Rubbers (polyisoprene and polybutadiene)

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Rubbers

There are many different kinds of rubber, but they all fall into two broad types: natural rubber (latex—grown from Plants) and synthetic rubber (made artificially in a chemical plant or laboratory). Commercially, the most important synthetic rubbers are styrene butadiene (SBR), polyacrylics, and polyvinyl acetate (PVA); other kinds include Polyvinyl chloride (PVC), polychloroprene (better known as neoprene), and various types of polyurethane. Although natural rubber and synthetic rubbers are similar in some ways, they’re made by entirely different processes and chemically quite different.

Polyisoprene

Polyisoprene, polymer of isoprene (C5H8) that is the primary chemical constituent of natural rubber, of the naturally occurring resins balata and gutta-percha, and of the synthetic equivalents of these materials. Depending on its molecular structure, polyisoprene can be a resilient, elastic polymer (elastomer), as in the case of natural rubber and isoprene rubber, or a tough, leathery resin, as in the case of natural and synthetic balata or gutta-percha.

The chemical structure of isoprene can be represented as CH2=C(CH3)—CH=CH2. Polyisoprene—built up from the linking of multiple isoprene Molecules—can assume any one of four spatial configurations, or isomers, each of which imparts a unique set of properties to the polymers. As the repeating units of polyisoprene, the four isomers have the following structures:

Of these four isomers, the most important are the cis-1,4 polymer and the trans-1,4 polymer.

Cis-1,4 Polyisoprene

Natural rubber consists almost exclusively of the cis-1,4 polymer, which is produced in the milky latex of certain plants—most notably the rubber tree (Hevea brasiliensis). The uniqueness of natural rubber lies in its physical properties of extensibility and toughness, summarized by its ability to be stretched repeatedly to seven or eight times its original length. In the absence of tensile (stretching) Stress, the polymer chains assume an amorphous, or disordered, arrangement. On being stretched, however, the molecules readily align into an ordered crystalline arrangement. Crystallinity lends greater strength to the material, so natural rubber is considered to be “self-reinforcing.” In its natural state, however, natural rubber is greatly affected by temperature: it crystallizes on cooling, taking only several hours to do so at −25 °C (−13 °F), and it becomes tacky and inelastic above 50 °C (120 °F). In addition, it is swollen and weakened by hydrocarbon oils, and it reacts with Oxygen and ozone in the Atmosphere, leading to rupture of the polymer molecules at the carbon-carbon double Bonds and softening and cracking of the material over time. These disadvantages are overcome to a great extent by cross-linking the polymer chains through the process known as vulcanization.

Isoprene rubber (IR) is manufactured by the polymerization of synthetic isoprene, which is obtained from the thermal cracking of the naphtha fraction of petroleum. Polymerization is conducted in solution, using both anionic and Ziegler-Natta catalysts. The product is at most 98 percent cis-1,4 polyisoprene, and its structure is not as regular as natural rubber in other respects. As a result, it does not crystallize as readily as the natural material, and it is not as strong or as tacky in the raw (unvulcanized) state. In all other respects, though, isoprene rubber is a complete substitute for natural rubber. For both materials, the principal usage is in tires, although these elastomers are also preferred for rubber springs and mountings, owing to their good fatigue resistance and high resilience. Footwear is an important application, and natural rubber is still used in adhesives (such as rubber cement).

Trans-1,4 Polyisoprene

Trans-1,4 polyisoprene is the dominant isomer in gutta-percha and balata, two materials that, like natural rubber, are derived from the milky exudate of certain trees. Unlike the cis-1,4 polymer, however, the trans-1,4 polymer is highly crystalline, so balata and gutta-percha are tough, hard, and leathery materials—properties that led in the 19th century to their use as sheathings for underwater cables and golf balls. The trans-1,4 polymer can also be synthesized with Ziegler-Natta catalysts, yielding a synthetic balata of similar properties that also is employed in golf-ball covers as well as in orthopedic devices such as splints and braces.

