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  • Common name:
    NR or Natural Rubber
  • Common chemical composition:

Natural rubber has various fundamental properties

  • Excellent adhesion properties in the raw form that cannot be surpassed by any elastomer;
  • High tensile strength, surpassed only by urethane elastomers;
  • Low hysteresis heating;
  • High gas permeability;
  • High electrical resistance;
  • Very low weather resistance;
  • Good abrasion and tear resistance;
  • Almost no resistance to oils and hydrocarbons;
  • Over-vulcanization with 30% sulphur produces Ebonite, a rigid and fragile substance that is highly resistant to chemicals.

General properties

Natural rubber is a macromolecular substance composed of just carbon and hydrogen atoms. Its molecular formula is (C5H8)n,with one double bond for every 5 carbon atoms (with the CIS configuration). It has the cis-1,4-polyisoprene structure, with a repetitive monomer unit. Natural rubber, while possessing many useful properties, also has certain negative characteristics.
At one time, rubber products were sticky and smelly, deforming when warm and becoming brittle when cold. Thus, mechanical treatments and compounds of suitable additives were tried to stabilize the properties of rubber. Success was initially achieved using the masticator with concentric cylinders devised by T. Hancock, which weakened the material and made it more flexible and suitable for absorbing additives (1820). Then, chemical and physical processing methods for the compounds were researched and, using suitable solvents (ether, turpentine, oil), relatively stable rubber solutions were obtained, suitable for waterproofing fabrics (C. MacIntosh, 1823) and producing flexible threads (T. Hancock, 1837).

Complete stability of the properties of rubber was achieved in 1839 by Charles Goodyear who invented vulcanization, a process which creates cross-links between the polymer chains by heating rubber in the presence of sulfur. Cross-linking increases the strength of rubber and serves as “memory” in a certain sense, helping the polymer revert to its original shape after being stressed.

Fields of application

Natural rubber has various fields of application. It is used in the automotive industry.
Natural rubber is also excellent for finished parts that come into contact with salt water such as subsea pipe gaskets. Another important use of this rubber type is in the naval sector where it is used in engine mounts, flexible joints and applications featuring contact with sea water.

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