During the past weeks, I have read countless post about the humidity level in dry boxes, and I am myself also not sure anymore what is the truth, what is imagination, an what is a typical urban myth. So, I call up the head of material research from one of my clients, to have chat with him. This company ( do not want to post the name here) , is a world market leader in silicones and elastomers, as well as high tech lubricants.
I asked some very simple questions, and would like to share the answers here.
1) Does the humidity effect the degeneration of rubber ?
Yes, but it has a rather small impact. Also, it depends on the type of rubber material. Some rubbers degenerate faster in high humidity, some in low humidity.
2) So, what has a high impact on rubber degeneration ?
4 major factors
1) High temperature. The higher the temperature is, the faster the rubber degenerates. This effect is exponential, means it gets much stronger with higher temperatures. The starting point is about 18 degrees celsius. ( rubber can also be stressed at extreme low sub zero temperatures, but that is a different effect)
2) UV light. Almost all rubber materials, synthetic and natural, age much faster under UV light.
3) Mechanical stress. Constant movement or tension leads to a faster degeneration of rubber materials
4) Oxygen. The higher the oxygen content in the environment is , the faster is the degeneration.
3) Do lubricants dry out in low humidity
No. Modern synthetic technical lubricants ( different form medical lubricants) are not water based, the ingredients are not water-soluble. The level of humidity has hardly any impact on the evaporation of the volatile ingredients.
So,what has an impact on lubricants.
Temperature has a rather big impact on lubricants (but most modern lubricants are not effected by room temperature), and so has dirt and dust. Contamination (Microscopic dust particles) probably has the biggest impact on technical lubricants which are used in room temperature.