HPMC or HEC: Picking the Best Summer-Performing Thickener for ...

When it comes to water-based paint, the choice of thickener can drastically impact the product's performance, especially under summer conditions characterized by high temperatures. Both Hydroxypropyl Methyl Cellulose (HPMC) and Hydroxyethyl Cellulose (HEC) have emerged as popular thickening agents in the paints industry due to their unique properties and varying strengths. These cellulosic additives, supplied by companies like JINJI CHEMICAL, have seen extensive application due to their versatile nature. However, the decision between HPMC and HEC ultimately depends on the specific requirements of the paint formulation and its intended application.

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Understanding HPMC and HEC

HPMC and HEC are both water-soluble polymers derived from cellulose, renowned for their ability to modify viscosity, rheology, and film properties in paints. Despite their common application, they display distinct chemical structures and characteristics that influence their suitability for specific uses.

Hydroxypropyl Methyl Cellulose (HPMC)

HPMC is a cellulose ether with hydroxypropyl and methyl groups, offering excellent water solubility and stability in aqueous systems.

It provides robust thickening and stabilizing effects, making it ideal for formulating paints with smooth, consistent textures. Notably, HPMC exhibits thermogel behavior (reversible gel formation at elevated temperatures, typically 50°C–90°C, higher methoxy content lowers gel temperature), enhancing its suitability for high-temperature applications like exterior coatings.

HPMC's film integrity remains stable under prolonged sunlight due to its ability to reinforce the physical barrier of the coating matrix, though it does not inherently absorb UV radiation.

Hydroxyethyl Cellulose (HEC)

The hydroxyethyl group in the molecular structure of HEC gives it excellent thickening and water retention properties, especially in medium temperature and high humidity environments, making it the material of choice for interior coatings and scenarios that require excellent wet-edge properties. Unlike HPMC, HEC does not form thermogels and may experience viscosity loss at elevated temperatures (>60°C).

HEC has excellent biostability and inhibits mold growth in solution. However, its chemical structure works primarily by reducing the invasiveness of microorganisms into the coating system. Achieving long-term antimicrobial protection with biostability alone is diffcult. Therefore, preservatives (e.g., Kathon, MIT, etc.) need to be added to the coating to build a durable antimicrobial protection system. Studies have shown that HEC is significantly more effective than HPMC in extending the shelf life of coatings when used with preservatives.

Comparison: HPMC vs. HEC: Choose the most suitable for your project

Given their chemical differences, HPMC and HEC display unique advantages and disadvantages in the application to water-based paints, especially under high temperature conditions typical in summer.

1. Performance in High Temperatures

    - HPMC: Exhibits thermogelling behavior at elevated temperatures (50°C–90°C), where it transitions from a solution to a gel, enhancing viscosity and sag resistance in high-heat environments (e.g., exterior coatings applied in summer). Its film integrity remains stable under prolonged sunlight and heat.

    - HEC：Lacks thermal gelling properties and may significantly reduce viscosity at temperatures above 60°C. However, it performs best at medium temperatures (e.g. indoor environments or high humidity scenarios) - not only does it have excellent water retention without thermal degradation, but the high water retention also extends the open time, allowing crews to make long adjustments when rolling or brushing large areas.

2. Application Method and Efficiency

    - HPMC：In high-temperature outdoor applications, HPMC demonstrates exceptional leveling and film-forming efficiency. Its thermogelation property accelerates the drying process while imparting anti-sag performance to summer coatings. Even under direct sunlight, the thermogelation effect ensures rapid film formation, guaranteeing consistent surface quality and enhancing overall film-forming efficiency.

    - HEC：Excels in indoor or moderate-climate applications, providing smooth application and superior water retention for extended open time (e.g., in latex paints). Its thermal sensitivity limits suitability for prolonged exposure to extreme heat.

For more information, please visit MHEC chemical.

Deciding the Right Thickener: Your Paint's Summer Savior

The choice between HPMC (Hydroxypropyl Methyl Cellulose) and HEC (Hydroxyethyl Cellulose) ultimately hinges on the specific requirements and environmental conditions of the coating application.

For outdoor applications or high-temperature summer environments, HPMC is preferred due to its thermogelation property, which enables rapid drying, prevents sagging during application, and ensures stability under elevated temperatures. Its ability to form a gel at moderate-to-high temperatures (50°C–80°C) accelerates film formation, making it ideal for scenarios requiring quick curing and resistance to heat-induced degradation.