Polybutadiene (Butadiene rubber)

Butadiene rubber, synthetic rubber widely employed in tire treads for trucks and automobiles. It consists of polybutadiene, an elastomer (elastic polymer) built up by chemically linking multiple molecules of butadiene to form giant molecules, or polymers. The polymer is noted for its high resistance to abrasion, low heat buildup, and resistance to cracking.

Much of the butadiene rubber produced is blended with natural rubber (polyisoprene) or with styrene-butadiene rubber to give it improved resilience and lower rolling resistance. More than half of all usage is in tires; other applications are footwear, wire and cable insulation, and conveyor belts. Polybutadiene is also processed with styrene monomer in order to produce a high-impact polystyrene and with styrene and acrylonitrile monomer in order to produce a high-performance plastic known as acrylonitrile-butadiene-styrene copolymer.

Applications of Polybutadiene

Polybutadiene is the second largest volume synthetic rubber produced, next to styrene-butadiene rubber (SBR). Consumption was about 1,953,000 metric tons worldwide in 1999.

 

Polybutadiene in Tyres

The major use of polybutadiene is in tyres with over 70% of the polymer produced going into treads and sidewalls. Cured BR imparts excellent abrasion resistance (good tread wear), and low rolling resistance (good fuel economy) due to its low glass transition temperature (Tg). The low Tg, typically <–90C, is a result of the low “vinyl” content of polybutadiene, which will be discussed below. However, low Tg also leads to poor wet traction properties, so polybutadiene is usually blended with other elastomers like natural rubber or styrene-butadiene rubber for tread compounds.

Polybutadiene as an Impact Modifier in Other Polymers

Polybutadiene also has a major application as an impact modifier for polystyrene and acrylonitrile-butadiene-styrene resin (ABS) with about 25% of the total volume going into these applications. Typically about 7% polybutadiene is added to the polymerisation process to make these rubber-toughened resins.

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Introduction to Rubbers

Rubber is an elastomer, a material that can be stretched and deformed under stress and then return to its original shape. Rubber is made from the sap of certain trees, such as the rubber tree (Hevea brasiliensis). The sap is a milky white liquid called latex. Latex is a suspension of tiny rubber particles in water. The rubber particles are made up of long chains of molecules called polymers.

Natural Rubber

Natural rubber is the most common type of rubber. It is made from the sap of the rubber tree. The sap is collected and then processed to remove the water. The remaining rubber is then dried and rolled into sheets. Natural rubber is a soft, elastic material that is used in a variety of products, including tires, shoes, and gloves.

Synthetic Rubber

Synthetic rubber is made from petroleum products. It is a more durable and versatile material than natural rubber. Synthetic rubber is used in a variety of products, including tires, hoses, and gaskets.

Polyisoprene Rubber

Polyisoprene rubber is a type of synthetic rubber that is made from the monomer isoprene. It is a very similar material to natural rubber, but it is more resistant to wear and tear. Polyisoprene rubber is used in a variety of products, including tires, shoes, and gloves.

Polybutadiene Rubber

Polybutadiene rubber is a type of synthetic rubber that is made from the monomer butadiene. It is a very strong and elastic material. Polybutadiene rubber is used in a variety of products, including tires, hoses, and gaskets.

Properties of Rubbers

Rubbers are characterized by their elasticity, which is their ability to return to their original shape after being stretched or deformed. Rubbers are also characterized by their resilience, which is their ability to absorb energy when they are deformed.

Applications of Rubbers

Rubbers are used in a wide variety of applications, including:

  • Tires
  • Shoes
  • Gloves
  • Hoses
  • Gaskets
  • Belts
  • Seals
  • O-rings
  • Vibration dampers
  • Shock absorbers
  • Adhesives
  • Sealants
  • Coatings

Manufacturing of Rubbers

Rubbers are manufactured by a process called polymerization. Polymerization is a Chemical Reaction in which small molecules called monomers are joined together to form large molecules called polymers. The type of rubber that is produced depends on the type of monomer that is used.

Recycling of Rubbers

Rubbers can be recycled in a number of ways. One way is to grind them up and use them as a filler in other products. Another way is to melt them down and remold them into new products. Rubbers can also be recycled into fuel.

