Which Wax?

Here we look at the Apiezon Wax products and focus on which wax you might choose for sealing applications.

There are three Apiezon waxes manufactured by M&I Materials Ltd, Wax W, W100 and W40. Each wax is very versatile, finding uses in diverse areas such as sealing joints, mounting substrates and etch resist. Here we focus on which wax is suitable for various sealing applications and how the products differ.

Apiezon Wax can provide an excellent semi-permanent or permanent seal around vacuum joints by melting it and then allowing it to flow it into place. Once the wax cools it will harden to a solid with a very low vapour pressure, providing a seal which is resistant to water and attack from many chemical substances, such as acids. One additional benefit is that if it is necessary to remove the Wax it can be heated up again to remove the bulk and then any residue dissolved using a suitable solvent, such as toluene, xylene or limonene.

So which wax to choose?  Well, primarily the choice comes down to temperature. If you want a solid permanent seal and can handle an application temperature of 130°C then Wax W is the best choice. If this temperature is too high we have another two products which can be applied at lower temperatures and still provide an excellent seal. Wax W100 is the next one in the range. It is a medium hardness wax which will start to melt at 50 to 60°C and has an application temperature of 110°C. This is very handy if you need the vapour pressure characteristics but have heat sensitive components. It is also a little softer than Wax W, so is very good if the joint will be subject to vibration as it provides some damping.

The softest product in the range is Wax W40, this has a melting point of 45°C and is completely liquid at 90°C, so can be melted with hot water to flow into joints and provide a seal.  Wax W40 has a slightly higher vapour pressure than the other two waxes, but is still suitable for vacuums down to below 10^-6 Torr.

There are other ways to apply the Wax products, especially for etch resist and mounting purposes, further information on these is detailed in Apiezon Wax W – the hard one and Wax W100 and W40 – The softer ones or the applications section of the website.