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Technical Note: Wettability of Hydrothermally-Treated Hardwood Surfaces in PMDI Adhesive at Elevated Temperatures

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Applied Engineering in Agriculture. 29(2): 281-285. (doi: 10.13031/2013.42650) @2013
Authors:   T. Eric McConnell, Sheldon Q. Shi
Keywords:   Dynamic Contact Angle (DCA); Hardwood; Hydrothermal treatment; pMDI adhesive; Wood.

Abstract. Hydrothermally treating the wood obtained from hardwood trees at relatively mild temperatures could add value to lignocellulosic ethanol conversion by providing a raw material for manufacturing wood composite products. The objective of this experiment was to determine the effect of increased ambient adhesive temperatures, more representative of the manufacturing process, on the dynamic contact angle (DCA) of red oak, sweetgum, and yellow-poplar wood hydrothermally treated at 175°C for 30 min. The DCAs were obtained via the Wilhelmy plate technique. Polymeric diphenylmethane diisocyanate resin was investigated at three temperatures: 20°C, 50°C, and 80°C. The species and adhesive temperature independently and significantly affected the DCA. Wood wetting increased as the adhesive temperature increased. The temperature main effect was nonlinear, with the high ambient temperature producing the least contact angle. Yellow-poplar’s DCA was significantly lower than the other species. An improved network of interpenetration may be possible using modified hardwoods, although potential issues with over-penetration of the adhesive should be monitored during the manufacturing process.

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