*6.1.1.5 Coupling of NA-TVR-TPU-DMF treated PA-6,6*

**Figure 6** (z2) shows that amine group of TVR has related to both PA-6,6 and TPU, it seems the structural similarity (**Figure 11**). TVR has nitro group. Amino group of PA-6,6 and TPU may create a good color combination in NA-TVR-TPU-DMF when oxidized CBP has not been used in this process of coloration. For comparison, the reaction of oxidized carbon has been remarked with arrow sign connected with nitro group. In this coupling, there is no function of oxidized carbon due to missing of CBP in CM.
