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The Difference Between High and Low Modulus Sealant 

 April 29, 2021

By  Dale Keese

Silicone sealants work as an adhesive, usually for creating airtight seals between two surfaces on a joint. It’s also referred to as caulk or silicone glue, and they are categorized as either high or low modulus sealant. However, many people aren’t sure what the difference is between the two.

High or low modulus silicone sealant refers to the tensile strength of the silicone. High modulus sealants typically contain fungicide, and are used on interior joints in damp areas such as the bathroom, while low modulus sealant is used outside in expansion joints that require more movement.

When deciding what sealant works best for your needs, there are some things to think about. Read on to learn more about the differences between low modulus vs. high modulus sealant.

Shopping for a silicone sealant can easily get overwhelming because of all the different options available out there. However, getting to know more about the various types will help you make an informed decision about the right one that you need.

The reason there are so many silicone sealant varieties is because each of them has a specific purpose and use. That’s why it isn’t advisable to go to your nearest DIY shop and grab the cheapest one you see. Also, keep in mind that not one silicone sealant can be used for every single job; they differ according to resistance, durability, and flexibility.

The most common uses for high modulus and low modulus silicone sealants are in window and door seals, sealing or edging showers and baths, fridge seals, plumbing joints, joint protection, wire entry seals, and electrical repair. They are also preferred compared to other kinds of sealants because they possess numerous desirable characteristics including temperature and UV resistance, they last longer, and they have the highest movement capability of all.

The main difference between high and low modulus sealant is that a high modulus sealant finishes rigidly, and many of them contain fungicide which make them ideal for use in damp-prone environments. They are also more hard-wearing, making them ideal for use in sinks, showers, baths, kitchen worktops, and other similar locations. They are also beneficial for sanitary and internal uses.

On the other hand, a low modulus sealant has better movement and elasticity. They more adhesive and long-lasting. For these reasons, it’s better for use in glass wall assemblies and perimeter seals.

When you’re thinking about the modulus that best suits the application at hand, think about the movement characteristics of the surface.

Here’s a breakdown of each of them:

High modulus silicone sealant:

  • Reduced stretch
  • Rigid and hard-wearing

Low modulus silicone sealant:

  • High stretch capability
  • Strong adhesion
  • Enables more movement
  • Lasts longer

These silicone sealants can be further broken down into other types:

Low modulus acetoxy sealants: These are stretchy, acid-based products that are widely used as an all-arounder because they are appropriate for many types of jobs. They are also more affordable, making them the sealant of choice for sanitary purposes, interior and exterior glazing, general building use, or adhering building surfaces.

Low modulus neutral sealants: These are ideal for sealing windows and door frames. They are stretchy and adhesive, but also last longer than low modulus acetoxy sealants.

High modulus acetoxy sealants: These are used for kitchen and sanitary purposes. Most formulations include fungicides which is useful for preventing microorganisms.

Medium modulus sealants: These are another general-purpose type of sealant that is used for accommodating movements without putting too much stress on the sealant.

How to Choose Between Low Modulus and High Modulus Sealant

Movement: Movement capability is determined by how much percentage a joint width can accommodate; for example, a sealant with more or less 10% movement for a 25mm. joint means it can stretch to as large as 28mm, or shrink to 23mm without destroying the sealant.

Exposure resistance: High-performance silicone sealants are those that can remain flexible despite exposure to the sun, extreme temperatures, and moisture.

Hardness: Harder sealants are less prone to damage. However, it should also be considered that the harder the sealant, the flexibility will also decrease.

VOC content: Volatile organic compounds (VOC) vary from one product to the other. Most sealants these days have low VOC levels, though generally speaking, solvent-based silicone sealants contain more VOC’s which means they have higher levels of environmental toxins and respiratory irritants.

Cost: Just like with any product, just because a high modulus or low modulus silicone sealant is cheaper does not mean that it’s more effective. Pricier products are usually better when it comes to performance and quality. Keep in mind that it costs more to replace a failed sealant than it is to use the correct one from the start.

What Is The Best Low Modulus Sealant?

There are several great quality low modulus sealants in the market. They’re available on Amazon and can be delivered right to your doorstep too:

-   Dow Corning Clear Multi-Purpose Sealant
-   Rutland Silicone Sealant
-   GE Sealants & Adhesives Advanced Silicone Window & Door Sealant

What Is The Best Medium Modulus Sealant?

Check out these examples of medium modulus silicone sealants available online:

-   Spectrem 2
-   Tremsil 400

What Is The Best High Modulus Sealant?

Here are some examples of high modulus silicone sealants that you can find online:

-   Arbo Arbomeric MP20 Sealant
-   Dowsil Sanitary Acetoxy Silicone
-   Everbuild Aqua Mate Sealant

About the author

Hey, I'm Dale Keese.. thanks for reading.. hopefully this article can save you some time and trouble with your sealing job. I'm also in the process of making some video walk-throughs for youtube so check back soon! thanks

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