When selecting a sealant, understanding the difference between low modulus and high modulus options is crucial. These terms refer to the flexibility and elasticity of the sealant – key factors in determining how well it performs in different applications. Elastic modulus measures the resistance of the sealant being deformed elastically when a force is applied to it. Put simply, a low modulus (LM) silicone sealant offers less resistance to being stretched than a high modulus (HM) silicone sealant.
At Hodgson Sealants, we offer a wide range of both high and low modulus sealants, each formulated to meet specific needs. But what exactly is a low modulus sealant, and how does it compare to a high modulus alternative? Let’s break it down.
What is a low modulus sealant?
A low modulus sealant is designed to be highly flexible, offering low resistance to deformation and stretching. This means it can elongate and compress significantly without cracking or losing adhesion. Typically, these sealants can accommodate movement up to 25-50% of their original composition and return to shape without damage, making them ideal for applications where movement is expected.
Because of their flexibility, low modulus sealants exert minimal stress on bonded surfaces, reducing the risk of damage to the substrate as materials expand and contract.
Our Silfix U9 sealant is one of the best low modulus silicone sealants available, offering superior adhesion across a wide range of surfaces. It accommodates significant movement, performs well at various temperatures, and is even suitable for use with laminated glass.
Where are low modulus sealants used?
Low modulus sealants are ideal for applications where joints experience frequent movement, such as:
- Building facades and curtain walls – Sealing gaps between glass, metal and masonry.
- Windows and door frames – Preventing air and water ingress while allowing natural expansion and contraction.
- Roofing and cladding systems – Withstanding temperature-induced material shifts.
- Bridges, pavements and parking structures – Providing flexibility in areas exposed to constant motion and environmental stress.
How do low modulus sealants differ from high modulus sealants?
While low modulus sealants are highly flexible, high modulus sealants are stiffer and offer more resistance to movement. Here’s a closer comparison:
| Feature | Low Modulus sealants | High Modulus sealants |
| Flexibility | Highly flexible, accommodates significant movement (25-50%) | Rigid, handles minimal movement (10-25%) |
| Stress on substrate | Minimal, reduces risk of damage | Higher, may cause cracking if joint moves too much |
| Durability | Softer, more prone to mechanical damage | Harder, more resistant to abrasions |
| Weather resistance | Excellent UV and weather resistance | Suitable for interior or protected environments |
Because of their flexibility, low modulus sealants are ideal for exterior applications, where they can accommodate natural building movement caused by temperature changes and environmental exposure. High modulus sealants, on the other hand, are better suited for static applications where strength and durability are key concerns.
Choosing the right sealant for your project
Selecting the right sealant depends on the movement expected in the joint, the materials being bonded and the environmental conditions. If flexibility and movement tolerance are essential, a low modulus sealant is the best choice. However, if a stronger, more rigid bond is needed in a low-movement area, a high modulus sealant is preferable.
At Hodgson Sealants, we supply a variety of sealants tailored for different applications, ensuring you get the best performance for your project.
For more information on our range of high and low modulus sealants, contact our sales team today.
