## 3 Results and Discussion
### ATR-FTIR Analysis  
The FTIR spectra of the HCRMB with different amounts of sulfur are presented in Figure 12 and the values of \(\rm I_{CA}\), \(\rm I_{Si\text{-}O\text{-}Si}\), and \(\rm I_{PB}\) are shown in Figure 13. \(\rm\Delta I_{CA}\) and \(\rm\Delta I_{Si\text{-}O\text{-}Si}\) are used to analyze the oxidation degree of RMB and the level of CR's desulfurization [28]. The difference between the \(\rm I_{CA}\) of unaged RMB and aged RMB is \(\rm\Delta I_{CA}\). \(\rm\Delta I_{Si\text{-}O\text{-}Si}\) is calculated by referring to \(\rm\Delta I_{CA}\). \(\rm\Delta I_{CA}\) and \(\rm\Delta I_{Si\text{-}O\text{-}Si}\) are presented in Tables 3 and 4. As shown in Figure 13a, the \(\rm I_{CA}\) of the HCRMB with different amounts of sulfur under RTFOT and PAV is less than that of the 70\(\rm\#\). In addition, according to Table 3, the \(\rm\Delta I_{CA}\) of the HCRMB with different amounts of sulfur after aging is lower than that of the 70\(\rm\#\), indicating that the oxidation degree of HCRMB with different amounts of sulfur is smaller than that of 70\(\rm\#\). The \(\rm\Delta I_{CA}\) ranking is 20 TB_0.25 ul \(<\) 20 TB_0.45 ul \(<\) 40 TB_0.25 ul \(<\) 40 TB_0.45 ul \(<\) 70\(\rm\#\) after RTFOT aging and the \(\rm\Delta I_{CA}\) ranking is 20 TB_0.25 ul \(<\) 20 TB_0.45 ul \(<\) 40 TB_0.25 ul \(<\) 40 TB_0.45 ul \(<\) 70\(\rm\#\) after PAV aging. This indicates that the carbonyl group of conventional RMB is less affected by aging than that of HCRMB and that sulfur cannot reduce the degree of oxidation of HCRMB after aging.  
Figure 11: CAI and PAI of HCRMB with different amounts of sulfur after PAV: (a) CAI and (b) PAI.  
Figure 10: CAI and PAI of HCRMB with different amounts of sulfur after RTFOT: (a) CAI and (b) PAI.  
Figure 12: ATR-FTIR spectra of HCRMB with different amounts of sulfur before and after aging.  
Figure 13: \(\rm I_{CA}\), \(\rm I_{Si-O-Si}\), and \(\rm I_{PB}\) of HCRMB with different amounts of sulfur before and after aging: (a) \(\rm I_{CA}\), (b) \(\rm I_{Si-O-Si}\), and (c) \(\rm I_{PB}\).  
Based on Figure 13b and Table 4, the I\({}_{\text{Si-O-Si}}\) ranking before aging is 20 TB_0.25 ul \(<\) 20 TB_0.45 ul \(<\) 40 TB_0.45 ul \(<\) 40 TB_0.25 ul, indicating compared to 70#, HCRMB with different amounts of sulfur has silica and the amount of silica in RMB increases as the amount of CR in RMB increases. The \(\Delta\)Isi-O-Si ranking after RTFOT and PAV is 40 TB_0.45 ul \(<\) 40 TB_0.25 ul \(<\) 20 TB_0.45 ul \(<\) 20 TB_0.25 ul, indicating under the influence of aging, conventional RMB is more easily desturized than HCRMB, and sulfur can inhibit the degree of desulfurization of HCRMB. Furthermore, as described in Figure 13c, compared to HCRMB with different amounts of sulfur, 70# had lower I\({}_{\text{PB}}\) values under unaged conditions, and the I\({}_{\text{PB}}\) ranking under unaged conditions was 20 TB_0.45 ul \(<\) 20 TB_0.25 ul \(<\) 40 TB_0.45 ul \(<\) 40 TB_0.25 ul, indicating that high content of CR leads to an increase in the polybutadiene polymer content of RMB. The I\({}_{\text{PB}}\) values of HCRMB with different amounts of sulfur decreases with aging, whereas in conventional RMB, there is an increase in I\({}_{\text{PB}}\) values during aging, suggesting that the aging process of HCRMB with different amounts of sulfur is dominated by the degradation of polybutadiene, whereas there is a certain CR desulfurization in conventional RMB aging [13].