When choosing rubber gasket material it’s important to consider chemical compatibility. What’s sometimes overlooked though is that compatibility relates to more than just the fluid being sealed. Cleaning agents and solvents that will come into contact with the sealing material must also be considered.

One widely used cleaner/solvent is acetone. While compatible with some types of rubber, it reacts negatively with others. Here’s what to consider.

Acetone Exposure

Although perhaps best known as a nail polish remover, acetone has many other uses. It’s a key ingredient in lacquers used in the automotive and furniture industries, it’s used in some textile manufacturing, and it’s an industrial cleaner, particularly in the printed circuit board sector.

Chemists classify acetone as a ketone. It’s generally harmless to humans, although is very flammable. However, it will damage some types of rubber.

Rubber Takes Many Forms

In its original sense, “rubber” refers to an elastic material made from the sap of the rubber tree. Today though it’s often used as a general term for almost any elastomeric material.

The closest materials to natural rubber are SBR or red rubber, and NBR, also known as nitrile and Buna-N. (These were originally developed as synthetic forms of natural rubber.) Then there are other elastomers like neoprene, EPDM, silicon and FKM/Viton® that behave in similar, often superior, ways to natural rubber. All these are sometimes lumped under the heading of “rubber”. This causes a problem because they react differently to chemicals like acetone.

Positive and Negative Compatibility

The good news is that acetone won’t react with or degrade EPDM. Unfortunately it reacts negatively with many other rubber-like gasket materials.

With natural rubber, SBR and neoprene, the degradation is minimal: brief exposure is unlikely to cause any problems. However, in NBR and FKM/Viton it causes swelling which can quickly lead to failure of the seal. For this reason these types of rubber are best kept away from acetone.

If in Doubt, Ask an Expert

Material compatibility is an important part of gasket material selection. If you have any concerns, contact us and speak with a specialist.

Used on its own or blended with rubber, cork makes an excellent gasket material. It’s flexible over a wide temperature range and very compressible. It resists oil, it’s fire-resistant and it doesn’t creep. Why then, do some gasket and gasket material buyers express concern when presented with it?

The answer is, in some quarters there’s a perception that cork absorbs water.  Does cork absorb water is a frequently asked question.  If this were true, wine bottles would leak when laid horizontally, but it’s not entirely incorrect either. For an explanation, let’s delve into the properties of this natural material.

The Structure of Cork

Cork grows on trees, and like all biological materials, is composed of cells. As a paper from North Carolina State University (NCSU) noted in 2015, the cells in cork contain air, so it can be considered a closed cell foam. (“The rationale behind cork properties: A review of structure and chemistry” Pereira, H. (2015).)

This similarity to a sponge material is probably the origin of the belief that it absorbs water, but there’s a bit more to it. The NCSU paper notes that, “The porosity coefficients of cork range from below 2% to over 15%”. Or in other words, it will absorb a little water. This occurs at the cells that have been cut open on the surface and also through defects in the cell structures.

Countering this though, the cell walls are made mostly of a substance called suberin. Naturally hydrophobic, this repels water, which works against absorption.

So, as a conclusion, yes, cork can absorb water, but the amount is very small. It’s not a sponge.

Relevance to Gasket Materials

Natural cork, often described as composition cork, can be used for gaskets. More often, it’s blended with a synthetic rubber like neoprene, nitrile or silicone. This increases strength and flexibility while enhancing oil resistance.

Thanks to high compressibility, cork-rubber blend gasket material works well on uneven surfaces and in low pressure applications. It’s available in thicknesses from 1/32” to ¼”, can be die, water jet or laser cut to shape, and no, it won’t absorb water – to any significant degree.