LYCOS RETRIEVER 
Rubber: United States
built 281 days ago
Natural rubber is obtained from the milky secretion (latex) of various plants, but the only important commercial source of natural rubber (sometimes called Pará rubber) is the tree Hevea brasiliensis. The only other plant under cultivation as a commercial rubber source is guayule (Parthenium argentatum), a shrub native to the arid regions of Mexico and the SW United States. To soften the rubber so that compounding ingredients can be added, the long polymer chains must be partially broken by mastication, mechanical shearing forces applied by passing the rubber between rollers or rotating blades. Thus, for most purposes, the rubber is ground, dissolved in a suitable solvent, and compounded with other ingredients, e.g., fillers and pigments such as carbon black for strength and whiting for stiffening; antioxidants; plasticizers, usually in the form of oils, waxes, or tars; accelerators; and vulcanizing agents. The compounded rubber is sheeted, extruded in special shapes, applied as coating or molded, then vulcanized. Most Pará rubber is exported as crude rubber and prepared for market by rolling slabs of latex coagulated with acid into thin sheets of crepe rubber or into heavier, firmly pressed sheets that are usually ribbed and smoked.
Source:
When rubber is stretched the "loose pieces of rope" are taut and ... no longer able to oscillate. Their kinetic energy is given off as excess heat. Therefore, the entropy decreases when going from the relaxed to the stretched state, and it increases during relaxation. This change in entropy can also be explained by the fact that a tight section of chain can fold in fewer ways (W) than a loose section of chain, at a given temperature (nb. entropy is defined as S=k*ln(W)). Relaxation of a stretched rubber band is thus driven by an increase in entropy, and the force experienced is not electrostatic, rather it is a result of the thermal energy of the material being converted to kinetic energy.
Source:
The polymer rubber chains exist in random loose clumps in the unstretched state. At the nipple end of the balloon, there is lots of rubber and therefore many, many polymer chains - still loosely coiled. These chains can be pierced without popping the balloon because the the chains can still be stretched. This is because they allow the skewer in between the chains without breaking the chains or the bonds that connect them. But on the sides of the balloon, these chains are stretched almost to their limit and very far apart. The piercing is too much for the stretched chains and they break apart., and the balloon pops.
Source:
In its relaxed state rubber consists of long, coiled-up polymer chains that are interlinked at a few points. Between a pair of links each monomer can rotate freely about its neighbour. This gives each section of chain leeway to assume a large number of geometries, like a very loose rope attached to a pair of fixed points. At room temperature rubber stores enough kinetic energy so that each section of chain oscillates chaotically, like the above piece of rope being shaken violently.
Source:
Kottayam District of Kerala is the leader in rubber production among the states of India. The rubber plant is not a native plant of India. Dutch colonialists who ... cultivated rubber in their plantations in Indonesia introduced the rubber plant to Kerala, India, because of its similar tropical climate.
Source:
EarSet 3 is crafted from anodized aluminum and hard rubber, making it flexible and very durable. These robust and scratch-free materials combine quality and comfort with state-of-the-art design. EarSet 3 comes equipped with a specially designed leather carrying case.
Source:
MORE ABOUT
United States