In this study, the influence of the molecular structure of the rubber, the carbon black loading and de-vulcanization time and temperature on the thermo-chemical de-vulcanization efficiency of whole tire rubber was investigated by correlating sol fraction and crosslink density (Horikx-Verbruggen method). Differences in molecular structure influence the de-vulcanization mechanisms of rubbers as well as the efficiency. Increasing carbon black loadings result in higher crosslink densities due to a deactivation of the de-vulcanization aid. Variation of de-vulcanization temperature and time results in different degrees of heat accumulation in the rubber during de-vulcanization and thus leads to different de-vulcanization efficiencies.