## 3 Experimental Analysis
### Analysis of Characteristics  
Next, we analyzed the mechanical properties and vulcanization characteristics resulting from the mixture design. Hardness, tensile strength, and elongation were analyzed as the mechanical properties; we analyzed the mixing-ratio-dependent vulcanization characteristics after measuring parameters T MAX, TC 10, and TC 90. The Cox response trace plot was used to analyze the results of the experiments performed based on the mixture design. The trace curves of the Cox response trace plots depict the effect of changing the ratio of the corresponding component along an imaginary line connecting the reference blend to a vertex. These curves are useful in cases where it is difficult to identify the response using contour or surface plots because the compound has four or more components. A short response trace points to a small proportion of the component. Further, the greater the effect of a component, the steeper the slope of the trace. Figure 1 shows the Cox response trace plots representing the mixture-ratio-dependent mechanical properties. Figure 1a depicts hardness as a function of the mixing ratio; we note that S exerts the greatest effect on hardness, followed by the accelerators DPG and TRA. Figure 1b shows the response trace plots for tensile strength, on which S again exerts the greatest influence, followed by TRA. Figure 1c shows the response trace plots for elongation; in this case, S strongly influences elongation, but in an inverse manner, contrary to the cases of hardness and tensile strength.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Division** & **Unit** & **Lower limit** & **1** & **2** & **3** & **4** & **5** & **Upper limit** \\ \hline DM & g & 2.02 & 2.03 & 2.25 & 2.26 & 2.49 & 2.76 & 3.03 \\ \hline TRA & g & 0.90 & 0.91 & 1.00 & 1.01 & 1.11 & 1.23 & 1.35 \\ \hline DPG & g & 1.86 & 1.87 & 2.08 & 2.08 & 2.30 & 2.58 & 2.80 \\ \hline BZ & g & 3.32 & 3.33 & 3.71 & 3.71 & 4.09 & 4.54 & 4.98 \\ \hline MBT & g & 0.55 & 0.56 & 0.62 & 0.62 & 0.68 & 0.76 & 0.83 \\ \hline S & g & 1.12 & 1.13 & 1.25 & 1.26 & 1.38 & 1.53 & 1.68 \\ \hline CMB & g & 990.22 & & & & & 985.33 \\ \hline Total & g & 1000.00 & & & & & 1000.00 \\ \hline \hline \end{tabular} DM, dibenzothiazyl disulfide; TRA, dipentamethylenethiuram tetrasulfide; DPG, diphenylguanidine; BZ, zinc di-n-butyl dithiocarbamate; MBT, 2-mercaptoethanolhizole; S, sulfur; CMB; carbon master batch.  
\end{table}
Table 1: Experimental design of mixtures.  
Figure 1: _Cont._Figure 2 shows the Cox response trace plots representing the mixture-ratio-dependent vulcanization characteristics. Figure 2a presents T MAX as a function of the mixing ratio; we note that S exerts the greatest effect on T MAX, followed by accelerator TRA. Figure 2b shows the Cox response trace plots for TC 10; in this case, BZ exerts the greatest effect on TC 10, followed by DM. Figure 2c shows the Cox response trace plots corresponding to TC 90, wherein we observe that TC 90 is most influenced by DPG and BZ.  
Figure 1: Cox response trace plots for mechanical properties depending on mixing ratio: (**a**) hardness; (**b**) tensile strength; (**c**) elongation.  
Figure 2: Cox response trace plots of vulcanization characteristics as a function of mixing ratio: (**a**) T MAX; (**b**) TC 10; (**c**) TC 90.