Natural Rubber (NR)
Description:
Natural rubber is primarily produced from the latex of the Hevea tree, and the chemical name of this polymer is polyisoprene. Natural rubber possesses many excellent physical properties including high resilience, high tensile strength, good abrasion resistance, and is extremely waterproof.
Common Uses:
Natural rubber is found in:
- Dampeners
- Tires
- Electrical components
- Rubber gaskets and seals
- Rubber hose and tubing
Properties:
Standard Compound: -50°C (-58°F) to 70°C (158°F)
Hardness: 40 to 90 Shore A
ASTM D1418 Designation: NR
ASTM D2000 Designation: AA
Standard Colors: Black
Optional Colors:
Production:
Natural rubber compounds are sulfur cured, and are usually mixed with SBR and BR for use in the production of tires.
Advantages:
Natural rubber performs well in alcohols and organic acids.
Limitations:
Natural rubber suffers from poor resistance to hydrocarbon oil. It is not suitable in UV, oxygen, and ozone because of the double bond in the polymer backbone. However, its poor weathering resistance can be improved with special additives. NR is often vulcanized to improve resistance and elasticity, and to prevent it from perishing.
Exposure to natural latex rubber products, such as latex gloves, can cause anaphylactic shock and other allergic reactions which has influenced the medical industry to move away from the use of natural rubber.
Frequently Asked Questions About Natural Rubber (NR)
What is Natural Rubber (NR)?
Natural Rubber is a polymer known as polyisoprene, derived mainly from the latex of the Hevea tree. It is valued for its high resilience, tensile strength, and excellent waterproof properties.
What are the main applications of Natural Rubber?
NR is commonly used in dampeners, tires, electrical components, gaskets, seals, hoses, and tubing due to its toughness and flexibility.
What temperature range can Natural Rubber withstand?
The standard operating temperature range for NR compounds is approximately -50°C (-58°F) to 70°C (158°F), depending on formulation and curing.
What are the hardness levels available for NR?
Natural Rubber compounds typically range from 40 to 90 Shore A, allowing engineers to select the right hardness for their specific application.
How is Natural Rubber produced and cured?
NR is sulfur-cured and often blended with SBR (styrene-butadiene rubber) and BR (butadiene rubber) to enhance durability, especially in tire production.
What are the key advantages of Natural Rubber?
It offers superior elasticity, excellent tensile strength, and good resistance to alcohols and organic acids.
What are the main limitations of Natural Rubber?
NR has poor resistance to hydrocarbon oils, ozone, UV, and oxygen. Without additives or protective coating, it degrades when exposed to weathering.
Can weathering resistance be improved in NR?
Yes. The addition of stabilizers, antioxidants, or protective coatings can significantly enhance NR’s resistance to ozone, sunlight, and oxygen.
Why is Natural Rubber vulcanized?
Vulcanization improves elasticity, mechanical strength, and prevents the rubber from becoming brittle or deteriorating over time.
Can Natural Rubber cause allergic reactions?
Yes. Some individuals are allergic to natural latex proteins, which can cause severe reactions, including anaphylaxis. This has led the medical industry to shift toward synthetic alternatives.