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Flame-retardant insulating powder coating is a solid powder coating that uses epoxy resin and other materials as its primary film-forming substances and combines two functions: electrical insulation and flame retardancy. The coating formed after application can prevent electrical breakdown while slowing the spread of flames. It is commonly used in applications with special safety protection requirements, such as electrical components and new energy battery parts.

This article systematically introduces the concept, characteristics, functions, applications, selection considerations, and solutions to common problems associated with flame-retardant insulating powder coatings. It focuses on the functions of flame-retardant insulating powder coatings to help readers better understand what they are, as well as their characteristics and applications.

What Is Flame-Retardant Insulating Powder Coating?

It is a thermosetting powder coating that uses epoxy resin as its primary film-forming material and achieves two functions within the same coating: electrical insulation and self-extinguishing when exposed to fire.

Its insulating properties rely on the epoxy cross-linked network and high-purity fillers, while its flame-retardant properties are provided by either additive flame-retardant systems (such as aluminum hydroxide, magnesium hydroxide, and phosphorus-based systems) or reactive flame-retardant systems. These two properties must be balanced and coordinated within the formulation rather than simply combined.

Characteristics of Flame-Retardant Insulating Powder Coating

Flame-retardant insulating powder coatings have the following characteristics:

1. Electrical Insulation: High volume resistivity and high dielectric strength enable the coating to effectively prevent electrical breakdown. Uniform coverage at edges and corners helps avoid breakdown at locally weak points.
2. Flame Retardancy: UL 94 V-0 is the core acceptance rating. The coating is self-extinguishing when exposed to fire. Additive or reactive flame-retardant systems provide flame-retardant properties, while high-end products also require non-combustibility and low smoke generation.
3. Synergy Between Insulation and Flame Retardancy: Both functions must be balanced within the same coating. Adding large amounts of flame-retardant fillers must not compromise the insulating or mechanical properties.
4. Mechanical Flexibility and Adhesion: The coating must have sufficient flexibility and adhesion to withstand substrate bending and assembly stresses, reducing the risk of cracking.
5. Edge and Corner Coverage: The coating must remain uniform and continuous along substrate edges and complex geometries. This is both a requirement for reliable insulation and an indication of process adaptability.
6. Environmental Resistance: Resistance to electrolytes, salt spray, and aging is required. For new energy applications, additional requirements such as thermal runaway protection must also be met.

Functions of Flame-Retardant Insulating Powder Coating

The functions of flame-retardant insulating powder coatings are reflected in the following aspects:

1. Electrical Insulation Protection

As an electrical isolation layer, it prevents high-voltage components from experiencing electrical breakdown, ensuring the normal operation of equipment and personnel safety. Its insulating properties are achieved through the epoxy resin cross-linked network and high-purity fillers, with volume resistivity reaching above \(10^{15}\ \Omega\cdot\text{cm}\). In new energy applications, it is used on components such as power battery housings, PACK enclosures, connectors, and liquid cooling plates to withstand voltage stresses during operation and charging and discharging processes.

2. Flame Retardancy and Flame Spread Suppression

When exposed to a fire source, the coating can self-extinguish, meet UL 94 flame-retardant rating requirements, and slow the spread of flames and heat. Products designed for thermal runaway protection in power batteries also emphasize resistance to ignition, preventing the coating system from being ignited during thermal runaway propagation. This function provides additional time for personnel evacuation and firefighting and rescue operations, making it a key part of new energy battery safety protection.

3. Replacement of Traditional Insulation Processes

It can replace traditional insulating paint and PP wrapping film processes, enabling fully automated, large-scale coating production while providing more uniform and reliable integrated insulation and flame-retardant protection.

4. Additional Protective Functions

Commercial products also offer electrolyte resistance (for battery-related components), temperature and humidity resistance, and good edge and corner coverage. These properties ensure that insulation reliability is not compromised by thin coating areas on complex geometries.

Specific Application Areas of Flame-Retardant Insulating Powder Coating

Flame-retardant insulating powder coatings are specifically used in the following fields:

1. Traditional Electrical Appliances and Electronic Components

These applications have specific requirements for low-temperature curing to avoid damaging heat-sensitive components. Typical applications include encapsulation of resistors and capacitors in color televisions, encapsulation of high-voltage ceramic capacitors, and slot insulation coating for small and medium-sized motors.

