Chloroform Extract of Reclaimed Rubber

Abstract

Abstract 1. For any given reclaim, increased chloroform extract means greater softness and plasticity, but different types of reclaim with equivalent chloroform extracts may have widely different plasticities, or with the same workability may have widely different chloroform extracts. 2. While longer time of heat treatment at a given temperature increases the chloroform extract, increased temperature raises it decidedly. At elevated temperature (263° C) there is a transformation of chloroform-soluble into acetone-soluble material. 3. Within practical operating temperature limits, the milling and straining operations do not affect the chloroform extract. Increased number of passes through a refiner increases the chloroform extract. This fact is of importance in the chloroform determination. Cool refining gives a product with higher chloroform extract than hot refining. 4. The chloroform extract is unaffected by slow or rapid cooling of finished reclaim slabs. The slow-cooled reclaim, however, is somewhat drier and nervier. 5. Reclaimed rubber has a lower chloroform extract after natural aging than when freshly made. The aging process is also accompanied by an increase in the nerve and a decrease in the tackiness of the reclaim. 6. The use of oils as plasticizers in preference to excessive heat plasticization is not detrimental to reclaim quality, but is often desirable in producing many types of reclaimed rubber. 7. The percentage of chloroform extract present in typical commercial reclaims usually lies between 30 and 40 per cent, based on the rubber content. Values below 20 per cent indicate a low degree of devulcanization. Values above 50 per cent are rare but, when they do occur, indicate an excessive devulcanization. The amount of chloroform extract is an insensitive criterion of workability. Since a high chloroform extract does not indicate improved quality, a performance test must be used.