Effect of ultraviolet radiation on polytetrafluoroethylene: Morphology influence

The interaction between ultraviolet radiation and organic matter induces, via absorption mechanisms involving electronic transitions, degradation phenomena that drastically reduce the durability of the materials. According to its electronic configuration, polytetrafluoroethylene (PTFE) is a UV transparent semi crystalline polymer. However, when exposed to an excimer laser beam, PTFE is severely degraded. The damage results undoubtedly from an heterogeneous photothermal process. We found that the appearance of the degradation was notably affected by the microstructural state of the polymer; eg the crystalline morphology. We showed that the crystalline phase can act in several mechanisms of interaction: attenuation mechanisms, the activation of absorption sites is reduced by scattering of photons due to the semi crystalline nature of PTFE; initiatory mechanisms, the degradation is initiated in particular sites where photons are trapped owing to multiple reflections on the piles of lamellae.