Conversely, in indoor or controlled environments with minimal temperature fluctuations, HEC offers distinct advantages. Its superior water-retention capacity prolongs open time for extended application and adjustment during coating, while its chemical structure (when combined with preservatives) reduces microbial accessibility, enhancing formulation stability and inhibiting microbial growth. This makes HEC a better fit for applications prioritizing film-forming consistency and long-term microbial resistance in moderate conditions.

Conclusion

Selecting the right thickener for water-based coatings, especially in summer heat, requires careful consideration of the application scenarios and environmental challenges. JINJI CHEMICAL's HPMC and HEC products offer tailored solutions: HPMC's thermogelation speeds up drying and prevents sagging in high temperatures, ensuring fast film formation outdoors; HEC extends open time with superior water retention and boosts microbial resistance when paired with preservatives, ideal for indoor or controlled environments. By weighing factors like application conditions, film formation, and durability. Choosing JINJI HPMC and HEC ensures your coatings maintain excellent finishes and long-term performance even in harsh summer conditions, safeguarding both visual appeal and functionality.

Coating additives are used in a small amount in coatings, but they can significantly improve the performance of coatings, and have become an indispensable part of coatings. Thickener is a kind of rheological additive, which can not only thicken the coating and prevent sagging during construction, but also endow the coating with excellent mechanical properties and storage stability. It is a very important class of additives for water-based paints with low viscosity.

1 Types of water-based paint thickeners

At present, there are many kinds of thickeners available in the market, mainly including inorganic thickeners, celluloses, polyacrylates and associative polyurethane thickeners. Inorganic thickener is a kind of gel mineral which absorbs water and expands to form thixotropy. There are mainly bentonite, attapulgite, aluminum silicate, etc., among which bentonite is the most commonly used. Cellulosic thickeners have a long history of use and there are many varieties, including methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, etc., which used to be the mainstream of thickeners. The most commonly used of these is hydroxyethyl cellulose. Polyacrylate thickeners can basically be divided into two types: one is water-soluble polyacrylate; the other is homopolymer or copolymer emulsion thickener of acrylic acid and methacrylic acid. It is acidic in itself, and must be neutralized with alkali or ammonia water to pH 8~9 to achieve thickening effect, also known as acrylic acid alkali swelling thickener. Polyurethane thickeners are newly developed associative thickeners in recent years.

2 Characteristics of various thickeners

2.1 Cellulose thickener

Cellulosic thickeners have high thickening efficiency, especially for the thickening of the water phase; they have less restrictions on coating formulations and are widely used; they can be used in a wide range of pH. However, there are disadvantages such as poor leveling, more splashing during roller coating, poor stability, and susceptible to microbial degradation. Because it has low viscosity under high shear and high viscosity under static and low shear, the viscosity increases rapidly after coating, which can prevent sagging, but on the other hand, it causes poor leveling. Studies have shown that as the relative molecular weight of the thickener increases, the spattering of latex paint also increases. Cellulosic thickeners are prone to splashing due to their large relative molecular mass. And because cellulose is more hydrophilic, it will reduce the water resistance of the paint film.

2.2 Acrylic thickener

Polyacrylic acid thickeners have strong thickening and leveling properties, and good biological stability, but are sensitive to pH and have poor water resistance.

2.3 Associative polyurethane thickener

The associative structure of associative polyurethane thickener is destroyed under the action of shear force, and the viscosity decreases. When the shear force disappears, the viscosity can be restored, which can prevent the phenomenon of sag in the construction process. And its viscosity recovery has a certain hysteresis, which is conducive to the leveling of the coating film. The relative molecular mass (thousands to tens of thousands) of polyurethane thickeners is much lower than the relative molecular mass (hundreds of thousands to millions) of the first two types of thickeners, and will not promote splashing. Polyurethane thickener molecules have both hydrophilic and hydrophobic groups, and the hydrophobic groups have a strong affinity with the matrix of the coating film, which can enhance the water resistance of the coating film. Since the latex particles participate in the association, there will be no flocculation, so the coating film can be smooth and have a high gloss. Many properties of associative polyurethane thickeners are superior to other thickeners, but due to its unique micelle thickening mechanism, those components in the coating formulation that affect micelles will inevitably affect the thickening properties. When using this kind of thickener, the influence of various factors on the thickening performance should be fully considered, and the emulsion, defoamer, dispersant, film-forming aid, etc. used in the coating should not be easily replaced.

2.4 Inorganic thickeners

Inorganic thickeners have the advantages of strong thickening, good thixotropy, wide pH range, and good stability. However, since bentonite is an inorganic powder with good light absorption, it can significantly reduce the surface gloss of the coating film and act like a matting agent.

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