Supercritical fluid devulcanization

Chemical processes have been known for many years but are either ineffective in selectively cleaving cross-links or commercially not viable. Recent developments may eventually provide a true devulcanization process that is commercially viable. These include ultrasonic devulcanization, biotechnological devulcanization, and supercritical fluid devulcanization. 

Recycle Today there is a great emphasis on devulcanization methods to recycle the rubber in tires and other rubber products. Some of these new devulcanization methods use supercritical fluid technology, ultrasonic techniques, microwave energy, and biological modification.f These methods are explained in detail in the entry, which deals primarily with devulcanization. 

This article will review the classical chemical methods of devulcanization and their inherent limitations. The newer methods of devulcanization currently under development will also be reviewed. These include devulcanization using microbes, microwave, ultrasonically induced devulcanization, and devulcanization using supercritical fluids. 

The seventh trend is the increasing use of novel processing methods. For example, there is growing use of supercritical fluids (e.g., supercritical carbon dioxide and nitrogen gases) to foam polyolefin blends for density reduction. There is use of ultrasound to, for example, devulcanize cross-linked rubber. There is use of solid-state shear mechanical processing to break the polyolefin blend material into submicron particles to make environment friendly (water-based) polyolefin dispersions. There is use of electrospinning technique to make polyolefin fibers and in particular nanofibers. 

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