, normal coating recession and cavity formation; a single-discharge thermal solver provides diagnostic calculations. The model describes the principal copper-wear and cavity development trends for the investigated electrode, including the end face and chamfer and reproduction of coating and printing defects. Because only one electrode was fabricated, plated and tested, the work is presented as a detailed case study. The observed variability reflects within-specimen measurement scatter and spatial heterogeneity rather than reproducibility between independently manufactured electrodes. The results demonstrate the feasibility of SLA-printed copper-plated electrodes for EDM and identify coating uniformity, adhesion and thermal damage as factors affecting dimensional stability and service life. A solid copper control was not tested under identical conditions, so no direct experimental comparison of machining performance or wear resistance is presented. Seven residual thicknesses determine the deposition parameters, and three working-surface thicknesses determine two effective EDM parameters; all ten locations are calibration data. The mean absolute relative discrepancy is 1.47% for the working locations and 4.42% for all locations. These are fitting metrics. The calculated cavity depth of approximately 8.4 mm and steel removal rate of approximately 35 mm³/min have not been independently measured. Numerical verification and sensitivity analysis are distinguished from independent experimental validation.

Chemical recycling of polyethylene terephthalate (PET) with decomposition into monomers suitable for resynthesizing primary polymer is a critical task for achieving carbon neutrality in the polyester industry. This paper presents a study comparing PET depolymerization solvolysis in tetrahydrofuran medium using a series of metal octoates (Co, Mn, Zn, Ca, Ba, Li, Zr, Cu, Pb). The resulting terephthalic acid (TPA) was characterized using a combination of methods (¹H NMR, thermogravimetric analysis, differential scanning calorimetry, and Raman spectroscopy). In an aprotic tetrahydrofuran (THF) medium, a comparative performance of commercial metal octoates under fixed metal-mass loading was conducted for the first time: the leadership of Co (83.7%) and Pb (78.4%) is explained by the lability of their coordination sphere, while the anomalously low activity of Zr (17.5%) is associated with steric blocking of the metal active center. In the present work, the influence of technological parameters on the depolymerization process using the most active catalyst, cobalt octoate, was studied. It was found that increasing the reaction time from 1 to 6 h leads to an increase in PET conversion from 27% to ~85%, and in TPA yield from 14% to ~84%. A study of the influence of water content in the reaction mixture showed that increasing the water concentration to 20 wt.% intensifies hydrolysis, promoting an increase in the yield of TPA to ~80%; however, a further increase in the water content (up to 30 wt.%) does not lead to a significant change in the yield, which indicates the achievement of conditions providing the highest observed isolated TPA yield within the tested range for the reaction in this system. The obtained results create a scientific basis for the rational design of catalytic systems for the depolymerization of PET, adapted to the different qualities of secondary raw materials and the technological requirements of industrial chemical recycling.

The fabrication of tool electrodes with complex geometries remains a major technological challenge in electrical discharge machining (EDM). This critical review analyzes a hybrid strategy that combines additive manufacturing of a polymer core with subsequent electroless and electrolytic copper deposition to obtain electrically conductive tool electrodes. The principal 3D printing technologies—FDM/FFF, SLA/DLP, SLS, and PolyJet—are compared for polymer core fabrication. By the considered criteria, FDM/FFF and SLA/DLP show the greatest practical potential for polymer cores for subsequent metallization. FDM/FFF offers equipment/material availability and process flexibility; SLA/DLP provides lower surface roughness and higher dimensional accuracy. FDM parameters – layer thickness, nozzle temperature, infill density, and build orientation – are examined for effects on geometric accuracy, surface roughness, and thus metal coating adhesion and uniformity. Primary metallization methods (electroless deposition, physical vapor deposition, conductive pastes) and subsequent copper electroplating are analyzed. A synthesis of experimental data shows that in most studies that included a comparison with a solid copper tool electrode, electrodes with a printed polymer core (mainly ABS) and a copper coating provided comparable material removal rate, wear, and machined surface roughness under finishing and semi-finishing conditions; at the same time, in several studies the hybrid electrodes were inferior to solid copper in material removal rate or wore 1.1–2.8 times faster, and data on the service life of the copper shell are lacking. Optimizing FDM parameters and selecting a metallization method should be treated as interdependent stages of an integrated process chain determining hybrid tool electrode performance.