5 Critical Mistakes When Working with Insulating Resins in Electrical Engineering and How to Avoid Them
Insulation is the foundation of safety and reliability in electrical engineering. Yet, mistakes are often made when handling insulating resins, which can lead to component failure, reduced lifespan, or safety risks. How can these be prevented?
Photo: Shavr IK / Unsplash
Insulating electrical components with resins is a key process that ensures not only functionality but also the safety of equipment. Whether it involves potting transformers, protecting printed circuit boards, or insulating high-voltage parts, improper handling of insulating resins can have fatal consequences. From insufficient mixing to poor storage conditions and ignoring moisture, these mistakes are often repeated even in established operations. Yet, eliminating them requires only adherence to a few basic rules and technical principles. In this article, we will explore the five most common errors and specific procedures to prevent them.
1. Inadequate surface preparation before application
The first and often underestimated mistake when working with insulating resins in electrical engineering is inadequate surface preparation. Even high-quality resin will fail if the substrate is not properly cleaned and degreased. Residues of oils, dust, or oxides can significantly reduce adhesion, leading to delamination, bubble formation, or even loss of insulating properties. Before application, it is essential to mechanically clean the surface (e.g., by grinding or sandblasting) and then degrease it with a suitable solvent that does not damage the substrate material or the resin itself.
Another critical step is moisture control. A damp surface or high relative humidity (typically above 60%) can cause the formation of microbubbles in the resin, which weaken its insulating properties. It is recommended to work in a climate-controlled environment and dry the surface before application, for example, using a hot-air gun. For sensitive applications, such as high-voltage components, it is advisable to perform an adhesion test on a sample before final application.
2. Incorrect Mixing of Resin Components
Insulating resins are often supplied as two-component systems, where the precise ratio and thorough mixing determine the final mechanical and electrical properties. A common mistake is failing to adhere to the specified weight or volume ratio of the components, which can result in incomplete curing, reduced temperature resistance, or increased brittleness. For example, an excess of hardener can cause excessive shrinkage, while insufficient hardener prolongs curing time and reduces strength.
Another issue is insufficient or uneven mixing, which leaves local areas with unconnected resin. This can lead to the formation of weak spots in the insulating layer, where breakdowns or short circuits occur. To ensure a homogeneous mixture, it is recommended to use a mechanical stirrer with low speed (to minimize air entrainment) and to mix for the time specified by the manufacturer, typically 2–5 minutes. For larger volumes, it is advisable to pour the mixture between containers to ensure even mixing.
Photo: Shavr IK / Unsplash
3. Ignoring temperature conditions during processing
Temperature has a fundamental impact on the viscosity, processing time, and curing of insulating resins. Excessively low temperatures (below 15 °C) increase viscosity, making application difficult and potentially leading to insufficient material saturation or the formation of voids. Conversely, excessively high temperatures (above 30 °C) accelerate curing, shorten processing time, and increase the risk of an exothermic reaction, which can damage surrounding components or cause deformations.
For optimal results, it is essential to adhere to the temperature range recommended by the manufacturer, typically between 20–25 °C. If working in extreme conditions is necessary, temperature-controlled containers or heated applicators can be used, but the processing time must be carefully monitored. For large volumes of resin, it is advisable to divide the application into smaller batches to prevent overheating. It is also important to control storage temperature – resins should be kept in a dry environment at 15–25 °C to avoid degradation or premature curing.
4. Incorrect Storage and Expiration of Resins
Insulating resins have a limited shelf life, which is significantly reduced by improper storage. The most common mistake is exposing resins to moisture, temperature fluctuations, or direct sunlight. Moisture can cause hydrolysis of certain components, leading to reduced mechanical properties and adhesion. Temperature fluctuations can accelerate resin aging or cause component separation, particularly in two-component systems.
For long-term storage, it is crucial to follow the manufacturer's instructions, typically in sealed original packaging, in a cool and dry place. Before use, it is necessary to check the expiration date and the visual condition of the resin – changes in color, cloudiness, or sedimentation are signs of degradation. For two-component systems, it is important to store the components separately and allow them to acclimatize to the working temperature before mixing. If there are any doubts about the quality of the resin, it is advisable to perform a test application and verify its properties using standard testing methods.
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5. Underestimating the impact of moisture on insulation properties
Moisture is one of the most insidious enemies of insulating resins, particularly those based on epoxies or polyurethanes. Even relatively low air humidity (above 50%) can cause water molecules to bind to the reactive groups of the resin, leading to the formation of microbubbles or incomplete curing. The result is reduced dielectric strength, increased permittivity, and in extreme cases, mechanical failure of the insulation. The problem is particularly evident in thin layers or when applied to porous materials such as paper or wood, which easily absorb moisture.
Prevention involves several steps: work in an air-conditioned environment with controlled humidity (ideally below 40%), use air dryers or an inert atmosphere (e.g., nitrogen) for sensitive applications. Always check the substrate moisture before applying the resin – for epoxies, the critical value is usually below 0.5% by weight. Store resins in hermetically sealed containers with desiccants (e.g., silica gel) and allow containers to acclimatize to the working temperature before opening to prevent condensation. When mixing components, use containers and tools dried in an oven or heated to a temperature above the dew point of the surrounding air.
6. Failure to Observe Pot Life and Curing Time
Every insulating resin has a defined pot life, during which it must be applied before it begins to lose its properties. Exceeding this time leads to insufficient flow, poor surface wetting, or even premature curing in the application equipment. Conversely, curing that is too rapid, for example due to high temperature or incorrect catalyst ratio, can cause internal stress, cracks, or insufficient adhesion. These defects often only become apparent after several weeks or months of operation, when repairs are costly or impossible.
Follow the recommended mixing ratios and temperature conditions specified in the technical data sheet precisely. Use timers or automatic dispensers to control the processing time, especially in serial production. To monitor the degree of curing, you can use methods such as DSC (Differential Scanning Calorimetry) or hardness measurements according to standard test methods. For two-component systems, always mix the resin with the catalyst first, and only then add fillers or colorants to avoid local acceleration of the reaction. After application, ensure uniform curing – for example, in an oven with air circulation – and avoid sudden temperature changes that could cause stress in the material.
7. Neglecting Compatibility with Surrounding Materials
Insulating resins often come into contact with various materials – metals, plastics, ceramics, or elastomers. Mismatches in coefficients of thermal expansion, chemical reactivity, or mechanical properties can lead to delamination, corrosion, or degradation of surrounding components. For example, some epoxy resins may react with copper to form salts that impair electrical conductivity or cause cracking in solvent-sensitive thermoplastics. With polyurethane resins, there is a risk of reaction with moisture contained in some plastics, leading to gas formation and bubbles.
Before applying the resin, always verify compatibility with surrounding materials according to technical data sheets or laboratory tests. For critical applications, conduct aging tests under conditions simulating the real operating environment (temperature, humidity, chemicals). If in doubt, use barrier coatings or primers to improve adhesion and protect sensitive materials. Also, ensure that the resin does not contain volatile components that could migrate into surrounding materials and cause their degradation. When selecting a resin, consider not only electrical properties but also the mechanical and chemical requirements of the entire assembly.
Do you need to secure the right raw materials for your production?
Every insulation resin requires specific storage and application conditions. GCG Group provides detailed technical and safety data sheets for each supplied raw material, including handling recommendations. Our experts will be happy to advise you on selecting the appropriate resin type for your specific application and help optimize processes in your production. Contact us – or browse our catalog of over 1,300 products right away.
