Natural Rubber: Material Basics, History, and Fun Facts
- By Lee Lechner
- Jul 26, 2022
What Is Natural Rubber?
Natural rubber is "an elastic material obtained from the latex sap of trees that can be vulcanized and finished into a variety of products" (source). Natural rubber is an elastomer or an elastic hydrocarbon polymer with the unique quality of bouncing back to its normal shape after it is stretched, making natural rubber elastic and stretchy.
The basis of all natural rubber is latex, which is a soft white substance harvested from specific trees. Most of the world’s latex comes from the Hevea brasiliensis tree, which we'll discuss next.
Where Does Natural Rubber Come From?
Hevea brasiliensis is most commonly known as the "rubber tree." This tree can grow up to around 141ft (43m) in the wild, but the ones cultivated on plantations are usually much smaller, as tapping the latex out of the tree restricts its growth. The trees are typically cut down after 30 years due to a decline in latex production from trees as they age. When cut down, the wood is harvested and used for furniture production.
Rubber trees are native to the rainforests in the Amazon region of South America, which includes Brazil, Venezuela, Ecuador, Columbia, Peru, and Bolivia. Most commercially-produced natural rubber is grown in Southeast Asia, mainly in Thailand and Indonesia.
Rubber Tapping Process
The rubber tapping process is how latex is collected from rubber trees. This process starts with slicing a groove into the tree's bark approximately 1/4" deep using a hooked knife and then peeling the bark back.
Rubber tappers will remove a thin layer of bark from the tree trunk every night, yielding latex for up to five hours. This is typically done at night or early in the morning before the temperature rise's to ensure the latex drip longer before sealing up the cut.
How is Natural Rubber Made?
Processing
Once the latex has been gathered from the trees, ammonia will typically be added to prevent the sap from solidifying. In a process called "coagulation," acid is added to the mix to extract the rubber. This process takes approximately 12 hours. Once that is done, the mixture will be passed through rollers to remove all the excess water and then hung to dry for several days.
Once dry, the rubber is sent to processing. In this stage, chemicals are added to the rubber to stabilize it. Without this step, the rubber becomes brittle when cold and sticky when warm/hot.
Vulcanization
Finally, the natural rubber goes through a heat-treatment phase called "vulcanization" to make the rubber strong and durable. During this stage, the material is cooked (typically with sulfur) to create extra bonds or cross-links between the rubber molecules to ensure they don't fall apart easily.
Once vulcanization is completed, imperfections are removed from the rubber, and the material is ready to be shaped or molded into its final product.
Natural Rubber Fun Facts
Rubber may not be the peak of exciting topics to research, but what happens if a question pops up during your next venture at the local bar trivia night? Will you be ready? Probably not! So, we compiled a list of some more interesting facts about natural rubbers that you may or may not know.
- Rubber was first known to be used by natives of Central America around 1600 BC. They used rubber to make rubber balls and boots.
- Around 20,000 species of plants produce latex, but only about 2,500 of them have been found to contain rubber in their latex.
- One of the biological functions of rubber in plants is to help them heal after they are damaged by covering wounds to help stop the bleeding.
- Japan occupied rubber tree plantations in Southeast Asia during World War II, restricting rubber exportation. This resulted in several countries researching the creation of artificial rubber that would be used on the tires of many vehicles made during the war.
- Rubber trees produce latex material when they are "wounded."
- The Mayans referred to rubber as "Kik," which meant blood, and the natives of Mexico called it "Olli" or "Castillo"
- Using rubber as an eraser was an accidental discovery in 1770 when Joseph Priestly discovered that he could rub away pencil marks using natural rubber
- Thailand and Indonesia supply more than 60% of the world's natural rubber
- Approximately 50% of the global natural rubber goes to manufacturing tires
Common Uses for Natural Rubber
Natural rubber may not be as significantly used as synthetic rubbers, but that doesn't mean you're not using any in your everyday life! Below we've listed some of the most common products made using natural rubbers.
- Automotive Applications: Gaskets, Seals, Vibration Isolators, Tires (made of 50% natural rubber), Bumpers, Shock Mounts (Excellent ability to absorb vibration and shock)
- Pencil Erasers
- Surgical gloves
- Clothing: Natural rubber in its fibrous form is elastic, giving clothing manufacturers the ability to make tight-fitting, stretchable clothing
- Flooring: Commonly used for flooring in gyms, commercial kitchens, animal shelters, and even playgrounds as it offers padding that helps prevent fatigue and is waterproof, slip-resistant, and durable.
Conclusion
The process of developing natural rubber is a fairly straightforward process with an exciting history. From erasers to automotive tires, natural rubbers still play a significant role in several products you probably use daily. What will be interesting to pay attention to over the coming years is what alternative sources of latex will be used to meet global demand.
We hope you enjoyed this post! Be sure to subscribe below as we continue this series by covering synthetic rubbers and how they differ from natural rubbers in future posts.
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What is Synthetic Rubber & How is it Made?
Synthetic rubber is any MAN-MADE elastomer that is made by linking polymer molecules together.
REWRITE THIS: **Synthetic rubber is made by linking polymer molecules together. These are mainly polymers synthesized from petroleum by-products
1. A hydrocarbon mixture (from oil or coal) is created and refined.
2. Naphtha; a flammable liquid hydrocarbon mixture used to manufacture gasoline and plastics; is combined with natural gases. This reaction produces monomers, which bind molecules together to create polymers. Common monomers used to make synthetic rubbers include Styrene-Butadiene Rubber (SBR), Nitrile Rubber (NBR) and Butyl Rubber (IIR).
3. Chemical agents are used to turn the individual polymers into polymer chains. This forms a rubber substance.
4. In a process called vulcanisation, the rubber substance will be processed into a rubber product. Vulcanisation works by converting polymers into more durable material by adding accelerators such as sulphur.
5. The rubber is then moulded into the desired shape, before it undergoes quality assurance checks.
https://www.rugpadusa.com/articles/is-natural-rubber-better-than-synthetic-rubber-heres-what-we-know