Evaluation of Waste Tire Devulcanization Technologies

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  • Topic: Synthetic rubber, Rubber, Polymer
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Feb.2011 - M.S. Laura Fontana - Centerplastics Enterprise, Ltd Eastern Industrial Road, zip. 516127, Shiwan Town, Boluo Area, Huizhou, DongGuan, GuangDong, P.R.China
Chapter 1 - Introduction
Approximately 25 potential devulcanization technology researchers and developers were identified throughout the world, however, only a very small number of devulcanization systems are now operating. These are primarily small-capacity systems, which are devulcanizing natural or synthetic rubbers (as opposed to devulcanizing the mixture of rubbers recovered from waste tires).

The general types of devulcanization technologies identified and analyzed in the study are shown below.
Technology Basis of Processing Zone of Reaction
Chemical Chemicals/chemical reactions Surface of particles
Ultrasonic Ultrasonic waves Throughout particles
Microwave Microwaves Throughout particles
Biological Microorganisms Surface of particles
Other Mechanical
Surface of particles
Key findings
· Reliable information and data on devulcanization of waste tire rubber are difficult to obtain due to proprietary claims, efforts to hide poor or infeasible process performance and product quality, and the limited number of technology researchers and developers and of peer-reviewed data. Reliable data relating waste tire characteristics, devulcanized rubber quality, end product performance, and production costs is scarce. · Only a very small number of low-capacity devulcanization systems are operating in the United States (at approximately 50 Kg /hr, all R&D scale, mechanical, or ultrasonic). No proven commercial capacity units could be found that are currently devulcanizing waste tires, for example, at 500 Kg/hr or greater. The likely reasons include insufficient product quality and high costs of production. · In terms of the potential of producing high-quality devulcanized rubbers (for example, high strength), the best technology appears to be ultrasonic, based on the current state of the art.

· Devulcanization of single rubbers has much more history than that of multi-rubber mixtures such as waste tires. Only a few companies devulcanize single formulation rubber as a result of captive conversion or merchant scrap recovery from manufacturing. The production of devulcanized rubber from home manufacturing scrap in the U.S represents about 1 to 2 percent of total U.S. rubber consumption. · The quality of devulcanized single rubbers is higher than that of devulcanized multiple rubbers.

· Devulcanization that depends on surface devulcanization technologies (for example, chemical and mechanical) appears destined in the near term to produce low- or medium-quality devulcanized rubber material.

· The estimated cost for producing devulcanized materials from waste tires is $0.3 to $0.6/Kg ± 30 percent, if including the cost of crumb rubber feedstock. This range of production costs is significantly greater than that of virgin rubbers. A typical tire compound contains the following constituents: Table 1. Composition of Tires

Passenger Tire Constituents Common Materials
Natural rubber 14% Natural rubber
Synthetic rubber 27% SBR, butadiene rubber
Carbon black 28% Carbon black
Steel 14%–15% Steel
Fabric, fillers,
antiozonants, etc.
16%–17% Polyester, nylon, aromatic oil, coumarine
resin, silica, bonding agent, stearic acid,
antioxidant, processing chemicals, sulfur,
zinc oxide
Truck Tire
Natural rubber 27% Natural rubber
Synthetic rubber 14% Synthetic rubber
Carbon black 28% Carbon black
Steel 14%–15% Steel
Fabric, fillers,
antiozonants, etc.
16%–17% Polyester, nylon, aromatic oil, stearic acid,
antioxidant, wax, processing chemicals,
sulfur, zinc oxide
Source: Rubber Manufacturers Association, 2004.
• Reclaiming is a procedure in which scrap tire rubber or vulcanized rubber waste is converted—using mechanical and thermal energy and chemicals—into a...
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