Photodegradation and Photoprotection of Wood Surfaces

Authors

  • Shang-Tzen Chang
  • David N.-S. Hon
  • William C. Feist

Keywords:

Scanning electron microscope (SEM), chromic acid, ferric chloride, ultraviolet light, southern yellow pine

Abstract

Photodegradation of southern yellow pine and its protection have been studied. Scanning electron micrographs showed that most of the cell walls on exposed transverse surfaces were separated at the middle lamella region after only 500 h of ultraviolet light irradiation. Fibers at the surface were degraded severely after 1,000 h of irradiation. Half-bordered pits and bordered pits on exposed radial surfaces were severely damaged by ultraviolet light. Enlargement of pit apertures as well as loss of pit domes was observed. However, wood irradiated on tangential surfaces was quite resistant to UV irradiation; only microchecks were observed. The photodegradative effect on wood surfaces can be mitigated by treating with aqueous solutions of chromic acid or ferric chloride. Only relatively small amounts of these chemicals are needed for effective protection. Possible chemistry and mechanisms of degradation and protection are discussed.

References

Black, J. M., and E. A. Mraz. 1974. Inorganic surface treatments for weather-resistant natural finishes. USDA For. Serv. Res. Pap. FPL-232.nBrowne, F. L. 1960. Wood siding left to weather naturally. S. Lumberman 141-143.nFeist, W. C. 1978. Protecting wooden structures. Chemtech.8(3):160-162.nFeist, W. C. 1979. Protection of wood surfaces with chromium trioxide. USDA For. Serv. Res. Pap. FPL-339, For. Prod. Lab. Madison, WI.nGellerstedt, G., and E. L. Petterson. 1977. Light-induced oxidation of lignin. Part 2. The oxidative degradation of aromatic rings. Sven. Papperstidn.80:15-21.nHon, D. N.-S. 1981a. Photochemical degradation of lignocellulosic materials. Pages 229-281 in N. Grassie, ed. Developments in polymer degradation. Chapter 8. Appl. Sci. Publ., London.nHon, D. N.-S. 1981b. Yellowing of modern papers. In J. L. Williams, ed. Preservation of paper and textiles of historic and artistic value. Am. Chem. Soc., Washington, DC (in press).nHon, D. N.-S., and W. C. Feist. 1980a. Role of free radicals in weathering of wood. Paper presented at the 34th Annual Meeting, For. Prod. Res. Soc., Boston, MA. July 6-10.nHon, D. N.-S., and W. C. Feist. 1980b. Weathering reactions of wood surfaces. Paper presented at the 2nd Chemical Congress of the North American Continent, Las Vegas, NE, August 24-29.nHon, D. N.-S., and G. Ifju. 1978. Measuring penetration of light into wood by detection of photo-induced free radicals. Wood Sci.11:118-127.nHon, D. N.-S., G. Ifju. and W. C. Feist. 1980. Characteristics of free radicals in wood. Wood Fiber12(2):121-130.nHon, N.-S. 1975a. Formation of free radicals in photoirradiated cellulose. IV. Effect of ferric ions. J. Appl. Polym. Sci.19:2789-2797.nHon, N.-S. 1975b. Formation of free radicals in photoirradiated cellulose. VI. Effect of lignin. J. Polym. Sci. Polym. Chem. Ed.13:2641-2652.nKalnins, M. A. 1966. Surface characteristics of wood as they affect the durability of finishes. Part II. Photochemical degradation of wood. USDA For. Serv. Res. Pap. FPL-57. For. Prod. Lab., Madison, WI.nKringstad, K. P., and S. Y. Lin. 1970. Mechanism in the yellowing of high-yield pulp by light. Structure and reactivity of free radical intermediates in the photodegradation of lignin. Tappi53:2296-2301.nLeary, G. J. 1967. The yellowing of wood by light. Tappi50:17-19.nLeary, G. J. 1968. The yellowing of wood by light. Part II. Tappi51:257-260.nLin, S. Y., and J. Gierer. 1972. Photodegradation of lignin. A contribution to the mechanism of chromophore formation. Sven. Papperstidn.75:233-239.nLuner, P. 1960. Brightness of high-yield pulps. II. Reductive bleaching of cold soda pulp from white birch with sodium borohydride. Tappi43:819-826.nMiniutti, V. P. 1964. Microscale change in cell structure of softwood surfaces during weathering. For. Prod. J.14:571-576.nMiniutti, V. P. 1967. Microscopic observations of ultraviolet irradiation and weathered softwood surfaces and clear coatings. USDA For. Serv. Res. Pap. FPL-74.nYusoff, M. M., and D. N.-S. Hon. 1980. Photoprotection of thermomechanical pulp fibers. Unpublished results.n

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Published

2007-06-27

Issue

Number 2 / April 1982

Section

Research Contributions

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