Low‐Temperature Rubber Devulcanization via Sulfate Removal Using Hypochlorous Acid and Novel Turbidimetric Analysis

ABSTRACT This study presents a novel approach to rubber devulcanization using a combination of hydrochloric acid (HCl) and hydrogen peroxide (H 2 O 2 ) as an alternative to traditional nitric acid‐based methods. The optimized process, utilizing HCl and H 2 O 2 relative to the rubber's weight, demonstrated superior sulfur removal compared to conventional nitric acid treatments. Notably, the H 2 O 2 :HCl combination achieved significant sulfur extraction, reducing SO 4 content by 0.00444 g at 120% w/w concentration. This process effectively restores rubber to a gummy state with minimal oxidation (17.95%), making it ideal for recycling applications. Sulfur removal was accurately measured using a newly developed turbidimetric barium test and confirmed through field emission scanning electron microscopy (FESEM) analysis, which revealed significant morphological changes. Additionally, this method resulted in significantly lower oxidation and nitration of devulcanized rubber compared to nitric acid, potentially allowing the material to be pressed and revulcanized into new products. Finally, gas chromatography–mass spectrometry (GC–MS) analysis of the sol fraction revealed that chain scissions led to the formation of various value‐added compounds. This study challenges the traditional indicators of devulcanization success.