Photochemical surface modification of PET by excimer UV lamp irradiation

• Published in: Applied physics. B, Lasers and optics Vol. 81; no. 5; pp. 681 - 690
• Main Authors: GAO, S. L, HÄSSLER, R, MÄDER, E, BAHNERS, T, OPWIS, K, SCHOLLMEYER, E
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01.09.2005
• Subjects: Chemistry; Crosslinking; Exact sciences and technology; Excimers; General and physical chemistry; Irradiation; Lamps; Media; Photochemical; Photochemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Polyethylene terephthalates; Polymers; Ethylene terephthalate polymer; Atomic force microscopy; Photochemical crosslinking; Photochemical method; Mechanical properties; Polymer; Laser irradiation; Experimental study; Potassium chloride; Surface treatment; Metal vapor lamp; Ultraviolet radiation; Ultraviolet irradiation; Excimer; Surface properties; Photoelectron spectrometry
• ISSN: 0946-2171; 1432-0649
• DOI: 10.1007/s00340-005-1928-9

UV irradiation has interesting potential for the photochemical modification of polymers. In order to study cross-linking effects and/or thin-layer deposition following a treatment in the presence of bi-functional media or in inert atmosphere, irradiation of PET in various atmospheres was performed using a KrCl excimer lamp. Surface properties were investigated by atomic force microscopy, nanoindentation, micro-thermal analysis, and X-ray photo-electron spectroscopy. The studies reveal that surface chemical composition, morphology, adhesion, thermomechanics, and stiffness/modulus are strongly affected by UV irradiation in the presence of bi-functional media. Films treated in octadiene and argon show an increase of surface modulus, much less expansion, and lower soft/melt temperatures, which is an indication of the surface cross-linking effect and a decrease of crystallinity within the near-surface layer. In the case of a diallylphthalate-treated film, depending on the local structure, either a strong decrease of melting temperature or no melting point is found, which is attributed to the irregular cross linking and thickness of the modified layer associated with a decrease of surface modulus. A significant increase of the alkali resistance is found after irradiation, as a result of both wetting and cross-linking effects on the polymer surface.