Minggu, 08 April 2012

Reclaiming

The reclaiming procedure consists of two steps: The waste rubber is first chopped into pieces and ground into fine particles, known as crumb rubber. In the second step, the crumb is subjected to heat in the presence of chemicals and then followed by friction milling [14]. Reclaim was widely used in tire compounding for lower cost, improving processing and fatigue resistance. However, due the need for strength and abrasion resistance requirements, reclaim is not use in radial tires [37]. For the traditional rubber “reclaim,” crumb rubber is mixed with water, oil, and chemicals, and is then heated under pressure. During this process, the carbon-sulfur bonds are ruptured and the rubber becomes mostly devulcanized; it is then capable of being shaped into slabs [15]. According to Khait, tire manufacturers use these slabs as an alternative to virgin rubber for reuse in new tires or as an ingredient in other rubber products. Because reclaimed rubber has reduced elasticity, it is currently used for only about five percent of all new-tire production [15]. In the past, large quantities of whole tire tread peel, tubes, and other products were reclaimed using various reclaiming agents [6]. As much as 700 million pounds of reclaimed rubber was reported used in the U.S. in the 1950s [37]. When environmental regulations tightened and styrene-butadiene rubber (SBR) prices lowered, the result was an almost complete elimination of reclaim in the country [5]. The use of reclaim is primarily limited to bias ply tires [7]. At present there are two reclaimers in the U.S. These are U.S. Rubber in Vicksburg, Mississippi, and TRC in Stow, Ohio. There are reclaimers in the Netherlands, Russia, Romania, India, Mexico, Korea, and several other countries [37]. Reclaims are currently used in mats, bumpers, chocks, lowperformance tires, and other low-dynamic-stress rubber articles [37].

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