Latex is the polymer cis-1,4-polyisoprene) – with a molecular weight of 100,000 to 1,000,000. Typically, a small percentage (up to 5% of dry mass) of other materials, such as proteins, fatty acids, resins and inorganic materials (salts) are found in natural rubber. Polyisoprene can also be created synthetically, producing what is sometimes referred to as "synthetic natural rubber", but the synthetic and natural routes are completely different
Some natural rubber sources called gutta-percha are composed of trans-1,4-polyisoprene, a structural isomer that has similar, but not identical, properties.
Natural rubber is an elastomer and a thermoplastic. Once the rubber is vulcanized, it will turn into a thermoset. Most rubber in everyday use is vulcanized to a point where it shares properties of both; i.e., if it is heated and cooled, it is degraded but not destroyed.
The final properties of a rubber item depend not just on the polymer, but also on modifiers and fillers like carbon black, factice, whiting, and a host of others.
Read more about this topic: Rubber
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