## 3 Results and Discussion
### Curing Behaviors of Halogenated Elastomers with Metal Oxide and MF  
It is well-known that halogenated elastomers such as CR and BIIR can be cured with metal oxides. Represented in Figure 3a,b are the curing behaviors of CR and BIIR as per the formulations given in the mixes 3-6. Their cure characteristics are displayed in Table 2.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Mix ID** & \(\mathbf{M_{L}}\) & \(\mathbf{M_{H}}\) & \(\mathbf{\Delta M}\) & \(\mathbf{T_{52}}\) & \(\mathbf{T_{90}}\) & **CRI** \\  & **(dNm)** & **(dNm)** & **(dNm)** & **(min)** & **(min)** & **(min)** & **(min\({}^{-1}\))** \\ \hline NR-CV & 0.96 & 5.73 & 4.77 & 1.95 & 3.88 & 51.81 \\ NR-CV-MF\({}_{3}\) & 0.77 & 6.64 & 5.87 & 2.32 & 6.86 & 22.02 \\ CR-ZnO & 0.74 & 4.90 & 4.16 & 6.26 & 43.83 & 2.66 \\ CR-ZnO-MF\({}_{3}\) & 0.64 & 10.14 & 9.50 & 2.18 & 37.25 & 2.85 \\ BIIR-ZnO & 1.20 & 2.53 & 1.33 & 10.64 & 13.92 & 30.48 \\ BIIR-ZnO-MF\({}_{3}\) & 1.24 & 4.89 & 3.65 & 2.71 & 8.89 & 16.18 \\ NR/CR-CV & 0.64 & 3.91 & 3.27 & 3.08 & 15.18 & 8.26 \\ NR/CR-CV-MF\({}_{3}\) & 0.53 & 6.41 & 5.88 & 2.92 & 22.36 & 5.14 \\ NR/BIIR-CV & 0.87 & 2.66 & 1.79 & 4.97 & 9.95 & 20.08 \\ NR/BIIR-CV-MF\({}_{3}\) & 0.82 & 5.87 & 5.05 & 3.10 & 18.05 & 6.68 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Cure characteristics of the mixes at 170 \({}^{\circ}\)C, 1 h.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Mix ID** & **Reversion (\%)** \\ \hline NR-CV & 25.8 \\ NR-CVMF\({}_{3}\) & 7.5 \\ NR/CR-CV & 3.83 \\ NR/CR-CVMF\({}_{3}\) & No reversion \\ NR/BIIR-CV & 7.9 \\ NR/BIIR-CVMF\({}_{3}\) & No reversion \\ \hline \hline \end{tabular}
\end{table}
Table 3: Reversion in compounds at 170 \({}^{\circ}\)C.  
CR with metal oxide (ZnO/MgO) exhibit a marching modulus curing behavior with a high induction period (\(T_{S2}\) = 6.26 min) and time to optimum cure (\(T_{90}\) = 43.8 min). Similar behavior was also observed during the curing of BIIR with ZnO. Here also the induction period was very high (\(T_{S2}\) = 10.6 min). However, the curing of BIIR with ZnO exhibits a plateau type curing behavior. As a result, the \(T_{90}\) (13.9 min) of BIIR/ZnO was relatively low compared to CR/ZnO/MgO. It is interesting to note that the curing efficiency of ZnO in both the CR and BIIR becomes enhanced after incorporating 3 phr of MF. For instance, the extent of curing in terms of \(\Delta\) torque in CR-ZnO has been improved by about 144% with the addition of 3 phr MF (CR-ZnO/MF\({}_{3}\)). Similarly, the \(\Delta\) torque in BIIR/ZnO was improved by around 174% in the presence of 3 phr MF. Moreover, the induction period, \(T_{S2}\) of CR-ZnO has economically been reduced from 6.3 min to 2.2 min, and for BIIR/ZnO, it is reduced from 10.6 min to 2.7 min, respectively, after adding 3 phr MF. Literature reported that the halogenated rubbers such as CR and BIIR can also produce conjugated dienes when it is heating with ZnO [23; 24]. Hence, the efficiency in the curing reaction between CR and BIIR with ZnO in the presence of MF can also be ascribed to the Diels-Alder reaction between the in situ formed dienes generated on the polymer with the maleimide moieties of MF [25; 26; 27].