Welcome back to The Mechanical post ! Today let's see what is rubber in detail.

Rubber is one of the most widely used material and is present everywhere be it in your office in the form of rubber band or the swimming goggles. Originally, rubber comes from natural sources in the form of latex—grown from plants. However now-a-days synthetic rubbers have replaced the traditional ones. Now let's see what is rubber made of :



Some people get confused between rubber and plastic, so to clear your doubts we have written a short and detailed post on Plastics. Coming back to the topic, Rubbers are highly elastic and resilient polymeric materials, which have numerous applications in various fields. Natural and synthetic rubbers are also known as elastomers.They are organic polymers which are have the capability of being subjected to huge amount of elastic strain without plastic yielding. They can be stretched upto 1000% of their original size.

Natural rubber is a vegetable product which is obtained from a variety of plants like Amazonian rubber tree (Hevea brasiliensis), Dandelion etc. It has excellent flexure characteristics. It is used in automobile tubes and tyres, raincoat, floor mats, erasers etc.

Foam rubber is a type of rubber made by incorporating gas into latex and after that a process of vulcanisation. Sponge rubber is produced from dry natural or synthetic rubber into which a blowing agent such as sodium bicarbonate and fatty acid injected.

A synthetic rubber is an artificial elastomer. These are polymers synthesized from petroleum byproducts. Synthetic rubber offer a unique range of physical and chemical properties, which makes it more suitable for specific applications. Synthetic rubbers are materials with rubber like qualities, but they are not elastic as rubber. There are many types of synthetic rubbers viz, methyl rubber, neoprene, buna rubber etc.

Chloroprene ( Neoprene ) Rubber (CR).

Neoprene is a type of synthetic rubber formed by the free - radical polymerization of choloroprene. Neoprene was invented by DuPont scientist on April 17, 1930. Laptop sleeves are a good example of its application.

Properties of Chloroprene ( Neoprene ) Rubber:

  1. Neoprene is resistant to oils, chemical, sunlight, weathering, aging and ozone is outstanding.
  2. It maintains its properties without any changes at temperature upto 120 degree celcius.
  3. Neoprene is a type of elastomer which does not support combustion, but it does get consumed by fire.
  4. Neoprene is chemically and structurally similar to natural rubber and its mechanical properties are also similar.
  5. It has excellent resistant to permeability by gases.
  6. It can be used for low voltage insulation, but is relatively low in dielectric strength.

Applications of  Chloroprene ( Neoprene ) Rubber :

  1. They are used for heavy duty conveyor belts
  2.  V-belts
  3.  hose covers
  4. footware
  5.  brake diaphragams
  6.  motor mounts
  7.  rolls and gaskets.

Styrene Butadiene Rubber (SBR) or Buna "S" or GR-S.

SBR is synthesized from two monomers, styrene and butadiene. It is an industrial material which locks horn with natural rubber. The elastomer is used widely in pneumatic tires.

Properties of styrene butadine rubber :

  1. These are a type of elastomers.
  2. These are copolymers of butadiene and styrene.
  3. They are similar in many ways to the natural rubbers.
  4. They are widely used because of their low cost.
  5. They are non-oil resistant and are generally poor in chemical resistant.
  6. They have excellent impact and abrasion resistance.
  7. They are low in tensile strength , resilience, hytersis than natural rubber.

Applications:

  • They are used to manufacture auto and airplane tyres
  • belting
  • flooring
  • wire and cable insulation
  • footwear.                                                                                                                       

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Nitrile Butadiene Rubber (NBR).

Nitrile Rubber, or “Nitrile butadiene rubber (NBR)” is a type of synthetic rubber that is often used where resistance to fuel, oils and chemicals is required. NBR is also used as a billet in extrusion of various products. Other common names of NBR innclude Perbunan, Nipol, Krynac and Europrene.

Properties Nitrile Butadiene Rubber (NBR) :

  1. Nitrile elastomers are originally known as Buna "N".
  2. These are the copolymers of acrylonitrile and butadiene.
  3. They are principally know for their outstanding resistance to oil and fuels at both normal and elevated temperatures.
  4. Their properties can be changed by varying the ratio of acrylonitrile and butadiene.
  5. Nitrile groups are low in most mechanical properties.
  6. Their tensile strength is low because they do not crystallize appreciably when stretched.
  7. Resilience of this material is roughly one third to one-half of natural rubber.
  8. Their electrical insulation quality varies from fair to poor.

Applications Nitrile Butadiene Rubber (NBR) :

  1. Low-acrylonitrile grades are used where good flexibility at low temperature is of primary importance.
  2. Medium range types which are the most widely used, find applications between these extremes.
  3. They are used for flexible couplings, printing blankets, rubber rollers and washing machine parts.

Silicones.

They belong to the unique class of polymers which are not based on carbon element, but on silicon. They have -Si-O-Si backbone and are widely used inorganic polymer. A variety of silicon polymers can be produced ranging from low viscous fluids of linear chain to rigid cross-linked chain.
Silicons, also known as polysiloxanes, are polymers that include any inert, synthetic compound made up of repeating units of siloxane, which is a chain of alternating silicon atoms and oxygen atoms, combined with carbon, hydrogen and sometimes other elements. Thy are typically heat-resistant and either liquid or rubber-like.
Most common are materials based on polydimethylsiloxanepolydimethylsiloxane, which is derived by hydrolysis of dimethyldichlorosilane. This dichloride reacts with water.

Properties of silicone :

  1. Low thermal conductivity.
  2. Low chemical reactivity ( chemical inert ).
  3. Low toxicity.
  4. Thermal stability ( constancy of properties over a wide temperature range of  -100 to 250*C).
  5. The ability to repel water and form watertight seal.
  6. Does not stick to many substrates, but adheres very well to other, e.g. glass.
  7. Good electrical properties.
  8. Does not support microbiological growth.

Applications of silicone :

  • Silicon are used in sealants
  • adhesives
  •  lubricants
  •  medicine
  • cooking utensils and thermal and electrical insulation

Some common forms include silicone oil, silicone grease, silicone rubber, silicone resin, and siliconecaulk.

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