The shift toward renewable energy places new demands on the sustainability of high voltage (HV) electrical infrastructure. HV insulation components must perform reliably for decades under electrical, thermal, mechanical, and chemical stresses. For more than 50 years, epoxy resins have dominated these applications thanks to their strong dielectric and mechanical properties, but they are increasingly challenged due to energy intensive production, difficult recyclability, the presence of bisphenol A (BPA), and misalignment with circular economy expectations [1]–[3], [12]. To address these challenges, this work examines two complementary strategies [4]. First, we review advanced recycling methods for epoxy-based insulation. Mechanical and chemical approaches enable separation and reuse of valuable materials, reducing landfill waste and supporting more circular material flows [2]. Recent innovations have highlighted their potential to improve recyclability [8]–[11]. Second, we discuss the development of next generation thermoplastic insulation systems. Unlike thermosets, thermoplastics are inherently recyclable, lower in environmental impact, and compatible with high-volume manufacturing. Experimental data on dielectric performance, mechanical behavior, thermomechanical stability, chemical compatibility, adhesion, manufacturability, and electrothermal lifetime demonstrate their suitability for future HV applications. By combining improved recycling pathways for existing epoxy-based components with the adoption of sustainable thermoplastic materials in new designs, this approach enhances resource efficiency and supports the power sector's transition toward a more circular and environmentally responsible future.

The energy industry demands high electrical and thermal conductive materials with good manufacturability, highlighting the importance of copper alloys. A significant share of material in each power transformer is copper alloys, from windings and cables to copper contacts and conductors. Current manufacturing methods including hot forging, casting, and machining limit the engineers to design the optimized geometries. Additive manufacturing (AM) is a highly desired layer-by-layer fabrication process from a 3D digital model. Being additive-based, these processes benefit from minimal material waste, freedom of design, reduced time to market, and eliminating the cost of special tooling. In this paper, design for additive manufacturing (DfAM) is employed to optimize the design of candidate copper contacts with the goal of mass reduction and keeping the thermo-electrical requirements standards in transformers. Re-designed copper contacts with 25–53

In the power industry, various electrically insulating materials are used to ensure proper mechanical, thermal, and dielectric performance over decades of equipment operation. In power transformers, cellulose is the predominant material in manufacturing various insulation components. Most of these products are manufactured by wet-molding technology. However, this process is long, labor-intensive, and highly energy-demanding. Under the frame of an EU-funded grant, a new kind of insulation material and manufacturing process were developed. Fully bio-based material (produced in the form of pellets) can be processed using additive manufacturing, allowing for much shorter manufacturing times for insulation products, with considerably less scrap and energy consumption (due to the elimination of the drying stage). The focus of the project was extrusion additive manufacturing technology, but at a later stage, a biomaterial powder was developed, making it possible to print with other technologies. In the paper, comparative studies on various additive manufacturing techniques of newly developed biopolymers have been presented, including extrusion, High Speed Sintering (HSS), and Selective Laser Sintering (SLS). The applicability of such material in power transformers required extensive testing of various properties. These results are discussed in the paper and include: oil compatibility, volume resistivity measurements, permittivity and dissipation factor measurements, determination of partial discharge inception voltage, partial discharges measurement, and breakdown voltage measurements. Although mechanical properties remain below industrial targets, the pioneering results provide a promising route for unique directions toward more sustainable manufacturing of high-voltage cellulose insulation and ideas for improving the material properties during the printing process.

Additive manufacturing (AM) is treated as a significant contributor to sustainability due to lower energy consumption, less material usage and reduced number of wastes generated when comparing with traditional manufacturing technologies. Currently there is a lot of commercial applications of such new technology in number of industry segments. However, such sector as high voltage engineering still struggles with number of challenges when considering additive manufacturing. In products working in high voltage environment, very often, in addition to mechanical loads there are demanding conditions, as elevated temperature and presence of insulation oil or gas. This requires a special approach to printing quality of the printed structures without internal voids and in case of metals, with improved electrical conductivity. In the paper, few examples of additive manufacturing applications in area of power products have been presented, including printed transformer insulation, printed copper, and application of AM for spare parts. For each case, the main challenges have been discussed.

