Prevention of Photodegradation in Polyurethane and UV Curable Wood Coatings


Esen D. S., Ergüven E., Er D., Arsu N.

7th European Symposium of Photopolymer Science, İstanbul, Turkey, 19 - 22 September 2022, pp.78

  • Publication Type: Conference Paper / Summary Text
  • City: İstanbul
  • Country: Turkey
  • Page Numbers: pp.78
  • Yıldız Technical University Affiliated: Yes

Abstract

Paint / varnish systems are used in variety of applications in wood coating industry to provide protection of wooden surfaces and an aesthetic appearance. Polyurethane paints and UV curable paints are the most preferable systems in wood coating sector. The biggest advantages of polyurethane systems are very good chemical and abrasion resistance, fast drying and good adhesion properties. In addition, UV systems, in which drying is provided by a photochemical process, are used in many areas and have many advantages such as fast curing, low energy and small space requirements, very low VOC and minimal waste. [1]

Yellowing problem can be observed in both polyurethane and UV curable systems overtime due to external effects (especially sunlight). One of the most effective way to prevent yellowing problem is using light stabilizers such as; UV absorbers, HALS (Hindered amine light stabilizers) and antioxidants [2-4].

In this study, some commercial antioxidant materials were used as an alternative to a commercial stabilizer, which is highly preferred but with restrictions on its use, and their effectiveness was compared. These materials added to our commercial polyurethane and UV curable paints to reduce yellowing and the results were compared with standard formulas. UV-curable formulations containing epoxy acrylate are applied to glass panels with 120 µ wet film thickness and cured with mercury lamps with different exposure time. Alkyd-based polyurethane paints containing different light stabilizers were mixed with an isocyanate hardener 50% by weight and applied to 3 different glass panels at 120 µ wet film thickness and cured under laboratory conditions. After curing, the hardness, brightness, yellowing and color values of all the polymeric films obtained were compared to each other and standard formulas. In addition, some of the polymeric films were tested with Q-SUN aging test device and the obtained data were compared with standard formula and each other.

References

[1] Rajkumar Singh Rawata, Nidhi Chouhana, Meenu Talwara, Rajendra Kumar Diwanb, Ajay Kumar Tyagia (2019). “UV coatings for wooden surfaces”. Prog. in Org. Coat. 135:490-495.

[2] Béatrice George, Ed Suttie, André Merlin, Xavier Deglise (2005). “Photodegradation and photostabilisation of woodthe state of the art”. Polymer Degradation and Stability 88:268-274.

[3] Boris Forsthuber, Gerhard Grüll (2010) “The effects of HALS in the prevention of acrylic clear topcoats and wooden surfaces”. Polymer Degradation and Stability 95:746-755.

[4] Pai-Lung Chou, Hui-Ting Chang, Ting-Feng Yeh, Shang-Tzen Chang (2008) “ Characterizing the conservation effect of clear coatings on photodegradation of wood”. Bioresource Technology 99:1073-1079.

Keywords: UV curing, wood coatings, polyurethane, yellowing, light stabilizers