## 3 Results and Discussion
The characteristic solid tangential line represents the determination of [PERSON]'s modulus for the UV light-affected sample. The intersection of the dashed line with the experimental curve at a 0.2% strain offset provides the yield stress (\(\sigma_{y0.2}\)). \begin{table}
\begin{tabular}{c c c} \hline \hline  & \multicolumn{2}{c}{**Virgin FEP**} & \multicolumn{2}{c}{**Heat-Treated FEP**} \\ \cline{2-3}
**N** & \(\textbf{F_{th}(N), J/cm^{2}}\) & \(\textbf{F_{th}(N), J/cm^{2}}\) \\ \hline
20 & 9.36 & 1.05 \\
30 & 7.84 & 0.88 \\
50 & 5.98 & 0.70 \\
100 & 4.28 & 0.51 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Ablation thresholds \(F_{\text{th}}(N)\) of FEP polymer for a different number of laser pulses per spot. Laser parameters: \(\tau_{\text{p}}\sim\)10 ns, \(\lambda=355\) nm, and \(f_{\text{rep}}\approx 20\) kHz. Figure 6: Multi-pulse incubation behavior of the FEP polymer: (**a**) virgin, (**b**) heat-treated. Accumulated laser fluence \(N\times F_{\text{th}}(N)\) versus number of laser pulses per spot \(N\). Solid symbols—experimental data points; solid lines—fit by Equation (2). Laser parameters: \(\tau_{\text{p}}\sim\)10 ns, \(\lambda=355\) nm, and \(f_{\text{rep}}\approx 20\) kHz. [PERSON]'s modulus and yield stress values are summarized in Table 2. From the experimental stress-strain curves, it can be observed that the FEP samples had a linear elastic behavior below strains of 1.5%. Extrapolating linear elastic parts of the experimental stress-strain curves of virgin FEP-1 samples with two different cutting directions of the polymer, we found mean Young's modulus values of 583.92 \(\pm\) 0.23 MPa and 589.46 \(\pm\) 0.21 MPa and mean yield stress values of 11.60 \(\pm\) 0.10 MPa and 12.17 \(\pm\) 0.07 MPa for samples cut parallel and perpendicular to the FEP roll direction, respectively. [PERSON]'s modulus and yield stress of heat-treated FEP films (FEP-2) with different cutting directions decreased slightly from 555.57 MPa to 511.19 MPa, and from 10.92 MPa to 10.36 MPa, respectively. The changes in mechanical properties, as well as differences in [PERSON]'s modulus and yield stress for the two different cutting directions of the heat-treated FEP samples, could be associated with an increase in the anisotropy of the films. Certain rearrangements of the material material in the sample, which is not the case for the FEP samples, are not the case for the FEP samples. Figure 8: Stress-strain curves for FEP samples cut perpendicular to the roll direction: virgin (FEP-1) a well as heat (FEP-2)-, UV light (FEP-3)-, and heat–UV (FEP-4)-affected films. Figure 7: Stress-strain curves for FEP samples cut in parallel to the roll direction: virgin (FEP-1) as well as heat (FEP-2)-, UV light (FEP-3)-, and heat–UV (FEP-4)-affected films. polymer chains caused a slight reduction in the fraction of crystalline polymer components from 31.86% to 31.07% (see Figure 2a,b). UV light-treated FEP films (FEP-3) showed a moderate increase in the fraction of crystalline components (43.54%), Young's modulus (651.88-665.52 MPa), and yield stress (12.89-13.31 MPa) for both cutting directions. The increase in the fraction of the crystalline component and the decrease in anisotropy could be associated with the generation of radicals and the oxidation of tertiary carbon, which is bonded to the perfluoromethyl group responsible for the amorphicity of the FEP film. As the crystalline regions in the polymer became more refined, the possibilities for stress concentration in less cohesive amorphous regions significantly decreased, which led to enhanced mechanical properties compared to those of the more amorphous polymer. The decrease in crystalline component fraction (28.08%), Young's modulus (408.62-499.11 MPa), and yield stress (8.39-9.69.MPa) of heat-UV-treated FEP films (FEP-4) for both cutting directions could be due to polymer chain rearrangement, which is a complex function of combined treatment.