Abstract
The effect of weathering on Scots pine (Pinus sylvestris) and Norway spurce (Picea abies) treated with unpigmented commercial primers was studied. Structural changes occurring in radial longitudinal surfaces during weathering over a period of 24 weeks were examined using a reflected light microscope and a scanning electron microscope. Micro-checks were aligned parallel to microfibrils of the cell wall or parallel to the axis of the tracheids, and occurred first in latewood. The first larger checks appeared in thin-walled earlywood tracheids near thick-walled latewood tracheids. After 12 weeks exposure, delamination of the secondary wall occurred. After 24 weeks there were some visible macroiscopic checks on the surfaces and very little separation of individual cells occurred. There were no notable differences in checking and surface erosion between pine and spruce. Blue stain colonization was found first in the cracks between tracheids and it was more common on pine than on spruce. The priming of wood did not prevent but retarded structural changes occurring in the underlying wood. The higher the level of the solid contents in the primers, the more likely the occurrence of structural changes was retarded.
Resume
On a étudié l'influence du vieillissement sur le pin sylvestre et l'épicéa recouverts d'impressions du commerce non pigmentées. Les changements structuraux se produisant sur les faces longitudinales radiales pendant un vieillissement naturel de 24 semaines ont été examinés au microscope à lumière réfléchie et au microscope électronique à balayage.
De petites fissures alignées parallèlement aux microfibrilles de la paroi cellulaire ou à l'axe des trachéides se produisent d'abord dans le bois final. Les premières fissures plus larges apparaissent dans les trachéides à parois fines du bois initial à proximité des trachéides à parois épaisses du bois final. Après 12 semaines d'exposition, une délamination de la parois secondaire apparaît. Après 24 semaines, apparaissent des fissures macroscopiques en surface et une légère séparation des cellules. Une colonisation par des champignons de bleuissement est observée d'abord dans les fissures inter-trachéides aux endroits où les parois des trachéides commencent à se dissocier les unes des autres. L'intensité du bleuissement dépend de l'incorporation de fongicide dans l'impression étudiée.
Le revêtement du bois par l'impression n'empêche pas les modifications de la structure mais il les retarde. Plus le contenu de l'impression est riche en extraits secs, plus il est vraisemblable que les changements dans la structure du bois soient retardés. Les impressions appliquées ont subi une érosion superficielle pendant l'exposition. Aucune différence notable n'est à signaler entre le pin sylvestre et l'épicéa en ce qui concerne les fissurations et l'érosion mais le bleuissement s'est développé de manière plus importante dans le pin.
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References
Feist, W. C. and Hon, D. N.-S., ‘Chemistry of weathering and protection’, in ‘Chemistry of Solid Wood’, edited by R. M. Rowell, Advances in Chemistry Series 207 (ACS, Washington, DC, 1984) pp. 401–451.
Ashton, H. E., ‘Clear finishes for exterior wood: field exposure tests’,J. Paint Technol. 39(507) (1967) 212–224.
Williams, R. S., Winandy, J. E. and Feist, W. C., ‘Paint adhesion to weathered wood’,J. Coatings Technol. 59(749) (1987) 43–49.
Williams, R. S., Plantinga, P. L. and Feist, W. C., ‘Photodegradation of wood affects paint adhesion’,Forest Products J.40(1) (1990) 45–49.
Miniutti, V. P., ‘Microscale changes in cell structure at softwood during weathering’,Forest Products J. 14 (1964) 571–576.
Futo, L. P., ‘Der photochemische Abbau des Holzes als Präparations-und Analysenmethode’,Holz Roh-und Werkstoff 32(8) (1974) 303–311.
Chang, S.-T., Hon, D. N-S. and Feist, W. C., ‘Photodegradation and photoprotection of wood surfaces’,Wood and Fiber 14(2) (1982) 104–117.
Kuo, M. L. and Hu, N., ‘Ultrastructural changes of photodegradation of wood surfaces exposed to UV’,Holzforschung 45(5) (1991) 347–353.
Groves, K. W. and Banana A. Y., ‘Weathering characteristics of Australian grown Radiata pine’,J. Inst. Wood Sci. 10(5) (1985) 210–213.
Evans, P. D., ‘Structural changes inPinus radiata during weathering’,J. Inst. Wood Sci. 11 (5) (1989) 172–181.
Feist, W. C., ‘Weathering and protection of wood’ in Proceedings of 79th Annual Meeting of the American Wood-preservers' Association, Kansas City, April 1983 (AWPA, Stevensville, MD, 1983) pp. 195–205.
Suomi-Lindberg, L., Ahola, P. and Paajanen, L., ‘Water repellency of unpigmented trade sales primers’,Färgoch lack Scand.37 (11) (1991) 241–244.
Schneider, M. H., ‘Scanning electron microscope of a coating component deposited from solution into wood’,J. Oil Colour Chem. Assoc. 62 (11) (1979) 441–444.
Evans, P. D. and Banks, W. B., ‘Degradation of wood surfaces by water’,Holz Roh-und Werkstoff 48(4) (1990) 159–163.
Bravery, A. F. and Miller, E. R., ‘The role of pretreatment in the finishing of exterior softwood’, in Proceedings of the Annual Convention of the British Wood Preserving Association, Cambridge, June 1980, (BWPA, London, 1980) pp. 14–22.
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Paajanen, L.M. Structural changes in primed Scots pine and Norway spruce during weathering. Materials and Structures 27, 237–244 (1994). https://doi.org/10.1007/BF02473038
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DOI: https://doi.org/10.1007/BF02473038