For motor core slot insulation, epoxy powder coatings meet Class B thermal resistance requirements through their excellent edge and corner coverage and metal adhesion. In electrical equipment such as busbars and switchgear cabinets, powder coatings are used for high-voltage insulation, withstanding voltages of several thousand volts while meeting the UL 94 V-0 flame-retardant rating.

2. New Energy Vehicle Battery Systems

This is currently the most important area of growing application for flame-retardant insulating powder coatings. High-voltage components inside power battery packs have dual requirements for insulation reliability and thermal runaway protection. Powder coatings are used on several key components:

Battery Housings and PACK Enclosures: Provide insulation and flame-retardant protection for power battery housings and PACK enclosures while offering electrolyte resistance. They can replace traditional insulating paint and PP wrapping film processes, enabling fully automated, large-scale coating production.

Battery Connectors and Busbars: Conductive components such as connectors and busbars require insulating coatings to prevent short circuits. Polyamide powder coatings combine flexibility and flame retardancy in these applications, and coatings applied to busbars can achieve the UL 94 V-0 rating.

Liquid Cooling Plates and Cooling Systems: Components such as liquid cooling plates in energy storage cabinets and battery cooling plates require thin insulating coatings. Polyamide powder coatings can provide electrical insulation at a thickness of approximately 100 μm while maintaining heat dissipation efficiency.

Thermal Runaway Protection Coatings: For battery pack top covers or module partition plates, specialized powder coatings can resist ignition, expansion, and smoke generation under direct flame exposure, helping delay flame spread during thermal runaway.

3. Energy Storage Systems and Other Applications

Components such as liquid cooling plates and battery racks in energy storage cabinets are also suitable for the above-mentioned insulating and flame-retardant powder coatings. In addition, some products are used in electric vehicles, power facilities, and building infrastructure, providing durable protection in high-temperature, highly corrosive, or coastal environments with high salt and humidity levels.

How to Choose Flame-Retardant Insulating Powder Coating

When selecting flame-retardant insulating powder coatings, we may face difficulties in determining which products to choose. Based on our industry experience, we recommend focusing on the following aspects when selecting flame-retardant insulating powder coatings.

1. Traditional Electrical Appliances and Electronic Components: Curing Temperature Is the Primary Requirement

For heat-sensitive components such as capacitors, resistors, and motor cores, first confirm whether the powder coating’s curing conditions are compatible with the temperature resistance of the components. Some products can be cured at 100°C × 120 min or 120°C × 60 min while achieving the UL 94 V-0 rating.

Epoxy resin is the primary resin used, ensuring insulation performance and adhesion. Regarding flame-retardant fillers, magnesium hydroxide generally provides better flame-retardant performance than aluminum hydroxide because it can promote carbonization on the coated surface, forming a barrier layer.

2. New Energy Vehicle Batteries and Energy Storage: Select According to Two Component Functions

Insulation Protection Components (Battery Pack Housings, Busbars, Connectors, and Liquid Cooling Plates): Choose epoxy-based powder coatings, focusing on edge and corner coverage and electrolyte resistance. Commercial products emphasize uniform edge and corner coverage to ensure a high pass rate in dielectric withstand tests. Typical curing conditions are 180°C/15 min or 200°C/10 min, meeting UL 94 flame-retardant rating requirements. When selecting products, require suppliers to provide adhesion data for the specific substrate and electrolyte resistance test reports.

Thermal Runaway Protection Components (Battery Pack Top Covers and Module Partition Plates): The core requirement is not conventional insulation but resistance to ignition under direct flame exposure. Specialized products must remain non-combustible, non-expanding, and smoke-free under direct flame exposure at 600–1200°C to delay flame spread. During product selection, confirm whether the products have passed relevant tests, such as single-cell thermal runaway tests or UL 2596 TaG, rather than relying solely on a UL 94 V-0 certificate.

Common Problems and Solutions for Flame-Retardant Insulating Powder Coating

The most common problems encountered when using flame-retardant insulating powder coatings are mainly reflected in the following aspects. Based on our industry experience, we have proposed corresponding solutions to help effectively address the powder coating problems you may encounter.

1. Imbalance Between Flame Retardancy and Insulation Performance

Problem Description: After increasing the amount of flame-retardant fillers to achieve the UL 94 V-0 flame-retardant rating, the coating’s volume resistivity, dielectric strength, or flexibility decreases, making it difficult to meet both core performance requirements simultaneously.

