The Adhesion of an Acrylic Primer to Weathered Radiata Pine Surfaces


  • Phan D. Thay
  • Philip D. Evans


<i>Pinus radiata</i>, weathering, acrylic primer, adhesion, earlywood, latewood, SEM


Radiata pine (P. radiata) heartwood and sapwood were cut to produce flat-grain blocks in which the upper tangential surface consisted of either earlywood or latewood. Blocks were subjected to 6 weeks of weathering during an Australian summer and coated with an acrylic primer; and the adhesion of the primer to the different weathered and unweathered wood surfaces was assessed using a tape test. Primer adhesion decreased on earlywood as a result of weathering, but increased on latewood. Scanning electron microscopy (SEM) observations of wood/primer interfaces after tape testing suggested that the increase in primer adhesion on weathered latewood was due to greater penetration of the primer into relatively undegraded subsurface tracheids. There was little difference in the adhesion of the primer to heartwood or sapwood, but, as expected for unweathered surfaces, primer adhesion was greater on earlywood than on latewood. The practical implications of these findings for the coating of exterior wood are discussed briefly.


Ashton, H. E. 1967. Clear finishes for exterior wood field exposure tests. J. Paint Technol. 39(507):212-224.nASTM. 1976. Standard methods for measuring adhesion by tape test. American National Standard D3359, 661-664, American Society for Testing & Materials, Philadelphia, PA.nBoxall, J. 1977. Painting weathered timber. Buildg. Res. Est. (UK) Information Sheet. 20/77:1-2.nBrowne, F. L. 1931. Adhesion in the painting and in the gluing of wood. Ind. Eng. Chem. 23:290-294.nCech, M. Y., and D. R. Huffman. 1970. Dynamic transverse compression treatment of spruce to improve intake of preservatives. Forest Prod. J. 20:47-52.nDesai, R. L. 1967. Coating adhesion to weathered wood. Can. Dept. Fisheries and Forestry, Bi-monthly Res. Notes. 23:36-37.nDerbyshire, H., E. R. Miller, and H. Turkulin. 1996. Investigation into the photodegradation of wood using microtensile testing. Part 2: An investigation of the changes in tensile strength of different softwood species during natural weathering. Holz Roh-Werkst. 54:1-6.nEvans, P. D., P. D. Thay, and K. J. Schmalzl. 1996. Degradation of wood surfaces during natural weathering. Effects on lignin and cellulose and on the adhesion of acrylic latex primers. Wood Sci. Technol. 30:411-422.nJewell, G. W. 1993. Latex properties: Effect of water phase and particle size. Page 323 in Anon. Surface coatings raw materials and their usage. Univ. NSW Press, Sydney, Australia.nMiller, E. R. 1981. Chemical aspects of external coatings for softwoods. Pages 91-98 in Proc. Symp. Chem. Aspects of Wood Tech. Swed. For. Res. Lab. Sodergan, Stockholm, Sweden.nRudman, P. 1965. Fine structure of wood. Nature 208:55-56.nSiau, J. F. 1984. Transport processes in wood. Springer-Verlag, Berlin, Germany. 245 pp.nSingh, A., B. Dawson, M. Schwitzer, and M. Singh. 1996. The effects of ponding on wood-coating interaction. Pages 72-80 in Proc. 3rd Pac. Rim Bio-based Composites Symp. Kyoto, Japan.nStalker, I. N. 1971. A safer test for distinguishing heartwood and sapwood in pines. J. Inst. Wood Sci. 5:21-29.nUnderhaug, A., T. J. Lund, and K. Kleive. 1983. Wood protection—The interaction between substrate and product and the influence on durability. J. Oil & Col. Chem. Assoc. 66:345-350.nWilliams, R. S., and W. C. Feist. 1993. Durability of paint or solid-color stain applied to preweathered wood. Forest Prod. J. 43:8-14.nWilliams, R. S., J. E. Winandy, and W. C. Feist. 1987. Paint adhesion to weathered wood. J. Coat. Technol. 59(749):43-49.nWilliams, R. S., P. L. Plantinga, and W. C. Feist. 1990. Photodegradation of wood affects paint adhesion. Forest Prod. J. 4:45-49.n






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