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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
MATERIAL
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