Characterization of low molecular weight phenol formaldehyde diffusion into wood

Past research has suggested the use of bulking agents to improve the dimensional stability of wood products; however, little has been done with regard to the fundamental understanding of mass transfer during the bulking process. This research addresses the dearth of information in this area by studying the mechanism of diffusion of low molecular weight phenol formaldehyde, impregnated phenol formaldehyde (IPF), a water insoluble or non-leachable bulking agent, into wood.; An unsteady state diffusion experiment was carried out to: (a) verify the possibility of Fickean diffusion and (b) evaluate the concentration profiles of the radial diffusion of IPF into wood.; Aspen (Populus tremuloides Michx.) and red pine (Pinus resinosa Ait.) water saturated wooden blocks were immersed in IPF for varying times. Cross-sections were taken from both ends of the treated samples and heat treated to cure the IPF. Depth of radial and tangential penetration of IPF into defect free aspen and red pine were measured by image analysis. Subsequently, concentration profiles of the radial diffusion of IPF were determined from the remaining portion of the sample. Specimens were thin sectioned with a sliding microtome and the sections were first weighed on a microbalance to determine their moisture content and then solvent extracted with methanol to determine the weight of diffused IPF within each thin section. The methanol solvent was evaporated and the remaining cured IPF weighed using a microbalance and the concentration profiles determined. A microtechnique was implemented to determine the IPF concentration profile.; Results from the depth of radial and tangential penetration into aspen and red pine, respectively, showed evidence of Fickean diffusion. The presence of spiral grain and specific gravity variation effected the relationship between the immersion time and the depth of penetration.; IPF concentration profiles showed that the implemented microtechnique provided a more thorough concentration profile than those previously reported. The radial concentration profile of IPF into aspen for different immersion times describes reasonably well the IPF diffusion process. The profiles also show, based on the microgravimetric technique, the influence of wood anatomical features and specific gravity variations on diffusion.