Reclaiming waste rubber

Workers in Sri Tanka [24] reclaimed waste rubber by utilising a readily available, low-cost and environmentally friendly amino compound and then carried out an extensive study comparing the properties of a compound produced by blending virgin NR with this reclaimed rubber at a ratio of 85 15 (designated Novel reclaim) with two other rubber compounds ... 

Further information in particular areas can be obtained by using recent reviews. For example, readers who would like to obtain more information on the use of waste rubber in blends with thermoplastics, thermosets and virgin rubber compounds can obtain it in an extensive review that has been produced recently by Karger-Kocsis, Meszaros and Barany [1], This review also surveyed the methods available to reclaim waste rubber, the surface treatment of rubber particles to improve interfacial adhesion in blends, and the principals underlying the compatibilisation of waste rubber within the host matrix. 

Addition of scrap rubber in the form of either ground waste vulcanizates or reclaim in rubber compounds gives economic as well as processing advantages. In addition to lowering the cost of rubber compounds, the use of cross-linked rubber particles has beneficial effects such as faster extrusion rate, reduced die swell, and better molding characteristics. 

The product resulting from the treatment of waste rubber (flash, used tyres, etc.) by heat and chemical agents, which effect sufficient break down and softening so that the reclaim may be used as a compounding ingredient in fresh compound without excessive degradation of physical properties. 

A number of methods [11,13-17] have been applied in an attempt to solve the problem and to find more effective ways of tire rubber recycling and waste rubber utilization. These methods include retreading, reclaiming, grinding, pulverization, microwave and ultrasonic processes, pyrolysis, and incineration. Processes for utilization of recycled rubber are also being developed, including the use of reclaimed rubber to manufacture rubber products and thermoplastic-rubber blends and the use of GRT to modify asphalt and cement. 

If rubber is incinerated to reclaim embodied energy then it can yield substantial quantities of useful power. In Australia, some cement factories use waste rubber as a fuel somce. 

In addition to the two reviews that are mentioned at the beginning of this section, a number of other relatively recent reviews of the processes and methods that have been developed and evaluated for the devulcanisation of waste rubber are available. For example, Majumdar published an overview in 2009 in the Chemical Weekly journal [4], which covered the challenges that face workers in this field and covered the main types of systems that have been developed (i.e., chemical, microwave, ultrasonic and so on). This article also covered the production and use of rubber crumb from waste rubber. In another article [5], Majumdar reviews the three main sources of reclaimed rubber that are available in the marketplace (rubber crumb, rubber powder and chemically digested reclaimed sheet) and describes their properties and uses. 

A devulcanisation process that has some similarities to the DeLink process has been published as a US patent by Tang (US 6590042). In this process, a specially designed twin-screw extruder is used, with the waste rubber in a crumb form, and a reclaiming agent that includes the following rubber compounds ... 

A more recent article that addressed the use of the DeLink process was published in Rubber Journal Asia [13]. It featured the Gujarat Reclaim and Rubber Products Company, which produces reclaimed rubber from both synthetic and NR waste, as well as a light-coloured reclaim from latex scrap using the Rubplast process. The company uses Green Rubber s patented devulcanisation agent, DeLink, at a ratio of two parts DeLink to 100 parts crumbed waste rubber, to produce a product that can be incorporated back into new rubber compounds. The article claims that this is very advantageous to the rubber industry as it enables them to re-use the 5-15% of waste, which they typically throw away. 

Nevada P., Baneqee T.S., Dutta B., Jha A., Naskar A.K., and Bhowmick A.K. Thermoplastic elastomer from reclaimed rubber and waste particles, J. Appl. Polym. Sci., 83, 2035, 2002. 

Matsushita et al. [127] prepared compositions showing good vulcanizability containing EPDM reclaim. Weather-strip wastes comprising of sulfur-cured EPDM mbber (containing 50% carbon black) were kneaded at 300°C and 3 MPa and extruded to give a rubber (Mw 200,000 gel content 65%), 25 parts of which was mixed with unvulcanized SBR 75, carbon black 37.5, and sulfur 1.3... 

For some applications, such as when it is necessary to dissolve or solvate rubbers, or rubber compounds to form doughs and solutions it is desirable to use a machine in this category. Various types of machines can be used to produce the required form. Grinders are also used to reduce scrap vulcanisate to form a rubber crumb for purposes of working this waste product back into cheap compounds, or prior to reclaiming rubber by chemical processes. 

Agency, "Rubber Reuse and Solid Waste Management", U.S. Government Printing Office, Washington, D.C., 1971, p. 48 (c) A. Nowry, Ed., "Reclaim Rubber, Its Development, Applications, and Future", Maclaren and Sons, London, 1962. 

In an attempt to reduce secondary pollution and protect the incinerators, the Tokyo Metropolitan Government, since 1973, has been asking households to separate some items from ordinary wastes before they are put out for collection. The items to be separately collected include those which cannot be burned, such as metals, glass and ceramics, and those which should not be burned, such as plastics, rubber, hides and leather. These items are buried in reclaimed lands, unprocessed. 

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