Natural Rubber

Natural Rubber Tree Tapping

Natural rubber is the only non-synthetic rubber. It is a natural resource obtained from latex found in the sap of Hevea Brasiliensis trees. Natural rubber has the highest resilience of all rubbers and a low level of heat generation.

A special feature of natural rubber is that at high levels of stress, the rubber becomes very tough. As the natural rubber is stretched the amorphous polymers slip over each other and become aligned and partially crystalline. Strength is added in the direction of the polymer chains. This is called “Stress Crystallization” and makes the natural rubber very resistant to tear.

Key Properties of Natural Rubber:

  • Fully biodegradable.
  • Large deformation capacity meaning that the material can be repeatedly loaded and unloaded.
  • Strain induced crystallinity – added strength when deformed.
  • Good tear strength.
  • High resilience.
  • Good flex fatigue and resistance.
  • Good set and creep resistance.
  • Good adhesion.

Drawbacks:

  • Must be masticated - extra stage of processing.

Chemical Compatibility:

  • Can be used with water and some dilute acids, alkalis, and chemicals.
  • Not suitable for applications with petroleum-based oils and fuels, greases, and non-polar solvents.
  • Susceptible to attack by oxygen, ozone, and UV. This effect can be minimized through the formulation of the compound.

Operating Temperature Range: -50 to + 80 °C

Typical Applications:

  • Engine mountings.
  • Truck tyres.
  • Anit-vibration mounts.
  • Drive couplings.
  • Haul-off pads.
  • Isolators (earthquake pads).
  • Bearings.
  • Springs.

Latex Natural Rubber

High strength and elasticity make this a good material choice for thin, strong products.

Drawbacks:

  • Can cause allergic reactions.

Typical Applications:

  • Adhesives
  • Carpet backings
  • Rubber gloves
  • Condoms
  • Medical devices
  • Bungee cord
  • Sheeting

Polyisoprene (IR)

Polyisoprene (IR) is a synthetically made rubber which is designed to replicate natural rubber. Polyisoprene has the same chemical structure as natural rubber and offers comparable material properties. However, polyisoprene does have a slightly decreased tensile strength, tear strength and elasticity. Natural rubber is normally less pure than polyisoprene and may still contain latex proteins.

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