Oscillatory measurement was performed under a constant axial load of 0.1 N to prevent wall-slip. Continuous relaxation time spectrum, H(τ), was calculated from the dynamic storage and loss moduli, G´(ω) and G´´(ω), by using the built-in non-linear regression functions of the rheometer software (Trios version 5.4.0.300). Relaxation modulus G(t) was obtained from H(τ). The highest G(t) value was normalized to 1, and a normalized G(t) over time was plotted.