Introduction to the Advantages of Water-Based Epoxy Insulating Coatings in Fractional-Horsepower Motors

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, starting from the application process of water-emulsion epoxy insulation coatings, we present 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 environmentally friendly waterborne alternatives. This evolution clearly demonstrates that China’s insulation industry has been advancing product innovation and embracing greener practices 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 paint—so what exactly is the difference between the two? And can water-based paints actually be used on electric motors? I often hear the claim that "How can water provide insulation?" Personally, I believe water-based insulating paints—especially water-emulsion epoxy insulants—are perfectly suitable for use in small to medium-sized motors and fractional-horsepower motors. But what exactly sets water-soluble insulating paints apart from water-based ones? Here’s a simple comparison to clarify.

From a water-based perspective, there’s water-soluble and water-based paint—so what exactly is the difference between the two? And can water-based paints actually be used on electric motors? I often hear the claim that "How can water provide insulation?" Personally, I believe water-based insulating paints—especially water-emulsion epoxy insulants—are perfectly suitable for use in small to medium-sized motors and fractional-horsepower motors. But what exactly sets water-soluble insulating paints apart from water-based ones? Here’s a simple comparison to clarify.

Another significant difference lies in their curing methods: alkyd polyesters generally rely on amino-based curing systems, which, when heated, undergo decomposition. This decomposition can cause discomfort among workers on-site—such as tearing eyes, throat irritation, and nasal discomfort. In contrast, waterborne epoxy emulsions use epoxy curing agents, eliminating these irritating and uncomfortable sensations altogether. Moreover, due to the inherent differences in resin composition and the distinct curing mechanisms, the performance of these water-based insulating varnishes—particularly their electrical, mechanical, and physical properties—varies considerably across the different formulations.

The advantages of water-soluble epoxy insulating paint

Compared to the several types introduced earlier, water-based epoxy insulation coatings have a key advantage: excellent penetration and filling capabilities, especially when it comes to providing secondary insulation and reinforcement for electromagnetic wires. Additionally, these coatings ensure even application—both top and bottom—and offer superior moisture resistance. Here, "moisture resistance" refers to the fact that, unlike other water-borne insulating paints (such as alkyd, acrylic, or polyester-based formulations), which may regain moisture or even deliquesce after curing due to water acting as a carrier, water-based epoxy coatings stand out with their inherent ability to maintain dryness over time. Finally, in terms of adhesion and bonding strength, epoxy coatings undeniably boast the highest adhesive and cohesive properties among commonly used insulation paints.

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, emits minimal odor, and delivers exceptional performance—such as preventing wire unraveling after insulation—and boasts superior bonding strength. Moreover, its cost-effectiveness makes it an outstanding choice for practical applications.

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 real-world customer case. When it comes to coating weight, water-based paint uses 12.5 grams per application, whereas oil-based paint requires 14.75 grams—so water-based insulation paint actually uses slightly less material compared to its conventional counterpart. Moreover, 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 final cost of use. At first glance, when calculating costs based on coating quantity alone, the difference between the two isn’t huge. 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-style paint trays. Over the course of just one day, the amount lost to evaporation and waste can be truly alarming. In contrast, water-based paint evaporates far more slowly, minimizing both loss and waste during application. When you factor in these differences, the overall cost of using water-based paint turns out to be significantly lower than that of oil-based paint. The chart below shows the actual measurement data.

Typical Application Process for Water-Based Epoxy Insulating Coating

There are several typical application processes for water- and emulsion-based epoxy insulating coatings. The most common is the dip-and-hold method, where components are immersed and then baked in an oven afterward. Another approach is the continuous immersion machine, which I personally believe is the ideal choice for water-based coatings—though it does come with certain limitations in terms of production efficiency. For instance, if a customer requires very high daily output volumes, the continuous immersion process might not fully meet their manufacturing needs. A third option is continuous hanging-dip, a highly efficient process that can easily handle production volumes of tens of thousands of units per day. In fact, many of our customers already achieve this level of output effortlessly using the continuous hanging-dip method. One of the key advantages of continuous roll-dip is its ability to maximize paint retention during the dipping process. Finally, there’s VPI dip-and-hold, a technique that offers excellent vacuum impregnation 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 during application:

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, as well as 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 vented at an elevated height, a centrifugal separator should also be installed for added protection, while ensuring that condensate does not flow back into the system.

5. For the bread oven, an external centrifugal fan should be installed to enhance ventilation, and a blower must be placed inside the oven to circulate hot air. Additionally, ensure there’s adequate spacing between the upper and lower layers when arranging tools, preventing overcrowding within the oven. If the oven is connected to exhaust ducts for steam removal, these shouldn’t be excessively long or feature too many bends; otherwise, an additional centrifugal fan will be necessary.