Laser treatment on synthetic fibres

Abstract

Laser irradiated materials, such as semi-conductors, metals and dielectrics have characteristic morphological features on the surface. Similar features are found on synthetic polymeric materials irradiated by excimer lasers. After laser irradiation, certain synthetic fibers develop characteristic roughness in the form of granular or ripple like structures on the originally smooth surface. The structures can be generally classified according to the irradiated laser fluence into two streams, namely high-fluence laser treatment (laser power above the ablation threshold of the irradiated materials) and low-fluence laser treatment (laser power below the ablation threshold of the irradiated materials). The structures produced by both kinds of laser treatment also depend on the nature of materials and laser parameters, such as fluence, dosage, wavelength and sometimes the polarization. In this report, poly (ethylene terepthalate, PET) and polyamide (Nylon) textile fibers and fabrics were used in the investigation. These samples were irradiated by excimer UV lasers of two different wavelengths, 193 nm and 248 nm. After irradiation,the fibers or fabrics were studied with different methods in order to find out the property changes due to laser processing. Surface morphological change was observed with scanning electron microscopy (SEM) and atomic force microscopy (AEM). Based on the results, the relationship between laser parameters and the surface morphology was obtained in terms of roughness, mean ripple spacing, etc. For high fluence irradiation, the ripple spacing has the order of microns and the pattern is perpendicular to the fiber axis, i.e. the direction of the fiber frozen-in tension. In low fluence laser treatment, the ripple/granular structures induced on the surface have spacing mainly around 200 nm. Furthermore, there is a narrow window of low energy fluence beyond which no structuring can be formed. These and other differences in characteristics and the under pinning mechanisms were investigated in this project. In addition to physical measurements, chemical modifications due to laser treatment were also studied in this project. X-ray photo electron spectroscopy (XPS) and Fourier transform infrared spectrascopy (FTIR) were used to analyze the changes of the chemical composition of the laser irradiated surface. Again, these results reveal some significant difference between high and low fluence laser treated PET. The O/C ratio of the treated surface decreases in high fluence laser treatment, but increases in low fluence treatment. This can provide a simple chemical explanation for some modified properties observed. Changes in textile properties as a result of surface modification due to the irradiation of excimer lasers were subsequently studied. Surface luster, wettability, dyeability and stability of the treated fabrics were investigated in this project. These investigations give useful information for further study and may lead to some potential applications in textile industry.