Future of Rubbers

The future of rubbers looks bright. Rubber is a versatile material that is used in a wide variety of applications. As the world’s Population continues to grow, the demand for rubber is expected to increase. Rubber manufacturers are working to develop new and innovative ways to produce rubber that is more sustainable and environmentally friendly.

What is rubber?

Rubber is an elastomer, a material that can stretch and return to its original shape. It is made from the sap of rubber trees, which is a milky fluid called latex.

What are the different types of rubber?

There are many different types of rubber, but the most common are natural rubber, synthetic rubber, and vulcanized rubber. Natural rubber is made from the sap of rubber trees, while synthetic rubber is made from petroleum products. Vulcanized rubber is a type of rubber that has been treated with sulfur to make it more durable.

What are the properties of rubber?

Rubber is a versatile material with many properties that make it useful in a variety of applications. It is elastic, meaning that it can stretch and return to its original shape. It is also waterproof, making it ideal for use in products that need to be protected from water. Rubber is also resistant to abrasion, making it a good choice for products that need to withstand wear and tear.

What are the uses of rubber?

Rubber is used in a wide variety of products, including tires, shoes, gloves, and gaskets. It is also used in construction, automotive, and industrial applications.

How is rubber made?

Rubber is made from the sap of rubber trees. The sap is collected and then processed to remove impurities. It is then mixed with other ingredients, such as sulfur, and heated to form a liquid. The liquid is then poured into molds and allowed to cool and harden.

What are the advantages of rubber?

Rubber is a versatile material with many advantages. It is elastic, waterproof, and resistant to abrasion. It is also relatively inexpensive and easy to work with.

What are the disadvantages of rubber?

Rubber is not as strong as some other materials, such as Metal. It is also susceptible to damage from heat and sunlight.

How is rubber recycled?

Rubber can be recycled in a number of ways. It can be shredded and used to make new products, such as playground equipment and flooring. It can also be used to make fuel or other chemicals.

What is the future of rubber?

The future of rubber is bright. The demand for rubber is expected to grow in the coming years, driven by the Growth of the automotive and construction industries. New technologies are also being developed to make rubber more sustainable and environmentally friendly.

Sure, here are some MCQs without mentioning the topic Rubbers (polyisoprene and polybutadiene):

  1. Which of the following is a type of elastomer?
    (A) Natural rubber
    (B) Synthetic rubber
    (C) Both natural and synthetic rubber

  2. What is the main difference between natural rubber and synthetic rubber?
    (A) Natural rubber is made from plants, while synthetic rubber is made from petroleum.
    (B) Natural rubber is more elastic than synthetic rubber.
    (C) Natural rubber is more durable than synthetic rubber.

  3. What are some of the properties of rubber?
    (A) Elasticity
    (B) Durability
    (C) Resistance to wear and tear
    (D) All of the above

  4. What are some of the uses of rubber?
    (A) Tires
    (B) Shoes
    (C) Belts
    (D) All of the above

  5. What is the future of rubber?
    (A) Rubber is a declining Industry.
    (B) Rubber is a growing industry.
    (C) Rubber is a stable industry.

  6. What are some of the challenges facing the rubber industry?
    (A) Competition from other materials
    (B) Environmental concerns
    (C) Rising costs of raw materials
    (D) All of the above

  7. What are some of the opportunities facing the rubber industry?
    (A) New applications for rubber
    (B) Development of new rubber products
    (C) Growth in emerging markets
    (D) All of the above

  8. What are some of the key players in the rubber industry?
    (A) Bridgestone
    (B) Michelin
    (C) Goodyear
    (D) All of the above

  9. What are some of the trade associations representing the rubber industry?
    (A) Rubber Manufacturers Association
    (B) International Rubber Association
    (C) European Tyre and Rubber Manufacturers Association
    (D) All of the above

  10. What are some of the research organizations working on rubber technology?
    (A) Malaysian Rubber Board
    (B) Indian Rubber Manufacturers Association
    (C) Chinese Rubber Industry Association
    (D) All of the above