On March 18, the Sub-Motor Division of the China Electricity Council hosted 2021 China Electric Motor Industry and High-Efficiency Energy-Saving Technology Development Forum Held in Guangzhou.

On the forum, Zhang Haiwen, Sales Director, DADIYUAN New Materials Co., Ltd., Shunde, Guangdong , introducing the differences between water-emulsion epoxy insulation coatings and water-based insulation coatings, with a focus on highlighting the core advantages of water-emulsion epoxy insulation coatings and their excellent cost-effectiveness. Additionally, based on the application process of water-emulsion epoxy insulation coatings, we provide five key points to consider when using this product.

Looking back briefly at the development of China's insulation coating industry over the past five decades, we’ve seen a gradual shift—from the initial solvent-based systems—commonly known as oil-based coatings containing high levels of solvents like toluene and xylene—to today’s waterborne alternatives. This evolution clearly demonstrates that China’s insulation industry has been advancing product innovation and embracing environmental sustainability in roughly 10-year cycles.

The differences between water-soluble epoxy and other water-based insulants

From a water-based perspective, there’s water-soluble and water-based—so what exactly is the difference between these two? Can water-based paint really be used on motors? I often hear the claim: "How can water possibly provide insulation?" Personally, I believe that water-based insulating paints—especially water-emulsion epoxy insulating paints—are perfectly suitable for use in small and medium-sized motors, as well as fractional-horsepower motors. What exactly is the difference between water-soluble insulating paint and water-based insulating paint, as just mentioned? Here's a simple comparison.

From a water-based perspective, there’s water-soluble and water-based—so what exactly is the difference between these two? Can water-based paint really be used on motors? I often hear the claim: "How can water possibly provide insulation?" Personally, I believe that water-based insulating paints—especially water-emulsion epoxy insulating paints—are perfectly suitable for use in small and medium-sized motors, as well as fractional-horsepower motors. What exactly is the difference between water-soluble insulating paint and water-based insulating paint, as just mentioned? Here's a simple comparison.

Another notable difference lies in their curing mechanisms: alkyd polyester-based systems typically rely on amino-based curing, which releases gases when heated—gases that can cause discomfort among on-site workers, such as tearing eyes, throat irritation, and nasal discomfort. In contrast, waterborne epoxy emulsions use an epoxy curing agent, eliminating these irritating and uncomfortable effects altogether. Moreover, due to the inherent differences in resin composition and curing systems, these water-based insulating varnishes exhibit significantly varying performance characteristics—particularly in terms of electrical, mechanical, and physical properties—making them suitable for distinct applications.

The advantages of water-soluble epoxy insulating paint

Compared to The ones introduced above Several in terms of , water-based epoxy insulation coatings have a key advantage: excellent penetration and filling performance, especially when it comes to the secondary insulation and reinforcement of electromagnetic wires. Additionally, these coatings ensure even application—both top and bottom—with superior moisture resistance. Here, "moisture resistance" refers to the fact that, unlike some other water-borne insulating paints (such as alkyd, acrylic, or polyester-based ones), which may reabsorb moisture or even deliquesce after curing due to water acting as a carrier, water-emulsion epoxies stand out for their inherent ability to maintain dryness and stability over time. Finally, these coatings boast exceptional adhesion and bonding strength—undoubtedly, among commonly used insulation paints, epoxy coatings offer the strongest adhesive properties and the best overall bond integrity.

In addition to its core advantages, water-emulsion epoxy insulation paint stands out due to its extremely low solvent content, making it non-flammable and highly safe. It’s also environmentally friendly, with minimal odor, while delivering exceptional performance—such as preventing wire strands from scattering after application—and offering superior bonding strength. Moreover, its cost-effectiveness makes it an outstanding choice for practical use.

Economic Calculation for Water-Based Epoxy Insulating Coating

How does cost-effectiveness manifest itself? Let’s compare water-based paint with traditional oil-based paint using a customer case study. Water-based paint has a wet film thickness of 12.5 grams per coat, whereas oil-based paint requires 14.75 grams per coat. As a result, water-based insulating paint uses slightly less material compared to its conventional oil-based counterpart. Additionally, there’s a significant difference in evaporation rates: water-based paint evaporates at 78 grams, while oil-based paint evaporates at an astonishing 2,453 grams. This stark contrast in evaporation rates directly influences the overall cost of application. When calculating costs based on coating weight alone, the difference between the two paints isn’t substantial. However, the issue of volatility plays a crucial role. Oil-based paint evaporates extremely quickly—something anyone who’s used it can easily confirm, especially in open-type paint trays. Over the course of just one day, the amount lost to evaporation and waste is truly staggering. In contrast, water-based paint evaporates far more slowly. When you factor in all these considerations—material usage, evaporation rates, and overall efficiency—the total cost of using water-based paint turns out to be significantly lower than that of oil-based paint. The chart below presents the actual measured data.

Typical Application Process for Water-Based Epoxy Insulating Coating

To Water-emulsifiable epoxy insulating paint typically follows a fairly standard application process, with the most common method being dip coating. After the dipping process, it is baked in an oven. The second one is continuous. Regarding immersion coating machines, I personally believe that a continuous immersion system is the most ideal choice for water-based paints. Of course, its production efficiency does come with certain limitations. For instance, if a particular customer requires a significantly high daily output, a continuous immersion machine might not be able to fully meet their production needs. The third type is Continuous dip coating is a truly excellent process, as it can easily meet production volumes of tens of thousands of units per day—just like some of our customers who already produce several tens of thousands of units daily using this method. One of the biggest advantages of continuous dip coating is that it helps preserve the paint as much as possible. The final method is VPI Immersion under vacuum delivers better vacuum penetration performance.

When using water-based epoxy insulation coatings—regardless of the application method, whether it’s dip coating or continuous immersion—the three key factors are time, temperature, and ventilation. If even one of these critical elements is not properly met, the water-based epoxy insulation coating may suffer from inherent shortcomings during use. Therefore, it’s important to pay attention to the following points in practical applications:

1. The curing and film-forming mechanism of waterborne epoxy emulsions differs from that of other water-based paints and solvent-based epoxy coatings. In this process, crosslinking occurs as water evaporates, enabling inter-particle penetration, internal diffusion, and ultimately leading to a crosslinked reaction. Therefore, controlling the curing temperature, ensuring adequate baking time, and managing moisture vapor release are particularly critical.

2. Curing temperature ≥120°C, baking time ≥90 minutes,

3. Continuous immersion equipment and suspended dip-coating systems feature excellent ventilation and exhaust capabilities, ensuring they meet vapor emission requirements.

4. The exhaust valve and blower of the vacuum impregnation equipment must remain open. If the connecting pipe is designed for high-altitude emission, a centrifugal separator should also be installed for added protection, while ensuring that condensate backflow is carefully avoided.

5. For the bread oven, an external centrifugal fan must be installed to enhance ventilation. Inside the oven, a blower should be fitted to ensure circulating hot air. Additionally, make sure there’s adequate space between the upper and lower tool racks to prevent overcrowding. If the oven is connected to exhaust ducting, avoid excessively long pipes or numerous bends—otherwise, another centrifugal fan will need to be added.