Understanding the Chemical Resistance of Elastomer Gasket Materials29 January 2019
Elastomers are clearly malleable but not flimsy. They’re compressible, not fragile. You see, just because an elastic seal can deform, that doesn’t mean it’s mechanically weak. It’s the same with chemical resistance, a feature elastomer gasket materials possess in abundance. Stretchy cross-linked molecular chains deform and recover while they repel the effects of corrosive chemical attacks. However, to deliver enhanced seal compressibility features, tradeoffs are sometimes made.
A Balanced Set of Gasket Features
By tradeoffs, we’re talking about a loss of one material characteristic while a second property is enhanced. In gasket design, the compressibility factor ranks high, so other design characteristics can fall by the wayside. Well, this design faux pas cannot be permitted, especially on a seal that requires a balanced set of fluid containment attributes. For example, a high level of material compressibility is all very well, but it won’t help if a high temperature weakens the elastomeric bonds. Similarly, a deformable gasket isn’t much good if it lacks an all-important ability to resist harsh chemicals.
Utilizing the Right Elastomer
So the application in question uses high sealing energies, as applied by a series of encircling nuts and bolts, to squeeze an elastomeric gasket. The fluid rushing through the pipes isn’t likely to escape. Looking down the ingredients list of that fluid, however, it contains a corrosive acid. Mechanically sound or not, this caustic chemical will make short work of a seal that doesn’t feature a chemically resistant build. Generally speaking, EPDM and Viton based gaskets provide sound elastomeric resistance. Fluoroelastomers perform well when acids are around. Silicone gaskets, well, they’re more susceptible to acids, but they hold up well when attacked by oils. Likewise, nitrile and neoprene seals remain unaffected when oily substances attack.
Using Chemical Resistance Tables
Complex molecular chains stretch and recover when elastomer gaskets squeeze between two flanges. Importantly, while one part of the chain may stubbornly repel a lubricant or chemical reagent, a second linkage could weaken. Simply put, this is a tricky field of study. Making things worse, there are hundreds of different acids and oils, which will affect different gasket materials in different ways. To determine those effects, we need a chemical resistance table, a datasheet that contains a list of hundreds of chemicals. Running a finger down the table column, we can see how any single chemical will impact a chosen elastomer.
Elastomer science is ruled by hundreds of advanced bonding conventions. Cross-linked and deform-capable, the malleable materials react according to seemingly unfathomable physical laws. Check a gasket datasheet to see if it’s specced as a chemically resistant material. Which oils or acids does it specifically repel? For more information, contact the gasket manufacturer or grab a copy of a chemical resistance table.
Optimized by: Netwizard SEO