Effects of Moisture on the Chemical Modification of Wood With Epoxides and Isocyanates


  • Roger M. Rowell
  • W. Dale Ellis


Chemical modification, moisture content, epoxides, isocyanates, ponderosa pine


The effects of moisture on the reaction of epoxides and isocyanates with wood were investigated. Ponderosa pine at 0%, 5%, and 10% equilibrium moisture contents was reacted separately with either propylene oxide or butylene oxide catalyzed with triethylamine, or with butyl isocyanate catalyzed with dimethylformamide. Five successive treatments were performed while recycling the treatment solutions on specimens with 5% and 10% equilibrium moisture contents. Grinding and extracting the treated wood showed significant losses of nonbonded chemical at these original moisture levels. When antishrink efficiency was determined on propylene oxide treated wood using the double water-soak method, a high resistance to dimensional changes was observed on the first water-soak cycle. Most of this dimensional stability was lost based on the second water-soak cycle, showing that nonbonded polymer had been extracted. Somewhat higher antishrink efficiency values were obtained for butylene oxide and butyl isocyanate treatments. Gas chromatographic determination of products from the propylene and butylene oxide/triethylamine treating solutions showed little water buildup. Total accountable volatile products decreased with successive treatments on specimens originally containing 5% and 10% moisture, indicating the formation of nonvolatile polyglycols in the wood cell wall. Determination of butyl isocyanate solutions following each treatment showed that one quarter or less of the active isocyanate was lost due to reaction with the water in the wood.


American Society for Testing and Materials. 1970. Isocyanate groups in urethane materials or prepolymers. ASTM D 2572. ASTM, Philadelphia, PA.nJohnson, B. R., and D. I. Gutzmer. 1981. Marine exposure of preservative-treated small wood panels. U.S. Department of Agriculture, For. Serv. Res. Pap. FPL 399. For. Prod. Lab., Madison, WI. 14 pp.nRowell, R. M. 1980. Distribution of reacted chemicals in southern pine modified with methyl isocyanate. Wood Sci.13(2):102-110.nRowell, R. M., and W. D. Ellis. 1978. Determination of dimensional stabilization of wood using the water-soak method. Wood Fiber10(2):104-111.nRowell, R. M., and W. D. Ellis. 1979. Chemical modification of wood: Reaction of methyl isocyanate with southern pine. Wood Sci.12(1):52-58.nRowell, R. M., and W. D. Ellis. 1981. Bonding of isocyanates to wood. Pages 263-284 in K. N. Edwards, ed. Urethane chemistry and applications. Am. Chem. Soc. Symposium Series172, Chap. 19.nRowell, R. M., and D. I. Gutzmer. 1975. Chemical modification of wood: Reactions of alkylene oxides with southern yellow pine. Wood Sci.7(3):240-246.nRowell, R. M., D. I. Gutzmer., I. B. Sachs, and R. E. Kinney. 1976. Effects of alkylene-oxide treatments on dimensional stability of wood. Wood Sci.9(1):51-54.nRowell, R. M., S. V. Hart, and G. R. Esenther. 1979. Resistance of alkylene-oxide modified southern pine to attack by subterranean termites. Wood Sci.11(4):271-274.n






Research Contributions