Synthetic polyisoprene rubbers creep

A true synthetic natural rubber was introduced in the mid-1960s with the exact same chemical structure as latex tapped from a tree. The difference is that natural rubber comes with a variety of other ingredients in the latex that can both add and detract from performance, while polyisoprene is considered relatively pure. In addition, there are some differences in molecular weight distribution that impact performance. Available in both latex and solid forms, this elastomer can be directly substituted for natural rubber in many applications. Adhesives which are not cured tend to have higher creep values than natural rubber, but also exhibit lower tack and green strength properties. Vulcanized adhesive products perform equal to cured natural rubber adhesive products. 

CREEP CHARACTERISTICS OF NATURAL RUBBER AND SYNTHETIC POLYISOPRENES (CREEP RATES IN PERCENTAGE PER DECADE UNDER A 4 1 SHEAR TO COMPRESSION RATIO AT 23 °C)... 

Vulcanization converts the material from a high viscosity liquid to an amorphous solid, suppressing creep and flow, and enhancing long-range rubber elasticity. Because cis-polyisoprenes crystallize on extension, they form extremely tough, self-reinforcing materials. Before the advent of synthetic rubber such as SBR, natural rubber was the only material for automobile tires. Nowadays, it remains the material of preference for heavy-duty tires such as are used by airplanes and trucks. 

Synthetic high c/ y-polyisoprenes exhibit even better low creep properties than natural rubber in identical formulations and for this reason the synthetic polymers are finding increasing usage in high quality engineering applications. 

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