What Is the Densest Rubber?

Rubber comes in many types, each with different properties. When I get asked, “What is the densest rubber?” it’s usually from someone needing a heavy, solid material for specific engineering or industrial uses.

Chlorinated rubber (like chlorobutyl and some FKM grades) and fluorocarbon rubber (FKM, such as Viton®) are among the densest rubbers, with densities often above 1.8 g/cm³. Most standard rubbers like NR, SBR, and NBR have densities around 1.1–1.3 g/cm³.

Understanding rubber density helps in applications where weight, vibration damping, or mass is important—like in high-pressure seals, isolation pads, or counterweights.

What Does “Density” Mean for Rubber?

Density is the mass of rubber per unit volume. It is measured in grams per cubic centimeter (g/cm³) or kilograms per cubic meter (kg/m³). Higher density usually means the rubber is heavier, more solid, and less compressible.

Dense rubbers are often used for damping vibrations, making heavy-duty seals, or where weight adds stability. FKM (Viton®) and other fluorinated rubbers top the list for density.

Typical Densities of Common Rubbers

Here’s a comparison of typical rubber densities:

Why Are FKM and Fluorinated Rubbers So Dense?

FKM and FFKM are packed with heavy atoms like fluorine and chlorine. This gives them not only a high density but also superior chemical and heat resistance.

Their dense structure makes them perfect for demanding sealing applications—high pressure, aggressive chemicals, and extreme environments.

When Is High-Density Rubber Needed?

• For vibration and noise damping (more mass, better energy absorption)
• As high-pressure seals or gaskets¹¹ (less compressible, tighter fit)
• For weights or stability pads (rubber blocks that add mass)
• In aggressive chemical, heat, or oil environments

I always recommend FKM or specialty fluorinated rubbers¹² when the job needs both density and top-level performance.

My Advice on Choosing Dense Rubber

• For most uses, standard rubbers are enough and cost less.
• For heavy-duty, high-heat, or chemical resistance, FKM or FFKM is the go-to.
• Always check the technical data sheet for actual density—fillers and additives can raise the value.

Conclusion

FKM (Viton®) and perfluoroelastomers (FFKM) are the densest common rubbers, with densities near or above 2.0 g/cm³. Choose these when weight, strength, and chemical resistance are critical.