‐50 450 950 1450 1950 2450 -0.11 -0.09 -0.07 -0.05 -0.03 -0.01 0.01 0.03 Force (nN) Deflection (µm) Unexposed 24 hours 48 hours 72 hours 120 hours 144 hours 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 0 3 6 9 12 15 Young's Modulus (GPa) Radial Distance from the Center (µm) Nylon-unexposed 24 hours 48 hours 72 hours 120 hours 144 hours 3.2. Wide Angle X-ray and Infrared Analysis Figure 3: Typical force deflection diagrams of nanoindentation for nylon fibers of different UV exposure hours Figure 4: Variation of Young’s modulus values across the radius of nylon fibers for different durations of UV exposure 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 800 1300 1800 2300 2800 3300 3800 4300 Absorbance Wavelength (cm-1) Unexposed 24 hours 48 hours 72 hours 120 hours 144 hours Figure 5: FTIR spectra of UV exposed nylon fibers with UV exposure WAXS was performed on whole fiber to understand the changes of the fiber crystallinity. Figure 6 shows the WAXS images of UV exposed nylon fibers. Unexposed nylon diffractions are arced with some spots indicating the crystallinity and significant molecular orientation. Even at an ultraviolet exposure of 144 hours, the changes of diffraction arcs showed little noticeable difference. But the calculated percentage crystallinities using the ‘Polar’ software showed lower values for fibers with increased exposure times. The unexposed fibers were 70 % crystalline, which suggests that the fiber has more crystalline regions with high molecular orientation. So it can be reasonable assumed that the degradation may spread quickly to the crystalline areas making the deterioration of mechanical properties. When the UV exposure is further increased to 144 hours the crystallinity was reduced to 53 %. Fourier transform infrared spectroscopy was performed on fibers to understand the new formations of chemical bonds upon UV exposure. Figure 5 shows the infrared spectra obtained for fibers with different exposure duration. A broad range of peaks were observed corresponding to amide bonds. The significant observation is the formation of hydroxyl bonds (O-H) corresponding to wavelengths of 3300 – 3400 cm-1 with increase of exposure hours. The area of the hydroxyl peak was observed to increase through 144 hours of exposure. 232
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