Rubber Recycling: Chemistry, processing, and applications

Abstract

For both environmental and economic reasons, there is broad interest in recycling rubber and in the continued development of recycling technologies. The use of postindustrial materials is a fairly well-established and documented business. Much effort over the past decadehas been put in to dealing with of end-of-life tires from landfills and vacantfields. It is only in the last few years that more business opportunities for recycled rubber have come to the forefront. Reclaiming rubber has gained increasing interest, more so in Europe than in North America. In those areas, much work has been done to refine the processes used. The major form of recycled rubber is still ground rubber. This is produced either by cryogenic, ambient, or wet grinding. The material is then used neat with sulfur/curatives, binders, or cements. The binders are normally moisture curable urethanes, liquid polybutadienes, or latex to produce items such as mats, floor tiles, and carpet undercushion. Recycled rubber is still used as tire derived fuel, but less so than 10 yearsago. Another outlet is as an additive to asphalt. Recycled rubber can be used in the plastics industry, for which much development is being done. Large particle size ground rubber or chips are used in civil engineering applications, landscaping, or artificial turf. Interms of applications, most use is outside of the conventional rubber industry. Cost factors are still addressed in the tire industry. As of 2012, approximately 8-10% recycled material is used in tires. The biggest obstacles to further adaption are safety factors and property loss. Better methods are needed for treating or modifying the rubber surface and for regenerating the rubber through devulcanization. Devulcanization gives the highest quality recycled materialinterms of processing and properties. However, short comings to devulcanization are reduced process safety and odorous chemicals that are required at present.