Chemical and mechanical changes during photooxidation of an acrylic clear wood coat and its prevention using UV absorber and micronized TiO2

Published Date

July 2013, Vol.98(7):1329–1338, doi:10.1016/j.polymdegradstab.2013.03.029

Title 

Chemical and mechanical changes during photooxidation of an acrylic clear wood coat and its prevention using UV absorber and micronized TiO₂

• Author 

• Boris Forsthuber ^a,,
• Ulrich Müller ^b
• Alfred Teischinger ^c
• Gerhard Grüll ^a

• aHolzforschung Austria, Franz-Grill-Strasse 7, 1030 Vienna, Austria
• bWood K plus – Competence Centre for Wood Composites and Wood Chemistry, St.-Peter-Strasse 25, 4021 Linz, Austria
• cDept. Of Wood Science and Technology, University of Natural Resources and Life Sciences, Gregor Mendel Strasse 33, 1180 Vienna, Austria

Received 20 November 2012. Revised 27 March 2013. Accepted 31 March 2013. Available online 17 April 2013.

Abstract

In this study, we hypothesized that the use of UV absorber of the hydroxy-benzotriazole class (BTZ) and micronized TiO₂ (NTiO₂) as mineral UV screener could stabilize the chemical and mechanical properties of clear wood coatings based on a high T_g/low T_g multiphase acrylic binder dispersion. The photooxidation rates were compared using ATR-FTIR techniques and tension tests. For qualitative and quantitative chemical analysis and correlation to the mechanical properties, multiple linear regression (MLR) was used, which was a suitable method to monitor the chemical changes of the polymeric binder and to investigate the influence of these light stabilizing additives on the photooxidation behavior. The analysis of mechanical properties of the acrylic binder during exposure to Xenon arc light showed that both BTZ and NTiO₂ stabilized the Young's Modulus and the elongation at break during the whole cycle. BTZ showed better results. However, it led to a strong decrease of the initial Young's Modulus whereas NTiO₂ showed no comparable effect. We concluded that BTZ was very efficient in reducing the photooxidation and the accompanied change of the elastic properties of the acrylic binder. NTiO₂ only stabilized the high T_gcomponent of the multiphase acrylic binder whereas the photooxidation of the low T_gcomponent was accelerated. This may be explained by a photocatalytical activity of NTiO₂.

Keywords

Wood coatings

Clear coatings

UV absorber

UV screener

(Meth)acrylates

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