Ultrasonic devulcanization

Isayev, A.I., Continuous ultrasonic devulcanization of vulcanized elastomers, US Patent, 5,258, 413, 1993. 

Isayev, A.I. Kim, S.H. Yushanov, P. Ultrasonic devulcanization of SBR rubber experimentation and modeling based on cavitation and percolation theories. Rubber Chem. Technol. 1998, 71, 168. 

Boron, T. Klingensmith, W. Roberson, P. Ultrasonic devulcanization of tire compounds. Tire Technol. Int. 1996, 82-84. 

Ultrasonic devulcanization, therefore, causes significant degradation of polymer chains. A simple model based on a purely topological consideration was proposed and simulation of the process was carried out. In the model they have assumed a breakup... 

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. 

Tapale, M. Isayev, A.I. Continuous ultrasonic devulcanization of unfilled NR vulcanizates. J. Appl. Polym. Sci. 1998, 70, 2007. 

Yushanov, S.P. Isayev, A.I. Levin, V.Yu. Percolation simulation of the network degradation during ultrasonic devulcanization. J. Polym. Sci. Phys. Ed. 1996, 34, 2409. 

Under the license from the University of Akron for the ultrasonic devulcanization technology, NFM Co. of Massillon, Ohio, has built a prototype of the single-screw extruder for ultrasonic devulcanization of tire and rubber products (Boron et al., 1996 Boron, 1999). It was reported that retreaded truck tires containing 15 wt.% and 30 wt.% of ultrasonically devulcanized carbon black-filled SBR had passed the preliminary dynamic endurance test (Boron, 1999). 

Extensive studies on the ultrasonic devulcanization of rubbers and some preliminary studies on ultrasonic decrosslinking of crosslinked plastics were... 

FIGURE 15.7 The stress-strain curves for unfilled NR vulcanizates prepared from ultrasonically devulcanized NR in coaxial reactor at various flow rates and amplitudes at a die gap of 2.54 mm and a barrel temperature of 120°C. 

Ultrasonic devulcanization also alters revulcanization kinetics of rubbers. It was shown (Isayev et al., 1996b) that the revulcanization process of devulcanized SBR was essentially different from those of the virgin SBR. The induction period is shorter or absent for revulcanization of the devulcanized SBR. This is also true for other unfilled and carbon black-filled mbbers such as GRT, SBR, NR, EPDM, and BR cured by sulfur containing curative systems, but not for silicone rubber cured by peroxide. It was suggested that a decrease or disappearance of the induction period in case of the sulfur-cured rubbers is due to an interaction between the rubber molecules chemically modified in the course of devulcanization and unmodified rubber molecules resulting in crosslinking. It was shown that approximately 85% of the accelerator remained in the ultrasonically devulcanized SBR rubber (Levin et al., 1997a). 

Ultrasonically devulcanized rubbers consist of sol and gel. The gel portion is typically soft and has significantly lower crosslink density than that of the original vulcanizate. Due to the presence of sol the devulcanized rubber can flow and is subjected to shaping. Crosslink density and gel fraction of ultrasonically devulcanized rubbers were found to correlate by a universal master curve (Yushanov et al., 1996, 1998 Diao et al., 1999). This curve is unique for... 

In search for a more economical process for recycling used tires, the ultrasonic devulcanization technology was further investigated to develop a feasible process to minimize the stockpiles of waste tires. This process induces the cleavage of the chemical networks through the combination of ultrasonic and chemical devulcanization (Kim et al., 2003). According to authors, the products from devulcanization of tires are carbon black and extended oil that can be used in many applications. A claim was also made that the technology can separate sulfur. 

Recently, ultrasonic devulcanization of tire rubbers was carried out in the presence of ozone (Lee et al., 2009a). This extruder was similar to the coaxial ultrasonic extruder depicted in Figure 15.3a. It was shown that by using treatment by ultrasound and ozone combination the mechanical properties of revulcanized rubbers were improved. 

Recently, a novel continuous process has been developed for devulcanization of rubbers as a suitable way to recycle used tires and waste rubbers [83-119]. This technology is based on the use of high-power ultrasounds. The ultrasonic waves of certain levels, in the presence of pressure and heat, can quickly break up the three-dimensional network in crosslinked rubber. The process of ultrasonic devulcanization is very fast, simple, efficient, and solvent and chemical free. Devulcanization occurs at the order of a second and may... 

Extensive studies on the ultrasonic devulcanization of rubbers and some preliminary studies on ultrasonic decrosslinking of crosslinked plastics were carried out [83-122]. It was shown that this continuous process allows one to recycle various types of rubbers and thermosets. As a most desirable consequence, ultrasonically devulcanized rubber becomes soft, therefore making it possible for this material to be reprocessed, shaped, and revulcanized in very much the same way as the virgin rubber. This new technology has been used successfully in the laboratory to devulcanize a ground tire rubber (GRT)... 

Ultrasonically devulcanized and ground-carbon black (CB)-filled NR was blended with virgin CB-fiUed material. Figure 11 gives the tensile strength of these NR-NR blends containing 35phr CB [137]. The blends of devulcanized... 

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