2. Faculty of Dentistry, King AbdulAziz University, Kingdom of Saudi Arabia.
End-of-life tires constitute one of the biggest environmental concerns in terms of environmental pollution and resources conservation. This study aims to determine the best proportion of reclaimed rubber and crumb rubber to be added as part of the constituents used in the manufacturing of three different tire parts (tread, side wall, and inner liner) in order to produce standard products from a mix of both recycled and original ingredients. Batches were prepared into which reclaimed rubber and crumb rubber were added to the formulation of three different tire parts, in addition to one batch as reference according to the original formulation. Batches were analyzed according to national and international standards to select the optimum percentage that can be introduced in new tire formulation preparations. Results revealed that reclaimed rubber could be used as 15 parts per hundred rubber (phr) in radial tread compound and as 25 phr in either radial side wall or radial inner liner compounds. As for crumb rubber, results showed that it could be used as 10, 20 and 25 phr in radial tread, radial side wall or radial inner liner compounds respectively. Incorporating higher amounts of either reclaimed or crumb rubber would lead to violating the standards specified in vulcanized rubber tension property test and in oscillating disk cure meter test. Savings in raw material and in energy resulting from the use of reclaimed rubber was calculated: As concerns raw materials, adding 15 phr reclaimed rubber to the tread formulation would save about 7.7% of each of Styrene Butadiene Rubber (SBR), Polybutadiene and carbon black. Adding 25 phr reclaimed rubber to the side wall formulation would save about 12.8% of each of natural rubber, Polybutadiene and carbon black. Adding 25 phr reclaimed rubber to the inner liner formulation would save about 13% of each of natural rubber, SBR and carbon black. Regarding energy conservation, use of reclaimed rubber in new tires would result in a total energy conservation of 6393GJ/year. In addition to the raw material and energy conservation, the process was found to be cost-effective.
Keywords: Crumb rubber, inner liner, reclaimed rubber, side wall, tire recycling, tread