UV-LIGHT CURING OF CURED IN PLACE PIPES (CIPP) WITH LEDS

摘要

UV-light curing of resins is well known in furniture and circuit board producing industries since the 1970ies. New photo catalysers for curing thicker layers enabled the UV-light curing of strong structural construction elements - first for light domes and since 1986 for CIPP. Up to now gas-discharge lamps are common for curing CIPP with UV-light.Since the early 1960ies LEDs have been developed within the last 40 years from only red-yellow colours into a bunch of different colours emitting LEDs with dramatically increasing luminous efficiency. LEDs with lower efficiency have been in use many years for coloured illumination effects. Now the increase of luminous efficiency during the last years allows engineers to use LEDs in a wide area of technical applications. LEDs for the blue and ultraviolet spectrum developed in the 1990ies allow a punctual cure of resin with UV-light at low temperatures. Since 2006 high efficiency LEDs are available with blue and UV-light spectrum and so the use of LEDs instead of gas-discharge lamps for curing CIPP became a theoretical alternative.This paper explains the curing mechanism when using UV-light generally and shows the differences and limits between gas-discharge lamps and LEDs. It also takes a critical look at the near future of LEDs in CIPP curing.