What is the Difference Between MHEC and HPMC?

In construction and industrial applications, cellulose ethers are an important class of chemicals used in a wide variety of products.

When it comes to cellulose ethers, Hydroxypropyl Methylcellulose (HPMC) and Methyl Hydroxyethyl Cellulose (MHEC) are two of the most common cellulose derivatives.

They are both water-soluble, non-toxic, and offer a wide variety of useful applications to construction, pharmaceutical, cosmetics, food and various other industries.

However, although they have commonalities, they also have different chemical properties and different applications. So, what is the difference between MHEC and HPMC?

This article will examine the structural differences, properties, and applications of both, so we can better understand when and why to use each.

What is HPMC?

Hydroxypropyl Methylcellulose (HPMC) is a non-ionic cellulose ether, derived from natural materials such as wood pulp or cotton. It is modified by reacting cellulose with propylene oxide and then with methyl chloride.

When the reaction is complete, HPMC is a powder that is soluble in cold water. HPMC has various applications across many industries, but is most commonly used in construction.

HPMC has various properties that make HPMC very useful:

Water retention: HPMC helps retain water in construction products such as plaster and cement that improve workability and limit cracking.

Viscosity control: It serves to thicken, producing viscosity in products like adhesives, paints, and coatings.

Film formation: It has a flexible film forming ability upon application to a surface; creating a more durable and stronger material.

Better adhesion: HPMC is often used in tile adhesives, creating a bond between tile and setting substrate.

With the properties of HPMC, it is often utilized in applications like:

• Tile adhesives and grouts.
• Cement and mortar products.
• Plasters and coatings.
• Pharmaceuticals (as a binder in tablet)
• Cosmetics (as a thickener in lotions and creams)

What is MHEC?

Methyl Hydroxyethyl Cellulose (MHEC) is another cellulose ether that is very similar to HPMC, but with a different set of chemical modifications. MHEC is made by modifying cellulose with methyl chloride and ethylene oxide. MHEC will introduce both methyl groups and hydroxyethyl groups into the cellulose structure.

MHEC contains many of the same properties as HPMC with its water-soluble, thickening capacity. However, MHEC includes hydroxyethyl as one of the groups that confer some distinct benefits in some applications.

Some properties of MHEC are:

Higher water retention: MHEC has a higher retention of water than HPMC and can be especially useful in moisture critical environments.

Increased flexibility: The hydroxyethyl group provides more flexibility, which can be an advantage in applications such as coatings, where it is valueable to have some elasticity.

Improved rheological properties: MHEC can perform better in flow behavior, particularly in high-viscosity applications.

Uniting heat stability: MHEC can present a better resistance to heat than HPMC. This is benficial in certain industrial environments.

MHEC would typically be used, responsible for the functional actions of (within)

• Tile adhesives and grouts (specifically in flexible formulations)
• Construction mortars (to increase the rigidity of the bond and degree of watertightness)
• Painting and coatings (to improve the formulation’s texture and stability)
• Oilfield (as a thickening agent – an addition of either rearriage in drilling fluids)
• Pharmaceuticals and food products (as a thicker stabiliser)

Key Differences Between MHEC and HPMC:

MHEC and HPMC are cellulose derivatives with a lot of similar functionalities, but there are differences in their chemical structure, properties and their uses. Here are the key differences:

1. Chemical Structure

HPMC: HPMC contains both hydroxypropyl and methyl groups. The combination of these two groups enhances the solubility of HPMC in water, and also provides good film-forming properties. HPMC is optimum for applications where there is an extra solidity of bond required.

MHEC: Contains methyl and hydroxyethyl groups which gives it a different chemical behavior. The hydroxyethyl group significantly adds to the material’s water-holding capabilities and adds flexibility, which is beneficial for applications that allow flexibility in use, such as flexible adhesives and mortars.

2. Water Retention and Solubility:

HPMC: HPMC retains water, it is very good at it, but MHEC still retains a little more water. HPMC may have lower overall water retention because the hydroxyethyl group in MHEC is better for grabbing water molecules.

MHEC: MHEC, on the other hand, will generally have better water retention because there is a hydroxyethyl group, which makes MHEC better at handling high-moisture applications or products that are designed with a longer working time in mind, like tile adhesives and construction mortars.

3. Viscosity and Flow Behavior:

HPMC: HPMC is a great thickener and provides viscosity control, but it can be too stiff as an additive for applications requiring flexibility or ease of flow. HPMC is effective in product types, such as coatings and adhesives.

MHEC: MHEC typically demonstrates better flow properties, though especially in high viscosity formulations. Consequently, MHEC is often the better choice in applications where smoothness and evenness is more vital. MHEC is also typically better at improving flow characteristics in products over the shear of the application.

4. Flexibility and Elasticity

HPMC: HPMC can flex somewhat but is more rigid than MHEC is, which could be a disadvantage in applications such as coatings or flexible adhesives, where the material has to bend or stretch, it should do so without cracking.

MHEC: The hydroxyethyl group in MHEC allows for more flexibility, and therefore makes it a better choice for applications in needing to stretch, such as flexible tile adhesives or coatings, and even certain sealants.

5. Thermal Stability

HPMC: HPMC has generally good thermal stability, but will degrade at higher temperatures. This may be of concern in certain applications in the industrial setting requiring high heat stability.

MHEC: MHEC is usually more thermally stable than HPMC, making it the better choice for applications that will be exposed to heat or fluctuating temperatures, like the manufacturing of coatings, or construction materials for use in extreme conditions.

Applications and Usage

HPMC: HPMC is mainly used in construction materials such as tile adhesives, cement-based mortars and plasters because of their ability to film form and improve adhesion. HPMC is also found in pharmaceuticals and cosmetics as a binder, thickener and stabilizer.

MHEC: When applications require a high degree of water retention like in construction adhesives, oilfield, or specific types of paint and coatings, MHEC is often the choice and desired.

In the case of MHEC, it provides high viscosity, water retention properties, and the flexibility to be drawn and dried successfully.

Conclusion

The difference between MHEC and HPMC for manufacturers is that they differ chemically on a structural level, perform differently with water retention, control viscosity, demonstrate more elongation potential with flexibility, and finally, their thermal stability is different with MHEC is substantially more stable.

Ultimately, the choice ought to be influenced by the need for either high water retention, flexibility, or thermal stability, depending on the needs of the product.

When producers fully understand the differences between these cellulose ethers, they can produce or build more efficiently with the intended performance and durability.

Both MHEC and HPMC provide product value for any industry, whether construction, painting, coatings, or pharmaceutical. Each had its own value characteristics to help balance the overall product performance.