Some applications call for the blocking of liquids and gases, particularly applications that need foam for gasketing, which is why the best types of foam for gasketing have low permeability. What is permeability in terms of foam? Which types of foam should you be using for these types of applications?
This is what you need to know about permeability in foam.
What is Permeability?
Permeability is a material’s ability to allow liquids or gases to pass through it. The materials generally have pores that allow for liquid and gas permeability. The wider the pores (or higher quantity) are, the more permeable the material will be.
What are Low Permeability Foams?
Low permeability foams block liquid or fluid penetration. They are foams (usually used in gasketing applications, that are generally closed cell, enabling them to block liquids and/gases from passing through them.
High permeability foams, on the other hand, are often used in filtration applications because they allow water and gases to permeate through the material.
The level of permeation in a foam greatly changes its uses and applications. Some applications call for foam that allows for air/gas permeation while blocking the flow of water. Other applications call for foams that allow both water and gases to flow freely. The type of filtration and gasketing needs of each application will call for foams with different levels of permeability.
The Difference in Permeability of Open and Closed Cell Foams
Open cell foam is primarily made up of cells that aren’t fully encapsulated, meaning that the cell walls are deliberately left open in order to allow gas and water to flow through them. This makes open cell foams more permeable than closed cell foams. However, some open cell foams are also better at absorbing water than closed cell foams, meaning that the material can degrade when exposed to water and moisture (a process known as hydrolysis). This is not the case for all open cell foams, but it’s something to keep in mind when choosing a foam for your application.
Closed cell foams are made up of cells that are closed off and encapsulated. This makes the foam less permeable and breathable. While closed cell foams are better known for gasketing applications rather than filtration, there are variations that allow for an appropriate level of permeability.
For more on the difference between open cell and closed cell foam, read this quick guide.
Types of Low Permeability Foam
Low permeability foams are mostly used in gasketing applications. These types of foams can include:
- Vinyl Nitrile Foam
- High-Density Polyurethane Foam Grade
- Neoprene Blend Foam
- Ether-based polyurethane Foams
- Some Silicone Foams
Need help choosing a low permeability foam for gasketing or filtration application? Get in touch with the foam experts at Amcon today!.