Additive manufacturing offers great potential for various industrial solutions; in particular, the binder jetting method enables the production of components from various materials, including sand molds for casting. This work presents the results of an extensive set of experiments aimed at enhancing the structural strengthening of 3D-printed sand molds. Structural strengthening was achieved by impregnating the sand-printed structures with two polymer materials: epoxy resin and silicone varnish. Impregnation was performed with variable parameters, such as temperature, pressure, and time. Structural strengthening using polymers was investigated by analyzing the flexural strength and impact resistance of the impregnated products and comparing these obtained values with the reference material in terms of impregnation parameters and the polymer used. Microstructural observations and an analysis of the pore filling were also performed. This approach allowed for a full assessment of the influence of processing parameters and the type of polymer used for impregnation on the properties of sand-printed structures, which allowed for identifying the most optimal method to be used to strengthen the sand molds for casting the components for electrical devices. As a direct proof of concept, it was shown that impregnation with polymeric materials could effectively strengthen the sand mold, increasing its flexural strength and impact resistance by over 20 times and 5 times, respectively. A full-scale mold was printed using binder jetting, impregnated with epoxy resin at 65 °C, and used to successfully fabricate a fully functional electrification device.

In recent years, additive manufacturing (AM) has made considerable progress and has spread in many industries. Despite the advantages of this technology including freedom of design, lead time reduction, material waste reduction, special tools manufacturing elimination, and sustainability, there are still a lot of challenges regarding finding the beneficial application. In this study, the feasibility of replacing traditional manufacturing methods with additive manufacturing in the energy sector is investigated, with a specific focus on gas-insulated high-voltage switchgear (GIS). All aluminum parts in one specific GIS product are analyzed and a decision flowchart is proposed. Using this flowchart, printability and the best AM technique are suggested with respect to part size, required surface roughness, requirements of electrical and mechanical properties, and additional post processes. Simple to medium complexity level of geometry, large size, high requirements for electrical and mechanical properties, threading and sealing, and lack of a standard for printed parts in the high voltage industry make AM a challenging manufacturing technology for this specific product. In total, implementing AM as a short series production method for GIS aluminum parts may not be sufficient because of the higher cost and more complex supply chain management, but it can be beneficial in R&D cases or prototyping scenarios where a limited number of parts are needed in a brief time limit.

This article presents a comparative analysis of the crucial physical properties of electrically conductive components made of pure copper, produced by various additive manufacturing technologies such as binder jetting (BJ) and direct metal laser sintering (DMLS). The comparison concerned the assessment of critical parameters important from the application point of view, such as: electrical conductivity, hardness, yield point, microstructure and the occurrence of internal material defects. Same-sized components made in a conventional casting and subtractive method (machining) were used as a reference material. Comprehensive tests and the comparison of a wide range of parameters allowed us to determine that among the selected methods, printing using the DMLS technique allowed for obtaining arcing contact with mechanical and electrical parameters very similar to the reference element. Therefore, the obtained results showed the possibility of using the copper elements made by additive manufacturing for the switching and protection devices used in electrification and energy distribution industrial sectors.

Three-dimensional printing technology is constantly developing and has a wide range of applications; one application is electrical insulation, where the standard technology uses polymer-based filaments. Thermosetting materials (epoxy resins, liquid silicone rubbers) are broadly used as electrical insulation in high-voltage products. In power transformers, however, the main solid insulation is based on cellulosic materials (pressboard, crepe paper, wood laminates). There are a vast variety of transformer insulation components that are produced using the wet pulp molding process. This is a labor-intensive, multi-stage process that requires long drying times. In this paper, a new material, microcellulose-doped polymer, and manufacturing concept for transformer insulation components are described. Our research focuses on bio-based polymeric materials with 3D printability functionalities. A number of material formulations were tested and benchmark products were printed. Extensive electrical measurements were performed to compare transformer components manufactured using the traditional process and 3D printed samples. The results are promising but indicate that further research is still required to improve printing quality.

HV insulation components work in a very harsh environment. These elements, depending on their application, are exposed to high voltage and high temperature (>100C), outdoor work, dielectric gases, and many other conditions. For many years such elements have been produced mainly from thermoset materials with filler, in particular epoxy resin. In general, the current material and its processing lead to a labor-intensive and complex manufacturing process. Additionally, epoxy material is very problematic to recycle thus, it would be desirable to find a material which is easier to process and more ecofriendly. Nowadays, we see more and better polymers like thermoplastics that seem to be good alternative. But their implementation is not an easy task and requires performing a lot of tests which are very challenging. The paper consists of selected HV insulation requirements and examples of tests that must be performed to find the best material candidates. Performed analyses and tests for different thermoplastic materials show its potential for implementation as alternative to epoxy resin. This way seems to be the right one as thermoplastic material offer a lot of benefits especially in terms of sustainability and circular economy.