Possible Causes: Adding large amounts of additive flame-retardant fillers, such as aluminum hydroxide and magnesium hydroxide, dilutes the continuity of the epoxy resin cross-linked network and introduces more interfacial defects into the coating, creating pathways for electrical breakdown. When aluminum hydroxide is used alone, a very high loading is required to achieve flame retardancy. However, excessive filling can impair mechanical and electrical properties.

Solutions: Adopt a synergistic flame-retardant system instead of relying on a single filler. A bromine-antimony-aluminum hydroxide ternary system can achieve an oxygen index of 37 and the FV-0 vertical burning rating with only 10% aluminum hydroxide, significantly outperforming the use of 50% aluminum hydroxide alone. The use of nanoscale flame-retardant fillers can also improve flame-retardant efficiency at lower loading levels while reducing negative effects on insulation and mechanical properties. Where conditions permit, reactive flame retardants can incorporate flame-retardant groups into the resin backbone, avoiding the side effects associated with excessive filler loading.

2. Pinholes

Problem Description: Dense, tiny holes appear on the coating surface. In insulation applications, these may become starting points for partial discharge or electrical breakdown, potentially causing dielectric withstand tests to fail in severe cases.

Possible Causes: During powder coating film formation, air trapped between loosely deposited powder layers, volatile substances adsorbed on the substrate surface, or gases generated during curing may fail to escape in time when the coating is nearly closed, breaking through the surface and forming pinholes. Insulating powder coatings are commonly used on electrical components and battery parts, where micropores and residual contaminants on the substrate surface are important sources of gas. Excessive film thickness makes gas escape more difficult.

Solutions: Add benzoin (2-hydroxy-1.2-diphenylethanone) as a degassing agent to the formulation. It is an essential measure for eliminating inherent pinholes in high-gloss powder coatings. Strictly control the quality of pretreatment to ensure that the substrate surface is free of oil and residual liquids. Control the film thickness within a reasonable range. For excessively thick coatings, other defoaming agents should be used together with benzoin to address pinholes in thick films. For porous castings or battery housings, consider preheating the substrate to remove adsorbed gases before spraying.

3. Craters

Problem Description: Sunken, circular, crater-like depressions appear on the coating surface, sometimes with a small raised point in the center. These defects damage the continuity and density of the coating and also create weak points in insulation applications.

Possible Causes: Low-surface-tension contaminants, such as dust and oil droplets, may adhere to the substrate or become mixed into the powder. The molten coating flows from areas with low surface tension toward areas with high surface tension, forming craters. Moisture and oil in compressed air are common sources of contamination.

Solutions: Keep the spraying environment and compressed air clean. The air compressor must be equipped with effective oil and water removal devices. Suitable wetting agents can be selected for the powder formulation to disperse contaminant particles that may cause cratering. The workpiece surface must be thoroughly degreased before spraying.

4. Insufficient Edge and Corner Coverage

Problem Description: At substrate edges, corners, or complex geometries, the coating becomes noticeably thinner or even exposes the substrate, creating preferred failure locations for electrical breakdown.

Possible Causes: During electrostatic spraying, the edge effect makes it difficult for powder to be uniformly deposited on sharp edges. During melt flow and leveling, the coating may retract from the edges. Insulating powders with excessively strong leveling properties or excessively low melt viscosity have a higher risk of poor edge and corner coverage.

Solutions: Select insulating powder coating products specifically designed to provide good edge and corner coverage. Commercial epoxy flame-retardant insulating powder coatings already treat uniform edge and corner coverage as a key indicator for ensuring a high pass rate in dielectric withstand tests. Adjust spraying parameters to prevent excessively high voltage from causing powder repulsion or uneven accumulation at the edges. For components with complex structures, the minimum film thickness can be appropriately increased to compensate for edge thinning.

 

Choose High-Performance Flame-Retardant Insulating Powder Coating to Improve the Safety Protection Level of Electrical Equipment

We specialize in the research, development, and production of flame-retardant insulating powder coatings, providing professional product solutions that combine excellent dielectric properties, insulation strength, flame retardancy, heat resistance, and coating adhesion. Formulations can be customized according to different substrate characteristics, application environments, and electrical performance requirements to meet the insulation protection needs of various electrical equipment and metal components.

Contact us for professional product selection advice, technical support, and customized powder coating solutions.