## 3 Results and Discussion
Conversely, the decrease in anisotropy after UV exposure is likely due to photochemical processes, such as radical generation and the oxidation of tertiary carbons linked to the perfluoromethyl groups, which disrupt the polymer chain alignment and hinder the formation of a strongly oriented structure, leading to a more isotropic state despite a potential increase in the overall crystalline fraction. Nanosecond pulsed UV laser irradiation was used in order to determine the influence of heat treatment on the ablation parameters of FEP films. The crater diameter of laser-ablated polymers was analyzed using an optical microscope. The key ablation differences between the virgin (FEP-1) and heat-treated (FEP-3) polymers can be seen in Figure 4.  
Taking into account Equation (1) with the various pulse energy values, an ablation threshold fluence \(F\)th is obtained from a semi-logarithmic plot of the diameter squared of the ablated area \(D^{2}\) versus peak laser fluence \(F_{0}\). The slope of the straight lines provides the Gaussian beam radius \(w_{0}\). Figure 5 shows experimental results of the squared diameters \(D^{2}\) of ablated areas versus laser fluence \(F_{0}\) for laser-processed FEP polymers considering a different number of pulses per spot (\(N=5\), 10, 20, 30, 50, and 100). Figure 1: X-ray diffraction patterns with deconvoluted amorphous and crystalline components: (a) FEP-1; (b) FEP-2; (c) FEP-3; (d) FEP-4. Figure 2: Calculated pole figures for crystalline component reflex: (**a**) FEP-1; (**b**) FEP-2; (**c**) FEP-3; (**d**) FEP-4. Figure 4: The optical microscope images of nanosecond pulsed laser treatment of the FEP polymer: (**a**) virgin and (**b**) heat-treated. Laser parameters: \(\tau_{\rm p}\sim\)10 ns, \(\lambda=355\) nm and \(f_{\rm rep}\approx 20\) kHz, \(N=100\) pulses per spot, pulse energy \(E_{\rm p}=50\) μJ. Figure 5: Nanosecond pulsed laser treatment of FEP polymer: (**a**) virgin; (**b**) heat-treated. Squared diameters of the ablated areas of the FEP polymer in dependence on the peak laser fluence in the center of the Gaussian beam. Solid symbols—experimental data points; solid lines—fit by Equation (1). Laser parameters: \(\tau_{\rm p}\sim\)10 ns, \(\lambda=355\) nm, and \(f_{\rm rep}\approx 20\) kHz. Figure 3: Power spectra for pole figures at \(\psi=0^{\circ}\): (**a**) FEP-1; (**b**) FEP-2; (**c**) FEP-3; (**d**) FEP-4. Almost parallel lines with a fixed slope represent different modification thresholds for variant \(N\) due to the incubation phenomena. The extrapolation to \(D^{2}=0\) gives the modification threshold fluences presented in Table 1.  
The ablation threshold values decreased with an increase in the number of pulses. The threshold values were lower for the heat-treated FEP polymer by a factor of \(\sim\)10. Figure 6 shows a graph of the accumulated laser fluence \(N\times F_{\text{th}}(N)\) versus the number of pulses \(N\) for the FEP polymer. Potential sources of error in determining ablation thresholds include thermal accumulation, uncertainties in crater measurements due to polymer swelling or re-deposition, and deviations from an ideal Gaussian beam profile, which we estimated could lead to a 10% discrepancy between the calculated and actual ablation thresholds. However, the overall trends, including the decrease in threshold fluence with pulse number and differences between the virgin and heat-treated FEP, remained consistent with the established polymer ablation behavior. Virgin (FEP-1) as well as heat (FEP-2)-, UV light (FEP-3)-, and heat-UV (FEP-4)-treated 25 \(\upmu\)m thick FEP polymer samples of two different rolling directions were tested in the microctensile setup to determine [PERSON]'s modulus \(E\) (slope of the tangent to the stress-strain curve) and yield stress \(\sigma_{y0.2}\) (at 0.2% of strain \(\varepsilon\)). The average stress-strain curves for each FEP sample cut in parallel and perpendicular to the roll direction of the polymer are presented in Figures 7 and 8, respectively.