Thermochemical devulcanization of natural rubber waste using CO2 and diphenyl disulfide: process optimization and analysis

TAO ZHANG; LUCIA ASARO; MICHEL GRATTON; NATHALIE POIROT; CAREN ROSALES; NOURREDINE AIT HOCINE

JOURNAL OF MATERIAL CYCLES AND WASTE MANAGEMENT

SPRINGER

Lugar: Berlin; Año: 2025

1438-4957

This paper presents a comprehensive study on the devulcanization of natural rubberindustry waste using supercritical CO2 as reaction medium and diphenyl disulfide asdevulcanizing agent, offering a sustainable solution to rubber recycling. Experimentswere conducted at 140 °C in a compression reactor to examine the effects of keyprocess variables, including diphenyl disulfide content, reaction time, and CO2 ratio, ondevulcanization performance. The resulting products were characterized using Horikxmodel, Fourier transform infrared spectrometry, thermogravimetric analysis, differentialscanning calorimetry, and scanning electron microscopy. Results revealed distincttrends: increasing diphenyl disulfide content enhanced devulcanization efficiency, whileprolonged reaction time and increased CO2 ratio exhibited non-linear effects. Notably,a reaction time of 40 min and a CO2 ratio of 10% were identified as optimal,maximizing devulcanization efficiency while minimizing undesirable materialdegradation. Under these conditions, with 5wt% diphenyl disulfide, the devulcanizationdegree and sol fraction reached 83.0% and 7.3%, respectively. The process primarilyinvolved sulfur bond scission and diphenyl disulfide grafting, further leading to sulfurand double bond formation in the sol fraction. These findings provide critical insightsinto optimizing selective devulcanization strategies and contribute to the advancementof environmentally friendly rubber recycling technologies.