An effective model to calculate thermal conductivity of polymer composites using core-shell fillers is presented, wherein a core material of filler grains is covered by a layer of a high-thermal-conductivity (HTC) material. Such fillers can provide a significant increase of the composite thermal conductivity by an addition of a small amount of the HTC material. The model employs the Lewis-Nielsen formula describing filled systems. The effective thermal conductivity of the core-shell filler grains is calculated using the Russel model for porous materials. Modelling results are compared with recent measurements made on composites filled with cellulose microbeads coated with hexagonal boron nitride (h-BN) platelets and good agreement is demonstrated. Comparison with measurements made on epoxy composites, using silver-coated glass spheres as a filler, is also provided. It is demonstrated how the modelling procedure can improve understanding of properties of materials and structures used and mechanisms of thermal conduction within the composite.

Materials used for high-voltage electrical insulation must fulfill particular mechanical, thermal, and dielectric requirements, therefore epoxy based composites seem to be perfect ones and are broadly used for that purpose. What is very important, the properties of the final product are strongly dependent on appropriate manufacturing process with lack of material failures, as too large shrinkage, voids and cracks. Combination of proper materials (epoxy, hardener, and filler) and process parameters (mould temperature, filling time, filling velocity, initial temperature of internal parts, gelation time), as well as design and geometric parameters are essential to assure high quality of the produced components. Here, an application of advanced numerical simulations plays a very important role in identification of potential problems already during design of new products (and before a mould order) and by application of such “virtual” prototyping the best process parameters can be defined minimizing a probability of quality issues. These aspects have been covered in first part of that article.

The epoxy resin-based systems with silica filler are widely used in many products like medium and high voltage electrical components due to its very good dielectric and mechanical properties. Such products require to operate in harsh environments which may activate the process of formation and propagation of the cracks within the resin material. The cracking phenomenon contributes also to manufacturing problems. The epoxy based parts are very often produced by casting during which (post) curing cracking may appear.In order to better understand the cracking phenomena of epoxy resin there is a need to investigate microstructural damage. The work presented in this paper includes both experimental and numerical analysis of microstructure crack initiation and propagation in silica filled epoxy. Basic information about epoxy resin-based systems and its applications are presented. Next, basics of the fracture mechanics with description of available numerical approaches are described. The numerical simulations were prepared for Representative Volume Element (RVE) which was obtained using home-made tool for image digitalization. Experimental analysis consist of in-situ tensile tests and microstructural observations with Scanning Electron Microscope (SEM). At the end a summary with conclusions related with prepared numerical analysis and experiments is included. The presented research of the damage of silica/epoxy composite confirms that analysis of the epoxy resin microstructural damage is not trivial and further study is required for its better understanding. Copyright (C) 2016 The Authors. Published by Elsevier B.V.

An appropriate filler is a key component required to achieve an useful composite with expected properties. Not only sophisticated types of filler, like graphene are popular, but also more common ones, like silica flour or fly ash because of their low costs. Besides production costs, adequate size and possibility of functionalization of particles surface to create stable bonds with a matrix are essential in filler selection. To create an useful filler for epoxy resin based composites with use of a waste material, namely fly ash, two-step procedure was proposed. In the first part, raw material was sieved and five different ranges of the filler size were obtained. After mechanical tests with fracture toughness, tensile strength and Young Modulus, as well thermal conductivity, the best size of the fly ash was chosen for further modification. During the second step, filler was modified with coupling agent [3-(2-aminoethylamino)propyl]trimethoxysilane in order to enhance the coupling between particular components of composite. Presence of the silane layer was confirmed with infrared spectroscopy and scanning electron microscopy measurements, whilst prepared epoxy composite filled with silanized fly ash was examined similarly as previous composites. Obtained results have proved the significant influence of size of a filler and bonding to the matrix on mechanical and thermal properties of fly ash-epoxy resin composite. Proposed simple method of fly ash modification is an environmentally friendly way for utilization of the fly ash. Moreover, it creates an alternative material applicable in electrical devices as functional composite.

