Thermogravimetric Evaluation of Fungal Degradation of Wood

Authors

  • F. C. Beall
  • W. Merrill
  • R. C. Baldwin
  • J-H. Wang

Keywords:

Thermal analysis, isothermal TG, dynamic TG, <i>Betula alleghaniensis</i>, white rot, brown rot, <i>Polyporus versicolor</i>, <i>Poria monticola</i>, biodegradation, decay

Abstract

Yellow birch (Betula alleghaniensis Brit.) was degraded by a white rot fungus (Polyporus versicolor L. ex Fr.; now Coriolus versicolor (L.) Quél.) and a brown rot fungus (Poria monticola Murr.; now Poria placenta (Fr.) Cke.) under controlled conditions. Samples of known weight loss from fungi were milled to pass a 40-mesh screen, oven-dried, and then measured for rate of mass loss over selected temperature ranges. Rates of mass loss of nominal 4-mg samples were obtained isothermally in flowing oxygen using a thermo-gravimetric (TG) system containing a Cahn electrobalance. Activation energy (E) was found using zero-order kinetics for the initial mass loss. White-rotted birch (to 60% weight loss) had an E of 35 to 43 kcal/mole over the range of approximately 190 to 210 C. On the basis of TG data, the weight loss from fungal attack could be predicted within about 5%. Brown-rotted birch had more variation in E (30 to 44 kcal/mole), over a temperature range of 170 to 195 C. The rate of mass loss of brown-rotted birch (to 52% weight loss) was more sensitive to temperature because of the known nonlinear decrease in cellulose DP during fungal attack. Dynamic thermogravimetry, a much simpler method, indicated a similar degree of instability from fungal attack as did the isothermal tests. TG appears to be a viable research method to evaluate fungal attack of wood.

References

Beall, F. C. 1968. Thermal degradation analysis of wood and wood components. Ph.D. thesis, SUNY Coll. of For., Syracuse, N.Y. 240 pp.nCowling, E. B. 1961. Comparative biochemistry of the decay of sweetgum sapwood by white-rot and brown-rot fungi. USDA Tech. Bull. No. 1258. 79 pp.nFlynn, J. H., and L. A. Wall. 1966. General treatment of the thermography of polymers. J. Res. NBS70 A (6): 487-523.nSmith, R. S. 1975. Respiration methods to follow wood decay and evaluate toximetric potential of wood preservatives. Mat. Organ.10(4): 241-253.nTimell, T. E. 1965. Wood and bark polysaccharides. Pages 127-156 in W. A. Côté, ed. Cellular ultrastructure of woody plants. Syracuse Univ. Press, Syracuse, N.Y.n

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Published

2007-06-05

Issue

Number 3 / Fall 1976

Section

Research Contributions

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