Price: 10.00
The application of ultraviolet )) curing is a growing field in furniture coating, because this technology features outstanding properties of use and enables the manufacture of surfaces, which meet the quality requirements regarding chemical and mechanical resistance (Garrat, 1996). The photoinitiator is an essential ingredient of UV-curable systems and has to fulfill a number of requirements like nonyellowing, low odor and high reactivity (Dietliker, 1991; Fouassier, 1995). However, fragmentation processes of photoinitiators form a number of reaction products, which may contribute to indoor air pollution. Benzaldehyde and alkyl-substituted benzaldehydes are usual components, because derivatives of acetophenone are frequently applied and V-cleavage (Norrish-l) is the most important reaction path (Saithammer, 1999a; Salthammer et al., 1999a). As a consequence, new photoinitiators of high reactivity but low volatility have been developed (Köhler, 1997; Hofmockel, 1999). In most UV-cured lacquer systems, a wide variety of acrylate binders and reactive diluents are used for controlling physical properties like viscosity, because usual binders are often not suitable for certain applications. Acrylates are classified as mono-, bi- and polyfunctional, according to the number of terminal - groups (Garrat, 1996). The monomers are irritant and require certain safety precautions for handling. This problem can be overcome by using more modern binders like low viscous polyether or polyester acrylates (BASF, 1999).
The release of VOC from UV-cured surfaces has been studied by several authors (Fischer and Böhm, 1994; Jann et al., 1997; EPA, 1998; Salthammer, 1997). It could be demonstrated, that the emission behavior is extremely sensitive to the conditions of the manufacturing process (Salthammer, 1996). Therefore, uncontrolled reactions of remaining photoinitiator residues must be expected during use and for minimization of VOC emissions the following questions occur regarding the environmental properties of UV-cured furniture coatings in interiors:
o Which photoinitiators and photofragments emit from the surface of UV-cured furniture coatings?
o How high are the indoor air concentrations under dwelling conditions?
o How have the substances to be estimated regarding odor formation and toxicity?
o What is the influence of the radiation intensity on the emissions?
o How can the UV-systems be improved?
To obtain more detailed information on the emission characteristics of UV-cured systems, the release of VOC was studied in test chambers under controlled conditions. The resulting data are of high value for the optimization of formulations.
