How Rubber is Made

The Process of Making Rubber

Making rubber is a multi-step process that begins with a rubber tree or petrochemicals, and ends with a wide range of end products. Rubber stamps, shoes, rubber bands, wetsuits for surfers, hoses, and a plethora of industrial products are all made from rubber.

Rubber has been processed by human beings since as early as 1600 BC, when early indigenous Mesoamerican cultures produced stabilized rubber for containers, waterproofing, and recreational balls. 

The process of hardening rubber—vulcanization—was rediscovered by Charles Goodyear in 1839 when he accidentally dropped natural rubber on a hot stove, where it hardened and stabilized as it “cooked.”

Today, there is such a demand for rubber that much of it is synthetic, rather than the natural rubber that comes from rubber trees. The process for creating the two types is quite different, but both produce some of the essential objects for industry today.

Types of Rubber

The process of making rubber depends on the type of rubber you are talking about. The method for making natural rubber is completely different than the method for making synthetic rubber. Natural rubber begins with latex from a rubber tree, while synthetic rubber begins with a base of petrochemicals.

One species of rubber tree is mostly responsible for the majority of natural rubber that exists today, found natively in South America and common to Southeast Asian plantations. Different rubber trees produce different compositions of rubber.

How Natural Rubber is Made

When tappers peel back the bark of a rubber tree, they disrupt the plant ducts. This releases latex, a milky white substance. From there, the latex flows down the grooves and into large cups, where they are collected by rubber tappers and sent on their way to be processed into rubber as we know it. 

How is Latex Processed into Natural Rubber?

Rubber processing technically begins at the point of harvesting, when tappers take latex sap from rubber trees. 

Next, the latex is filtered and packaged into drums, then sent to be made into sheets. To achieve this, acid is added to the latex, causing the material to become clumpy. This clumpy fluid can be rolled into sheets in a mill, which removes water for drying and smoking.

Next comes prevulcanization, where the latex sheets are treated with chemicals and low, gentle heating. 

Once latex is ready to be made into smoked sheets of rubber, companies add acid to the latex. This causes the material to clump. The clumped fluid is then rolled into sheets in a mill. Doing so removes water, so the sheets can be dried and smoked.

Finally, latex is prevulcanized. Prevulcanization involves chemical treatments and gentle heating at low temperatures. With further heating, the material is turned into the hardened, black rubber with which we are all so familiar.

What is Synthetic Rubber?

Synthetic rubber production begins by using petrochemicals in chemical plants, including neoprene (polychloroprene) and emulsion styrene-butadiene rubber (E-SBR), the synthetic rubber that makes up most vehicle tires.

The production of synthetic rubber begins with oil, coal, or other hydrocarbons, which are refined to produce naphtha. Then, the naphtha is combined with natural gas to produce monomers, such as butadiene, styrene, isoprene, chloroprene, ethylene, or propylene. 

Then, the substance is polymerized using a catalyst and process steam. As a result, chains of polymers form to create rubber, which can be further vulcanized as needed. 

Natural Rubber versus Synthetic Rubber Properties 

Synthetic rubbers are available in many forms, thanks to the wide range of applications from the industrial market. A few examples include styrene-butadiene rubber, polybutadiene rubber, and polyisoprene rubber. 

Since synthetic rubber is used in vastly different ways, its properties vary from form to form. But in general, there are a few distinct differences between natural and synthetic rubber that are important to note.

Natural Rubber Properties

Natural rubber is resistant to wear from chipping and tearing thanks to its high tensile strength. Damages from heat, light, and ozone exposure, however, are more likely. Its tacky properties, especially toward steel cords, make it common in vehicle tires.

Synthetic Rubber

Synthetic rubber is more resistant to abrasion than natural rubber. Its grease and oil resistance also makes it a popular choice for corrosive environments.

Synthetic rubber also has a strong resistance to heat and time—many varieties of synthetic rubber are even flame-resistant. This makes it a common choice for electric insulation. Synthetic rubber is also flexible, even in relatively low temperatures. 

Synthetic rubber is more commonly used today because of its availability and ease of production, and in special circumstances that require its resistance to extreme temperatures and corrosion. 

To test the properties of your natural or synthetic rubber in a multitude of environments and situations, contact ACE Laboratories.

Uses of Synthetic Rubber 

Different types of synthetic rubber are used for different rubber products, depending on the variety’s unique properties. 

Polychloroprene (CR):

  • Laptop sleeves
  • Gaskets
  • Automobile fan belts
  • Hoses

Styrene-Butadiene (SBR):

  • Bus tires
  • Aircraft tires
  • Conveyor belts
  • Shoe soles

Ethylene Propylene Diene Monomer (EPDM):

  • Solar panel heat collectors
  • Mechanical vibrators
  • Electrical insulation
  • Radiators

Acrylonitrile Butadiene (NBR):

  • Lab gloves
  • Oil seals
  • Synthetic leather
  • V belts
  • O rings

Polysiloxane (SI):

  • Coatings
  • Sealants
  • Molds (in dentistry, etc.)

There are countless other applications for different synthetic rubbers, ranging from chewing gum to sporting goods to belts and moldings. 

Natural rubber is commonly used to produce high-performance vehicle tires that will need excellent tear strength, even at high temperatures caused by friction. Aircraft tires, heavy truck tires, and even sophisticated race car tires are often made from natural rubber.

What is Silicone Rubber?

Silicone rubber, like rubber, is an elastomer. To tell the two apart, it is necessary to look at the atomic structure of the two substances. Silicone’s backbone is made of silicon and oxygen, while most rubbers have backbones made of carbon-carbon bonds. 

Silicone is typically non-reactive, stable, and extreme-environment resistant. Compared to rubber, silicone is more heat-, chemical-, and ozone-resistant. 

Silicone Rubber Uses

Silicone and cured silicone rubber’s desirable properties make it common in a wide range of products. 

Silicone rubber can be found in insulators, automobiles, cooking, baking, and food storage products, apparel—especially sportswear—and footwear. Silicone rubber is also commonly found in electronics, medical devices, and in silicone sealants for home repair. 

Rubber Testing Services from ACE Laboratories

Ready to test the limits of your natural or synthetic rubber material? ACE’s state-of-the-art ISO/IEC 17025 accredited laboratory and rubber testing experts are here to help. 

Tell us about your challenges and goals today—we’re ready to get to work!

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