The insulation material of electronic devices should offers high thermal conductivity whilst retaining suitable mechanical properties. Epoxy resin is an example of a material that is commonly used by industry for electronic insulation, despite the fact that neither the thermal conductivity nor the mechanical properties are particularly satisfying. These properties can be enhanced by incorporating filler, with silica flour representing the most popular filler. An economically appealing solution is to replace silica flour with fly ash as filler material, however it must be remembered that compatibility of fly ash and epoxy resin is not ideal. In order to improve the coupling between these two materials, fly ash particles covered with [3-(2-Aminoethylamino)propyl]trimethoxysilane were obtained with six different conditions of the silanization process, where the amount of silane, the temperature and the time of the reaction were changed. The presence of the silane layer was confirmed via Fourier Transform Infrared Spectroscopy, Thermogravimetric Analysis and Scanning Electron Microscopy. The mechanical properties, including tensile strength, Young Modulus and fracture toughness, as well as the thermal conductivity of the final samples were investigated. In the case of composites with silanized fillers, all of the mechanical properties were improved, and an enhancement of thermal conductivity was observed for several composites. Moreover, the differences in coupling between the silanized fly ash and the untreated fly ash, and the epoxy matrix were precisely recorded by means of SEM. The presented studies confirm that an effective silanization process can significantly improve the properties of composites, while also verifying the usefulness of waste material. The results highlight that fly ash may be utilized to create a more economically affordable insulation material.

The aim of the presented work is to show the influence of the various polymer matrices and the different amounts of the cellulose filler on the composites properties. Samples based on polypropylene, polystyrene, polyoxymethylene, acrylonitrile butadiene styrene, polyester resin, and polylactic acid with different contents of cellulose fibers were prepared by injection molding process. The mechanical and dielectric properties of these composites were studied in order to check whether investigated wood polymer composites fulfill requirements for their application in electrical devices. For all tested composites, a linear increase of modulus with cellulose content was observed. Addition of cellulose to the tested polymers significantly reduces strain at break. In the case of polypropylene and polyoxymethylene composites, the tensile strength increases with the content of the filler. For other materials, there is an inverse relationship, namely the addition of cellulose decreases the tensile strength. The electrical strength decrease was observed with increased cellulose content for the majority of the investigated composites. Polar groups incorporated by cellulose fibers have led to dielectric constant increase. Furthermore, aging of composites in mineral oil and evaluation of water uptake for wood–plastic samples were performed. Wood polymer composites have changed significantly after aging. The water diffusion coefficients were determined, and the significant influence of the amount of cellulose on the water absorption was shown. Copyright © 2015 John Wiley & Sons, Ltd.

This paper investigates the influence of magnetic field-assisted filler alignment technology on the morphology and the thermal conductivity of magnetite-filled epoxy composites. A magnetic field was applied during the solidification of the composite in order to change the position of the filler and its distribution in the polymer matrix. It is shown that the applied procedure leads to the filler being oriented along the direction of the magnetic field, and as a result, the thermal conductivity is improved by up to 120 % compared to a composite with randomly oriented filler obtained without the assistance of a magnetic field. This positive effect is caused by the appearance of conductive paths at a much lower content of the filler when the composite solidification is assisted by a magnetic field, relative to an equivalent isotropic sample. These morphological changes were confirmed by microscopic and X-ray microtomography imaging. The temperature dependences of thermal conductivity were also investigated over a broad temperature range for a magnetite-filled epoxy composite sample and compared to the bulk magnetite reference, showing that thermal behaviour of the magnetite-filled composite is stable, which is a promising result when considering the future application of the technology.

The results of thermal conductivity study of epoxy–matrix composites filled with different type of powders are reported. Boron nitride and aluminum nitride micro‐powders with different size distribution and surface modification were used. A representative set of samples has been prepared with different contents of the fillers. The microstructure was investigated by SEM observations. Thermal conductivity measurements have been performed at room temperature and for selected samples it was also measured as a function of temperature from 300 K down to liquid helium temperatures. The most spectacular enhancement of the thermal conductivity was obtained for composites filled with hybrid fillers of boron nitride–silica and aluminum nitride–silica. In the case of sample with 31 vol.% of boron nitride–silica hybrid filler it amounts to 114% and for the sample with 45 vol.% of hybrid filler by 65% as compared with the reference composite with silica filler. However, in the case of small aluminum nitride grains application, large interfacial areas were introduced, promoting creation of thermal resistance barriers and causing phonon scattering more effective. As a result, no thermal conductivity improvement was obtained. Different characters of temperature dependencies are observed for hybrid filler composites which allowed identifying the component filler of the dominant contribution to the thermal conductivity in each case. The data show a good agreement with predictions of Agari‐Uno model, indicating the importance of conductive paths forming effect already at low filler contents. Copyright © 2014 John Wiley & Sons, Ltd.