*2.5. Mechanical Performance*

The tensile strength of prepared films was tested through an Instron 5566 tensile machine (Norwood, MA, US) with a stretch rate of 10 mm/min at room temperature. Three identical samples were tested and the average value of 5 samples was reported with a standard deviation.

The results belonging to the change in the breakpoint length besides the tensile strength are known by most researchers as a key factor in determining the degradation rate of polymeric compounds [49]. The below Equations (1) and (2) are applied to reach such information as follows:

$$\text{Retained elongation at break } (\varepsilon\_{\text{r}}) \, = \, \frac{\varepsilon\_{\text{t}}}{\varepsilon\_{0}} \tag{1}$$

$$\text{Retained tensile strength } (\sigma\_{\text{r}}) \, = \, \frac{\sigma\_{\text{t}}}{\sigma\_{0}} \tag{2}$$

In this respect, ε<sup>t</sup> and ε<sup>0</sup> are the change in the breakpoint length of samples with and without being exposed to UV at different time intervals, respectively. Similarly, σ<sup>t</sup> and σ<sup>0</sup> are the tensile strength of samples with and without being exposed to light at different time intervals.

To track the effect of degradation on the mechanical properties, the tensile strength of samples before and after the UV radiation was tested at different time periods at ambient temperature. For this purpose, all prepared films were cut into six pieces (5 cm × 1 cm) and each piece was placed under UV radiation up to 500 h and at each specific time interval, the tensile strength test was taken. The mechanical tests were accomplished on the samples without being exposed to UV radiation to make a better comparison.
