Effect of species type and sanding sequence on the adhesion strength and the interphase region of Polyurethane coating and veneer

Document Type : Research Paper

Authors

1 Assistant Professor, Department of Wood Technology and Engineering, Faculty of Wood and Paper Engineering, University of Agricultural Sciences and Natural Resources, Gorgan, Iran.

2 M.Sc. graduated, Wood-Based Composites, Wood Technology and Engineering Department, University of Agricultural Sciences and Natural Resources, Gorgan. Iran.

3 Associate professor, Wood Technology and Engineering Department, Faculty of Wood and Paper Engineering, University of Agricultural Sciences and Natural Resources, Gorgan. Iran

4 1. Assistant professor, Wood Technology and Engineering Department, Faculty of Wood and Paper Engineering, University of Agricultural Sciences and Natural Resources, Gorgan. Iran

Abstract

The purpose of this research was the investigation of sanding sequence and coating thickness effect on adhesion strength of coating in two species: beech and elm. For this purpose, beech and elm veneers with 0.6 mm thickness were laminated on MDF with 16 mm thickness by UF and hot press. The surface of the laminated panels was sanded by two different sequences; the soft (180-280 grits) and rough (150-180 grits) one. Before the coating application, the surface was sanded with 400 grits. Then they were coated with polyurethane in two forms of one and two-layered coating. After that, the adhesion strength test was done on specimens according to ASTM D4541. To have a more precise investigation of the interphase region of coating-veneer, photomicrographs were captured by fluorescent microscopy to analyze and calculate the effective penetration parameter of the coating into the wood texture. The results showed that two species respond to sanding sequences differently and a thicker coating layer increased the adhesion strength. Beech as a diffuse-porous wood had the finer texture and higher density compared with elm. Therefore, the adhesion strength of the beech veneer was declined by 13.8 % and reaches 2.59 MPa due to the use of a rough sanding sequence. However, these sequences caused the opposite result in elm veneer and led to a 25.7 % adhesion improvement (3.23 MPa). The study on microphotographs and the effective penetration parameter stated that an even thickness of the coating layer and effective penetration reduction has been possible when the rough sequence and soft one are applied on elm and beech, respectively.

Keywords

Main Subjects

References

[1]   Talaei, A., Salehzadeh, M., and Abdolzadeh, H. 2016. Study on adhesion strength of clear coatings in beech -furfuryl alcohol wood polymer. Iranian Journal of Wood and Paper Industries, 7(1), 115–127.
[2]   Ghofrani, M., and Khojasteh Khosro, S. 2014. The effect of wood surface finishing quality on the adhesion strength of clear coat. Journal of Color Science and Technology, 7, 339–345.
[3]   Ghofrani, M., Manavi, G., and Mirshokraei, S. A. 2014. Investigation on the Scratch Strength of Clear Paints Used in Furniture Industries on the Wood Species Beech, Elm, Alder and Spruce. Iranian Journal of Wood and Paper Industries, 5(1), 33–44.
[4]   Kassiriha, S. M., Soltani, R., and Panahi, Y. 2010. polyurethane resins properties and application. Iranian Corrosion Association.
[5]   Vitosyte, J., Ukvalbergieno, K., and Keturakis, G. 2012. The effects of surface roughness on adhesion strength of coated ash (Fraxinus excelsior L.) and Birch (Betula L.) wood. Journal of Materials Sciences (Medziagotyra), 18(4), 347–351.
[6]   Ghofrani, M., Samadi, E., and Khojasteh Khosro, S. 2016. Heat treatment of wood and the investigation of its effect on surface wettability and adhesion strength of coating. Iranian Journal of Wood and Paper Science Research, 31(2), 362–373.
[7]   Gholamiyan, H., Tarmian, A., and Abdulkhani, A. 2017. Improvement of adhesion strength of polyurethane and alkyd coatings using sol-gel method nano-silane wood surface modification H. Iranian Journal of Wood and Paper Science Research, 32(3), 322–333.
[8]   De Meijer, M. 2004. A review of interfacial aspects in wood coatings: wetting, surface energy, substrate penetration and adhesion. COST E18, High Performance Wood Coating. Final seminar, (January 2005), 1–16.
[9]   Ozdemir, T., and Hiziroglu, S. 2009. Influence of surface roughness and species on bond strength between the wood and the finish. Forest Products Journal, 59(6), 90–94.
[10] Ugulino, B., and Hernández, R. E. 2018. Analysis of sanding parameters on surface properties and coating performance of red oak wood. Journal of Wood Material Science and Engineering, 13(2), 64–72.
[11] Hosseinifard, M. S., Khojasteh Khosro, S., and Mohebby, B. 2015. Evaluate the effect of oil-heat treatment of Fir species on contact angle and adhesion strength of water based clear and acid catalyzed transparent coat. Iranian Journal of Wood and Paper Science Research, 30(1), 173–181.
[12] Manavi, G., Ghofrani, M., and Mirshokraei, S. A. 2012. Effects of wood type, moisture content and paint type on adhesion strength of conventional clear paints used in furniture manufacture. Iranian Journal of Wood and Paper Science Research, 27(4), 743–753.
[13] Ghofrani, M., Mohammad Moradi, Z., and Khojasteh Khosro, S. 2016. Investigation on the effect of different methods of applying transparent coatings on adhesion strength of coating in wooden surfaces. Iranian Journal of Wood and Paper Science Research, 31(2), 248–260.
[14] ASTM D4541, 2002, Standard Test Method for Pull- Off Strength of Coatings Using Portable Adhesion Testers, Annual Book of ASTM Standard. (2002).
[15] Bastani, A., Adamopoulos, S., and Militz, H. 2015. Gross adhesive penetration in furfurylated, N-methylol melamine-modified and heat-treated wood examined by fluorescence microscopy. European Journal of Wood and Wood Products, 73(5), 635–642.
[16] Latibari, A. J. 2007. Science and Technology of Adhesion for Liqnocellulosic Substances. Islamic Azad University, Karaj Branch.
Iranian Journal of Wood and Paper Industries
Volume 11, Issue 2
September 2020
Pages 317-332

Files

Share

How to cite

Statistics