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Let’s Talk Porosity vs. Permeability

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We take our job as the go-to technical experts in custom Green coatings very seriously. That’s why we’re more than happy to answer your questions, no matter how big or how small!

In this week’s blog, we’re exploring the differences between porosity and permeability and how to determine the performance of a given coating. 

Check it out, and let us know what you think!

Question #1: Is porosity the same as permeability?

The short answer is “No” – porosity and permeability are linked but are not the same. Porosity relates to actual pores (or voids) in the structure of a layer or surface, while permeability relates to the ability of a liquid to absorb into a layer or surface. Porosity is a physical phenomenon while permeability is a chemical phenomenon.

Pores do not need to be present for a liquid to permeate into a surface. Solvents can soften and even partially dissolve the resin or polymer content of a layer and absorb into it. Increased porosity is due to both the number of pores per given surface area and/or the size or diameter of the pore present. 

Keep in mind that porosity and permeability relate not only to absorption into a surface but also to the release of a volatile from the surface during drying, curing, and regeneration. For example, a carbon filter that absorbs airborne contaminants.

Question #2: Why is permeability measured by various scales? 

Now that’s a great question! As formulation chemists, often we employ simple, practical means to gain insight into the measurement of permeability. It is common to measure a system via dry times and residual volatile content vs. time vs. temperature. 

Question #3: What does the stability of the coating depend on?

Performance attributes vary within each type of chemistry to a great extent. Manufacturers, such as Van Technologies, formulate coatings to meet certain criteria and put the optimum coating through a number of physical tests to impose stress and strain as well as water and chemical resistance. 

There are a number of industry certifications, including Kitchen Cabinet Manufacturers Association  (KCMA), Window and Door Manufacturers Association (WDMA), Scientific Equipment and Furniture Association (SEFA), and Architectural Woodwork Institute (AWI), that identify testing protocols which coatings must support. 

Although coatings are not certifiable, the surface or component they are applied to are certifiable. Therefore, coatings manufacturers must determine if their respective customers can achieve certification. 

At Van Technologies, we conduct extensive testing to make sure the coatings will perform. Our recommendation is to always look into the details of the coating to make sure it conforms to what you need it to do. Communicate closely with the coatings manufacturer and learn how they test (and certify, if applicable) their coating products.

Remember, the next time you have a coating conundrum, send it our way. We are here to help. 

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