Guides
If you’re looking to learn more about natural rubber, whether for sourcing or simply to educate yourself, this article is for you. We’ve prepared this short guide on the basics of this material, including its definition, properties, method of manufacture, and applications.
Natural rubber is made up of long isoprene polymer chains, loosely connected. The chains reattach themselves when pulled apart; this gives rubber its elasticity. As opposed to synthetic rubbers, which are made from petrochemicals, natural rubber is made from the latex sap of rubber trees (although other plants also produce latex, rubber trees are the most efficient at producing rubber, making them the suppliers of latex for 99% of natural rubber).
Natural rubber has flexibility and strength, as well as impurities and vulnerability to environmental conditions and hydrocarbons. Compared to other rubbers, natural rubber is one of the most flexible types, and it’s resistant to water and certain chemicals. It’s also resistant to cutting, tearing, wear, fatigue, and abrasion, with a working range between -58 to 212 degrees F. Additionally, it has a lot of tensile strength and adheres easily to other materials.
However, natural rubber isn’t as effective at resisting heat, light and ozone as other rubbers like neoprene. The material also varies with the tree it’s produced from, as well as containing natural impurities. While natural rubber is resistant to water and some chemicals, it’s still vulnerable to fuel, oil, and non-polar solvents.
Natural rubber must first be tapped from a rubber tree, then processed with chemicals and heat to be used in manufacturing. The tree is cut and the sap drips into a cup. A third of the latex is rubber at this point, held in a colloidal suspension, and another third is water. To refine the latex into rubber, latex is mixed with formic acid to make it the rubber coagulate into curds, which are then washed and pressed into blocks or pressed into sheets that are then smoked.
Next the rubber is put through masticating machinery to make it more workable, then mixed with chemicals to improve its properties. Finally it’s made into a form, either by calendaring or extrusion, then vulcanized, which makes it more durable, elastic, and resilient. Vulcanization involves heating the rubber with some sulfur in a pressure cooker at around 320 degrees F, although it can also be steam cured, microwaved, or sent through a fluidized bed or molten metal salts to be vulcanized. The vulcanization cross-links molecular chains of polyisoprene to add strength and chemical resistance, and remove the stickiness of raw rubber. Even though artificial rubber was invented in the 1930s, natural rubber is still widely used today, making up a little under half the market.
Natural rubber is used in applications requiring a high level of wear and heat resistance. Thanks to its strength and compressibility, natural rubber is used in engineering applications, like anti-vibration mounts, drive couplings, springs, bearings, rubber bands, and adhesives. But the majority- 50% of natural rubber- is used in high-performance tires for race cars, buses, and aircraft thanks to its strength and heat resistance. It’s also used in hoses, automotive parts, foam mattresses, and battery boxes.
However, thanks to its adhesive properties, natural rubber is also found in rubber cement and the soil stabilization materials used around new roads. Even raw rubber is sometimes used for adhesives and as part of shoe soles. Additionally, about 10% of latex harvested from trees is simply reduced down to 60% rubber solution to make products like latex gloves or to use as a coating.
This guide has summarized the definition, properties, manufacturing process, and applications of natural rubber. We hope this information helps you with your supplier search. For more information on the various types of rubber, you can read through our rubber guide. If you’re more interested in finding suppliers, we invite you to check out Thomasnet, where we have profiles on more than 70 natural rubber suppliers.
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