Figure 6. (A) E’(⎤) and (B) E”(⎤) curves for cellulose acetate (CA) and cellulose acetate nanofibers with annatto extract (CA@A) samples.
Adding annatto to CA causes reductions in both E’(⎤) and E”(⎤) throughout the broadband frequency range. When frequency tends to zero, E’ is known to tend to E (the static modulus). For example, at 10 Hz E’(⎤) was 0.32277 GPa for the CA sample and 0.21148 GPa for the CA@A sample; in other words, adding annatto extract to CA reduced the storage modulus by 34.48%. The loss modulus at 10 Hz E”(⎤) was 0.00952 GPa for the CA sample and 0.00826 GPa for the CA@A sample, a reduction of 13.26%. This effect is usually seen when plasticizers are added to a polymer mass [42]. This suggests that annatto acted similar to a plasticizer, reducing interactions between the molecules and this leading to fewer entanglements and increased molecular motion, in turn generating greater deformation and a lower modulus.