Define Isoprene

Isoprene is a volatile and colourless liquid hydrocarbon. The compound is formed as a by-product of processing coal tar or petroleum. The compound is commonly used as a chemical raw material. Its molecular formula is C5H8.

Isoprenes are known as building blocks. They are responsible for the biosynthesis of the common terpenes. The primary role of isoprene is as a plant metabolite. It is usually termed as an alkadiene, hemiterpene, and volatile organic compound. The IUPAC name is 2-methyl-1,3-butadiene.

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Introduction to Polyisoprene

Polyisoprene is a polymer of isoprene. It is a primary chemical constituent of natural rubber. Polyisoprene is a natural compound that also occurs in resins, balata and gutta-percha, and synthetic equivalents of the three materials. 

Based on the compound's molecular structure, polyisoprene can be an elastic or a resilient polymer. For instance, natural rubber is a milky liquid, while isoprene rubber is a tough, leathery resin in natural and synthetic balata or gutta-percha.

Polyisoprene is built up from the linking of multiple isoprene molecules leading to four isomers, out of which the most important are the cis and trans isoprene.

What is Cis-Isoprene?

Natural rubber comprises exclusively of cis-1,4 polymer, produced in the milky latex of certain plants. The uniqueness of the natural rubber lies in its physical property of toughness and extensibility. 

In the absence of tensile stress, the polymer chains of the cis-1,4 polymer assume a disordered or amorphous arrangement. 

Natural rubber is said to be self-reinforcing. However, it gets greatly affected by temperature resulting in a sticky and inelastic substance. 

The polymerization of synthetic isoprene manufactures isoprene rubber. The rubber is acquired from the thermal cracking of the naphtha fraction of petroleum. The polymerization is conducted in solutions making use of the Ziegler-Natta and anionic catalysts.

The polymerization leads to cis-1,4 polyisoprene with irregular structure, which does not crystallize readily, and which is not tacky or firm as the raw material.

Isoprene rubber is a complete substitute for natural rubber, and its principal usage is in tires, rubber springs, and mountings. Footwear is an essential application of isoprene rubber.

What is Trans-Isoprene?

Trans-1,4 polyisoprene is the dominant isomer in the two materials that imitate natural rubber- balata and gutta-percha. These materials are derived from the milky exudate of certain plants or trees. 

Unlike the cis-1,4 polymer, the trans-1,4 polymer is highly crystalline. This property leads to the formation of tough, complex, and leathery materials. Their stealth properties, balata, and gutta-percha were commonly used in the 19th century as sheathings for underwater cables and golf balls. 

Ziegler-Natta catalysts can also be synthesized to obtain trans-1, 4 polymers, yielding a synthetic balata of similar properties employed in golf-ball covers and orthopedic devices braces and splints.

Introduction to Isoprene Terpene

Isoprene terpenes are the single largest class of compounds found in essential oils known as isoprenoids made up of isoprene molecules. Each isoprene molecule comprises five C atoms with double bonds. 

The simplest forms of terpenes are monoterpenes that consist of two isoprene molecules. Sesquiterpenes consist of three isoprene molecules, and diterpenes consist of four isoprene molecules. 

Terpenes are - cyclic and acyclic groups, which indicate their structure. Cyclic terpenes usually form a ring, while Acyclic terpenes include linear. A few terpenes occur as essential oils like the monocyclic, bicyclic, and tricyclic monoterpenes.

Terpene hydrocarbons are thermally labile and can be easily oxidized, and hold excellent anti-inflammatory, antiseptic, antiviral, analgesic properties, and antibacterial properties.

What is Isoprene Uses and Isoprene Price?

Due to the outstanding mechanical properties and low cost, isoprene rubber is the most preferred material for several engineering applications. The typical isoprene uses include tires, adhesives, anti-vibration mounts, springs, drive couplings, and bearings. The most significant portion of the produced NR and IR is used for tires as it is a usual blend with SBR and PBD rubber to achieve superior performance.

Polyisoprenoids are used for numerous rubber applications, including medical equipment, shoe soles, baby bottle nipples, elastic films, toys, and threads for golf balls or textiles. Other uses of isoprene include paints, adhesives, and coatings. Styrene-isoprene rubber is a copolymer whose primary use is in pressure-sensitive bonds.

Crude isoprene is used in electrical insulating tapes, cement, and cable wrapping.

The industrial uses of isoprene include processing aids- specific to petroleum, feedstock, processing aids, and intermediates. 

The standard and the latest isoprene price is ₹ 155 per  Kilogram. However, the other derivatives of isoprene vary based on the constituents and the method of production. 

FAQs (Frequently Asked Questions)

1. What are the Properties of Isoprene Rubber?

Ans: Polyisoprene is an inexpensive and widely-used commercial rubber, while natural rubber is the only non-synthetic rubber. Natural and synthetic rubber differ in the microstructure, while the natural rubber consists of cis-1,4 polymer, the synthetic isoprene is a blend of both 3,4 vinyl polymer and cis-1,4, and trans-1,4 polymers. 

The amount of cis-1,4 in natural rubber ranges from 90 to 98 percent. An increase in cis-1,4 shows properties such as lowering the glass transition temperature, improving mechanical strength, and increasing crystallinity. Thus, synthetic polyisoprene's tear resistance and tensile strength are generally lower than those of natural rubber.

Both natural and vulcanized rubber hold resistance and are the most preferred choice for dynamic applications at ambient and low temperatures. 

2. What is Cis-Trans Isomerization in Natural Polyisoprenes?

Ans: Isoprene cis trans isomers are of several conjugated polyolefins and simple olefins. The action of light, heat can interconvert, or various other catalysts that change geometric configuration that can be readily followed, and the isomers can be separated and identified. 

The isomerization in natural polyisoprene for isoprene cis-trans rubber is done by converting by the reaction with a small amount of a thiol acid. This isomerization process converts into a modified rubber which crystallizes at low temperatures much more slowly than the natural or original rubber. This change in crystallization rate is probably due to converting some of the cis double bonds into the trans configuration in natural rubber.