Evaluation Of Varnish Coating Performance For Two Surfacing Methods On Sugar Maple Wood

Authors

  • Luiz Fernando de Moura
  • Roger E. Hernández

Keywords:

Planing, sanding, wetting properties, roughness, varnishing, sugar maple

Abstract

The understanding of adhesion mechanisms on wood surfaces is essential in order to extend service life of film-forming coatings. Pull-off adhesion test and accelerated aging were used to assess adhesion and performance of a high-solids polyurethane coating on sugar maple wood. Two surfacing processes were employed prior to coating: peripheral knife planing and sanding. Planing produced surfaces and subsurfaces virtually free of damage, which provoked a higher coating penetration. However, this was not sufficient to promote good adhesion. Sanding offered better wetting properties of wood surface even though superficial crushing of cells hindered coating penetration. Wetting was facilitated in the direction of abrasive scratches. Stronger pull-off adhesion and better aging-resistance of films on sanded surfaces were mainly associated to the presence of torn-out micro-fibrils, which promoted a better mechanical anchorage and offered a greater actual surface available to coating and wood interactions. Surface roughness, wetting properties and film aging-resistance were significantly correlated with pull-off adhesion.

References

American Society for Testing and Materials (ASTM). 1995. Standard test method for pull-off strength of coatings using portable adhesion testers. ASTM D 4541. Philadelphia, PA.nBackman, A. C., and K. A. H. Lindberg. 2002. Interaction between wood and polyurethane-alkyd lacquer resulting in a decrease in the glass transition temperature. J. Appl. Polym. Sci. 85:595-605.nCantin, M. 1967. Propriétés d'usinage de 16 essences de bois de l'Est du Canada. Direction générale des Forêts. Publication n° 1111 S. 31 pp.nCollett, B.M. 1972. A review of surface and interfacial adhesion in wood science and related fields. Wood Sci. Technol. (6):1-42.nDe Meijer, M., K. Thurich, and H. Militz. 1998. Comparative study on penetration characteristics of modern wood coatings. Wood Sci. Technol. 32(5):347-365.nDolenko, A. J., R. L. Desai, and M. R. Clarke. 1974. Application parameters for water-based coatings on wood products. J. Inst. Wood Sci. 6(5):18-22.nGarrett, H.E. 1964. Contact angles and their significance for adhesion. Page 19 in Proc. Conferences of the Northampton College of Advanced Technology, EC1, England.nGray, V. R. 1964. Contact angles, surface tensions and adhesion. Page 42 in Proc. Conferences of the Northampton College of Advanced Technology, EC1, England.nGray, V. R. 1965. Adhesives in the timber trades. Page 71 in Proc. Conferences of the Northampton College of Advanced Technology, EC1, England.nHernández, R. E., and L. F. de Moura. 2002. Effects of knife jointing and wear on the planed surface quality of northern red oak wood. Wood Fiber Sci. 34(4):540-552.nInternational Organization for Standardization (ISO). 1984. Rugosité de surface—Terminologie—Partie 1: Surface et ses paramètres. ISO 4287-1. Geneva, It.nJokerst, R. W., and H. A. Stewart. 1976. Knife- versus abrasive-planed wood: Quality of adhesive bonds. Wood Fiber 8(2):107-113.nKwok, D. Y., and A. W. Neumann. 2000. Contact angle measurements and contact angle interpretation: relevance to the thermodynamics of adhesion. In Acid-base interactions: relevance to adhesion science and technology, vol II. Utrecht, Holland. Pp. 91-166.nLewis, A. F., and L. J. Forrestal. 1969. Adhesion of coatings. In Treatise on Coatings, vol II. Characterization of Coatings: Physical Techniques. Marcel Dekker, New York. Pp. 57-98.nPodgorski, L., B. Chevet, L. Onic, and A. Merlin. 2000. Modification of wood wettability by plasma and corona treatments. Int. J. Adhes. Adhes. 20(2):103-111.nRichter, K., W. C. Feist, and M. T. Knaebe. 1995. The effect of surface roughness on the performance of finishes. Part 1. Roughness characterization and stain performance. Forest Prod. J. 45(7/8):91-97.nShi, S. Q., and D. J. Gardner. 2001. Dynamic adhesive wettability of wood. Wood Fiber Sci. 33(1):58-68.nStewart, H. A., and J. B. Crist. 1982. SEM examination of subsurface damage of wood after abrasive and knife planing. Wood Sci. 14(3):106-109.nVasishth, R. C., F. R. Giltrow, and Z. Koran. 1974. SEM studies of weathered varnish on wood. Wood Sci. 6(3):278-284.nWålinder, M. 2000. Wetting phenomena on wood. Factors influencing measurements of wood wettability. In KTH-Royal Institute of Technology, Department of Manufacturing Systems, Wood Technology and Processing, Stockholm, Sweden. 61 pp.nWenzel, R. N. 1936. Resistance of solid surfaces to wetting by water. Ind. Eng. Chem. 28(8):988-994.nWilliams, R. S., and W. C. Feist. 1994. Effect of preweathering, surface roughness, and wood species on the performance of paint and stains. J. Coating Technol. 66(828):109-121.nWu, S. 1982. Polymer interface and adhesion. Marcel Dekker, New York, NY. 630 pp.nWulf, M., P. Netuschil, G. Hora, P. Schmich, and H. K. Cammenga. 1997. Investigation of the wetting characteristics of medium density fibreboards (MDF) by means of contact angle measurements. Holz Roh-Werkst. 55: 331-335.nYalinkiliç, M. K., R. Ilhan, Y. Imamura, M. Takahashi, Z. Demirci, A.C. Yalinkiliç and H. Peker. 1999. Weathering durability of CCB-impregnated wood for clear varnish coatings. J. Wood Sci. 45(6):502-514.n

Downloads

Published

2007-06-05

Issue

Number 2 / April 2005

Section

Research Contributions

License

The copyright of an article published in Wood and Fiber Science is transferred to the Society of Wood Science and Technology (for U. S. Government employees: to the extent transferable), effective if and when the article is accepted for publication. This transfer grants the Society of Wood Science and Technology permission to republish all or any part of the article in any form, e.g., reprints for sale, microfiche, proceedings, etc. However, the authors reserve the following as set forth in the Copyright Law:

1. All proprietary rights other than copyright, such as patent rights.

2. The right to grant or refuse permission to third parties to republish all or part of the article or translations thereof. In the case of whole articles, such third parties must obtain Society of Wood Science and Technology written permission as well. However, the Society may grant rights with respect to Journal issues as a whole.

3. The right to use all or part of this article in future works of their own, such as lectures, press releases, reviews, text books, or reprint books.