ASTM D 1418 Designation: NR

ASTM D 2000, SAE J200 Type / Class: AA

STANDARD COLOR: Black

TRADE NAMES: Too numerous to list.

RELATIVE COST: Low

GENERAL TEMPERATURE RANGE: -60° to +220° F

Polyisoprene vulcanized from the latex of the Hevea brasiliensis tree, natural rubber was the sole O-ring polymer before the development of synthetic elastomers in the 1930s. Though its use has since sharply declined, natural rubber offers many excellent characteristics, including low heat build up, high resilience and elongation, good abrasion resistance, and low temperature flexibility.

Natural rubber has both high tensile strength and good tear strength due to its tendency to strain crystallize. It also undergoes low compression set. Its chief drawback is its poor resistance to either oils or solvents. The double bond in its main polymer chain (see Figure 41) also makes natural rubber susceptible to attack by oxygen, ozone, and UV light.

NR PERFORMS WELL IN:
• Alcohols
• Organic acids
• and as non-hydraulic seals

NR DOES NOT PERFORM WELL IN:
• Aromatic, aliphatic, or halogenated hydrocarbons
• Ozone
• Petroleum oils

“Natural rubber was the sole O-ring polymer before the development of synthetic elastomers in the 1930s.”

Figure 41