| Property | Value |
|---|---|
| Temperature range | -50 °C to +80 °C |
| Hardness | 30–90 Shore A |
| Best at | Tensile, tear, fatigue life, resilience |
| Contains fluorine | No |
Why it still wins on dynamic parts
A mount or bushing does not fail from chemical attack. It fails from millions of load cycles, and natural rubber survives more of them than anything else we can mix. Its resilience is high, meaning it returns energy rather than converting it to heat, so a natural rubber part running at frequency stays cooler than a synthetic one doing the same work. Cooler parts last longer. That compounding effect is why natural rubber is still specified for bridge bearings and engine mounts sixty years after synthetics were supposed to replace it.
It also builds strength without reinforcing filler, because it crystallises under strain. A gum natural compound can hit tensile numbers that a synthetic needs a heavy carbon black loading to approach, and heavy filler loading costs you fatigue life. This is the one family where the strongest compound is not the most filled one.
How we compound and test it
Natural rubber is sulfur-cured, and the sulfur-to-accelerator ratio is where the tradeoff lives. A conventional cure gives the best fatigue and tear; an efficient cure gives better heat aging and lower compression set but gives up some flex life. We pick that based on whether the part is dynamic or static.
Antiozonant and antioxidant packages are not optional here, they are the part of the formulation that decides whether the compound survives a shelf and a service life. We run ozone exposure and heat aging in the lab rather than trusting a supplier data sheet, because the protective package interacts with the cure system and the filler.
The two mistakes buyers make
The first is using it outdoors without asking. Unprotected natural rubber cracks in ozone at concentrations you cannot smell, and a part that looked fine at install fails in eighteen months in a parking lot. If the part sees weather, either the antiozonant package has to be designed for it or the family is wrong.
The second is specifying it near oil. Natural rubber swells badly in petroleum products. A mount that is perfect in every mechanical respect will turn to mush if it sits under a slow drip from a fitting above it. We ask about incidental oil exposure on every natural rubber quote, because the answer changes the material.
Typical uses
- Engine and equipment mounts, bushings, and isolators
- Bridge and structural bearings
- Springs and shock absorbers
- High-fatigue dynamic parts indoors or shielded from weather
- Bonded metal assemblies where flex life governs