Complete devulcanization of sulfur‐cured butyl rubber by using supercritical carbon dioxide

Abstract

Sulfur-cured butyl rubber was devulcanized completely in supercritical CO 2 by using diphenyl disulfide (DD) as a devulcanizing reagent. The optimum devulcanizing conditions were studied and the sol fraction of the reclaimed rubber obtained was up to 98.5%. The possible devulcanizing mechanism was investigated. Then, the sol component of reclaimed rubber was characterized by gel permeation chromatography, 1 H-NMR, and differential scanning calorimetry, and the reclaimed rubber was characterized by TGA. Because of the substitution of a large portion of allylic hydrogen by sulfurated functional groups during vulcanization, the signal of the olefinic proton shift. As a result of the numerous decreases in the active crosslinking sites and the remaining DD, reclaimed rubber could not be cured by sulfur. At last, the blends of virgin butyl rubber and different contents of reclaimed rubber were revulcanized and their mechanical properties investigated.

Devulcanizaiton of waste tread rubber in supercritical carbon dioxide: Operating parameters and product characterization

“…Firstly, generation of the radicals of DD and polymer were caused by heat. It is generally believed that the rubber polymer main chain could not be degraded below 300 C, while some scission of main chains might take place at crosslink sites at 200 C [12]. These two types of radicals would combine to form sol and then was separated from the crosslink network.…”

“…Kojima et al [10,11] reported that natural rubber (NR) and isoprene rubber (IR) had been devulcanized with diphenyl disulfide (DD), in which process scCO 2 caused the swell of rubber and facilitated the permeation of DD into crosslink matrix. Butyl rubber (IIR) was completely devulcanizaed in scCO 2 by Jiang et al [12], with the sol fraction reached up to 100%. There is a certain amount of carbon black as filler in tires, but it does not interfere with the devulcanizing process [13,14].…”

Effect of Temperature on Devulcanization of Waste Sidewall Rubber by Supercritical Ethanol

“…The radicals had an instinctive tendency to couple and then form macromolecular structure fragments, which was the main compositions of sols. 43 On the other hand, the reaction activity of supercritical ethanol enhanced. As a result, the crosslinked structure broke rapidly and the sols increased sharply, with the unexpected occurrence of the main chain scission.…”

Review of the Reclaiming of Rubber Waste and Recent Work on the Recycling of Ethylene–propylene–diene Rubber Waste

“…Other miscellaneous methods such as devulcanization in supercritical carbon dioxide are also available but are not yet of industrial importance. 69 Reportedly, Guangming et al 70 succeeded to devulcanize waste rubber by T. ferrooxidants microbe (Fig. 8).…”