Outgassing

How to overcome the consequences of Outgassing

Outgassing is defined as “the release of a gas that was dissolved, trapped, frozen, absorbed or adsorbed in some materials’’.

Parts of rubber formulation, decomposition products of the ingredients or other gasses trapped in the polymer composition during the moulding process can turn unstable and be released under vacuum conditions.

Visual Indications and Description

Thin film settled on surrounding surfaces, decrease in cross-sectional size, other components may demonstrate some level of weight loss by means of water vapour that can be contaminant in several installations. In extreme cases, shrinkage can be noticed.

Contributing Factors

Inadequate cure of the seal, low hardness seal, plasticized seal, high vacuum levels.

Suggested Solution

Make sure the seal is adequately post-cured, avoid plasticized elastomers, use materials with a pure polymer, and use materials for the correct temperature.

Though this process is unavoidable, it is accelerated at raised temperatures and in high vacuum circumstances. Electrical contact and optical installations are a big concern in this situation because they comprise sensitive surfaces that must stay uncontaminated.

A process called post curing of a rubber element such as Silicone (VMQ), Fluorosilicone (FVMQ), or Viton® (FKM/FPM) prior to assembly removes a lot of undesirable contaminants and enhances physical features by advancing the level of crosslinking.

Post curing removes contaminants by evaporation and diffusion, executed at a temperature higher than the service temperature of the element. Once the contaminants are vaporized, they’re no longer there to outgas.

Inadequate or poor post cure can reduce element’s elasticity, strength, and compression set features as well as cause chemical decomposition, bubbling, and unsightly sticky surface deposits.

Elastomers such as Nitrile (NBR) and Natural Rubber don’t benefit from this process as much as above-mentioned rubbers.

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E & OE. M Barnwell Services endeavours to make sure all the content is correct. Information has been gained from manufacturing partners.