No abstract

Rates of penetration of polyethylene glycol (PEG) molecular weight (MW) 1,000, 2,000, and 4,000 from 30% aqueous solutions into hydrated cell walls of red pine samples following vacuum impregnation were estimated by examining retained swelling of the samples after different post-treatment conditioning times. To model PEG diffusion into wood cell walls, a hollow cylinder diffusion model was developed and diffusion coefficients were estimated and compared to those determined with a plane membrane diffusion model. The models gave similar results. The diffusion coefficient of PEG MW 1,000 at room temperature was estimated to be in the order of 10 -13 m 2 /s, while the penetration rates of both PEG 2,000 and 4,000 were about an order lower. These findings indicate that treatments of wood by PEG can be significantly shorter than present practices of soaking green samples in solution if the samples are vacuum/pressure impregnated with PEG solution.

This study used a capillary rheometer to determine the impact that shear and elongational flow have on the breakage of aspen fibers in a polypropylene matrix. Composites were processed at different concentrations, temperatures, and rates of strain. The influence of the processing parameters was also analyzed. The difference in breakage of the fibers was assessed through their weight–average fiber length. Results showed that both types of flow exert influence on the total breakage of the fibers. In some cases, the percentage of breakage in the elongational flow is higher. The level of fiber breakage was similar for all fiber concentrations and shear rates. Temperature influence depended on the type of flow.