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Recycling in the Form of a Filled Polymer
This is the main form of filler recycling in operation today and is likely to remain the preferred option where the polymer itself is readily recycled. Why go to the trouble and expense of separating the filler, only to have to reintroduce it later?
The main fillers recycled in this way are carbon black (in elastomer compounds), talcs (in polyolefins), and carbonates (in PVC compounds).
Carbon Black Recycling in Elastomer Compounds
The recycling of the fillers themselves has been discussed earlier. This section deals with the case where the rubber compound containing the carbon black is recycled.
The global tire industry currently produces over 1.5 billion tires each year, containing over seven million tons of carbon black fillers, and the global demand is expected to grow at a rate of 4.1-4.5% (CAGR) over the period 2012-2019, largely driven by growth of demand in the BRIC economies plus Eastern Europe. There is thus great incentive to recycle end of life tires, especially closed loop recycling.
The main problem for tires and also rubber in general is its cross-linked nature; unlike thermoplastics, most rubbers cannot be reprocessed in the same way as the virgin material unless the cross-links are broken, and this is a difficult process. Despite this, rubber recycling by devulcanization is being actively pursued as well as by the simpler method of size reduction. The various approaches being pursued for tires are briefly described below. The same processes can be easily adapted to other carbon black-containing elastomeric products.
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