Key Difference – Natural vs Synthetic Rubber
Rubber can be produced in two ways; either naturally or artificially. Both natural and synthetic rubber can be vulcanized, mostly with sulfur; but on some special occasions, other agents are also used depending on the required properties. The key difference between natural rubber and synthetic rubber is their origin. Both are polymers, but natural rubber is produced from the latex obtained from a tree, whereas synthetic rubber is an artificial polymer produced by using petroleum byproducts. They have different physical and chemical properties and their industrial applications vary depending on those properties. A large quantity of rubber is used to manufacture automobile tires.
What is Natural Rubber?
Natural rubber tree, Hevea brasilensis is a native tree to Brazil; it also grows in South East Asia, Africa, and South America. Natural rubber is a polymer which is made from the sap collected from this rubber tree. After collecting the sap, it is exposed to air under the mild heat.
The monomer of natural rubber is 2-methyl-1,3-butadiene (isoprene), CH2=C(CH3)-CH=CH2. The polymerization reaction is:
nCH2=C(CH3)-CH=CH2 -[CH2-C(CH3)=CH-CH2]n–
Natural rubber became economically valuable after the development of vulcanized rubber (heating in the presence of sulfur) by Charles Goodyear. It gives a very good rubbery, durable and coherent texture.
What is Synthetic Rubber?
Synthetic rubber is an artificially produced polymer which is synthesized from petroleum byproducts. Synthetic rubber also has many industrial applications similar to natural rubber; in the field of the automotive industry for tires, hoses, belts, flooring, doors, and windows.
Compared to natural rubber, the notable benefit of synthetic rubber includes good oil and temperature resistance and the ability to produce a product with an extremely constant quality. The synthetic polymer produced from butadiene is considered as the most important synthetic rubber polymer.
What is the difference between Natural and Synthetic Rubber?
Composition & Production:
Natural Rubber: Natural rubber is a natural polymeric compound produced from the latex of Hevea brasiliensis. It mainly contains poly-cis-isoprene and some trace impurities such as proteins and dirt.
Synthetic Rubber: Synthetic rubber is a man-made polymeric material which is produced by the polymerization of various petroleum-based precursors which are known as monomers. The most commonly available synthetic rubber material is styrene-butadiene, synthesized from the copolymerization of styrene and 1,3-butadiene. Some of the other synthetic rubber polymers are produced by polymerization of monomers such as isoprene (2-methyl-1,3-butadiene), chloroprene (2-chloro-1,3-butadiene), and isobutylene (methylpropene) by adding a small quantity of isoprene for cross-linking. These polymers are mixed with some other monomers in different proportions to change their physical, chemical and mechanical properties.
Properties:
Natural Rubber: Natural rubber is a high molecular weight polymeric material and an elastomer with viscoelastic properties. It is insoluble in many solvents such as water, alcohol, acetone, dilute acids and alkalis. But, it is soluble in ether, carbon disulfide, carbon tetrachloride, petrol, and turpentine. Raw natural rubber possesses low tensile strength and abrasion resistant.
Synthetic Rubber: There is a huge range of synthetic rubber varieties, and their properties vary from one type to another. Some of the most important synthetic rubbers along with their properties are listed below.
| Category | Properties |
| Styrene butadiene rubber (SBR) | abrasion resistance, lower elasticity, better heat and aging resistance, excellent electrical insulation properties |
| Polybutadiene rubber (BR) | blended with SBR or NRabrasion-resistant, good elasticity, flexible at low temperatures |
| Isoprene rubber (IR) | more uniform cleaner, transparent |
| Acrylonitrile butadiene rubber (NBR) | Oil and fuel resistant, good heat distortion temperature properties, abrasion resistant |
| Chloroprene rubber (CR) | Flame retardant, resistant to grease, oil, weathering and aging, abrasion resistant |
| Butyl rubber (IIR) | Low permeability to gases, resistant to aging, ozone and chemicals, good mechanical properties, abrasion resistant, good electrical insulation properties |
Image Courtesy:
1. Latex being collected from a tapped rubber tree By Mohd Hafiz Noor Shams – Transferred from ml.wikipedia to Commons by Sreejithk2000 using CommonsHelper., [CC BY 2.5], via Wikimedia Commons
2. NBR balles By Cjp24 – Own work, [CC BY-SA 3.0], via Wikimedia Commons