Influence of Juvenile Wood on Dimensional Stability and Tensile Properties of Flakeboard

The purpose of this study was to determine if juvenile wood adversely affects the linear expansion, water adsorption, and thickness swell of aligned flakeboard. Literature on juvenile wood properties and their effects on product performance was reviewed. Veneer and lumber cut from 35-year-old plantation-grown loblolly pine were segregated by age and used to manufacture plywood and flake-board. As expected, longitudinal linear expansion of the juvenile (0 to 12 years old) veneer was greater than that of mature (13+ years old) veneer. At several levels of humidity exposure, linear expansion of symmetrical cross-laminated plywood made from the juvenile veneer was greater than that of plywood made from mature veneer. Significant increases in the linear expansion of three-layer cross-oriented flakeboard were also attributed to juvenile wood. Differences in the linear expansion of single-layer directional aligned flakeboards made from juvenile wood and from mature wood were not statistically significant for the most part. Analysis did show that test results were affected by tree-to-tree variation in wood age and sample variations. Accurate predictions of dimensional stability in three-layer cross-aligned panels were made using tensile and linear expansion properties derived from the directional flakeboard

Flakeboard Thickness Swelling. Part I. Stress Relaxation in a Flakeboard Mat

The steam injection schedule best suited for dimensionally stabilizing a flake mat is one in which steam treatment is initiated before the press is closed and is continued at least until the mat attains target thickness. Experiments showed that resinless mats treated with 20 sec of steam at 600 kPa had maximum thickness swelling of 205% compared to 350% for resinless mats pressed in a conventional fashion. Reductions in thickness swelling were proportional to steam duration and pressure. Mats treated with 20 sec of steam at 1,950 kPa had only one-tenth the thickness swelling measured in conventionally pressed mats. We believe that reduction of thickness swelling is dependent on a number of factors, including plasticization of the wood, "lignin" flow, and molecular changes in the wood structure

Effects of Microstructural Heterogeneity in Cement Excelsior Board

Heterogeneity in the properties and arrangement of constituents can have an important effect on a composite's properties. This paper evaluates the effects of variability in wood strand dimensions, mechanical properties, and orientation on the engineering properties of cement excelsior board. The finite element method is used to analyze a heterogeneous three-dimensional microstructure of strands, predicting elastic and strength properties. Results suggest that variability in strand mechanical properties can significantly lower composite tensile and compressive strengths, while composite stiffness is not affected. The model also predicts that relatively modest alignment of strands can lead to significant increases in composite strength and stiffness in the direction of alignment

Density Range of Compression-Molded Polypropylene-Wood Composites

Wood and polypropylene fibers were mixed together in various proportions and compression-molded to boards of various specific gravities. The full theoretical specific gravity range could not be obtained even when the boards were cooled in the press. Voids surrounding the wood fibers possibly were due to the shrinkage of the wood fiber following pressing. Bending and tension properties were influenced more by the compression of the wood fibers than by the percentage of wood fiber addition

Flakeboard Thickness Swelling. Part II. Fundamental Response of Board Properties to Steam Injection Pressing

The results of this study showed that the same relative reductions in thickness swelling (TS) previously obtained with steam-injection-pressed (SIP) resinless mats are also obtained in boards bonded with 3% isocyanate resin. Reductions in thickness swelling were proportional to steam time and pressure. Thickness swelling of 40% measured in conventionally pressed boards following a vacuum-pressure-soak treatment was reduced to 25% in a board exposed to 20 sec of steam at 600 kPa and to 6% in a board exposed to 40 sec of steam at 1,900 kPa. We believe that the reductions in thickness swelling result from a combination of flake plasticization, "lignin flow," and chemical modification. Bending properties of the SIP boards were substantially lower than that of conventionally pressed boards, which we attribute in part to the very short press times and the relatively fast decompression used to manufacture the SIP boards. Bending properties of SIP boards also suffered from a reduction of the vertical density gradient. However, this characteristic is favorable to shear properties

United States Department of Agriculture

Four flake furnishes differing in either target length and width or in production methods were combined and degraded to establish 13 different furnish types. Samples from each furnish type were then examined using image analysis techniques. By ranking the data from smallest to largest, percentile values were obtained for long chord, width, area, and perimeter. Cumulative distribution curves visually presented the difference in these geometric descriptors between furnish types. Data were analyzed to determine the descriptors most useful in predicting the flake alignment potential as well as the board properties of bending modulus of elasticity, shear stress, thickness swell, and linear expansion. Keywords: flake furnish, characterization, image analysis, flake geometry, board properties September 1999 Geimer, Robert L.; Evans, James W.; Setiabudi, Dody. 1999. Flake furnish characterization---Modeling board properties with geometric descriptors. Res. Pap. FPL--RP--577. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 36 p. A limited number of free copies of this publication are available to the public from the Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI 53705--2398. Laboratory publications are sent to hundreds of libraries in the United States and elsewhere. The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin. The use of trade or firm names in this publication is for reader information and does not imply endorsement by the U.S. Department of Agriculture of any product or service. The United States Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, p..

Chlamydomonas IFT70/CrDYF-1 Is a Core Component of IFT Particle Complex B and Is Required for Flagellar Assembly

DYF-1 is a highly conserved protein essential for ciliogenesis in several model organisms. In Caenorhabditis elegans, DYF-1 serves as an essential activator for an anterograde motor OSM-3 of intraflagellar transport (IFT), the ciliogenesis-required motility that mediates the transport of flagellar precursors and removal of turnover products. In zebrafish and Tetrahymena DYF-1 influences the cilia tubulin posttranslational modification and may have more ubiquitous function in ciliogenesis than OSM-3. Here we address how DYF-1 biochemically interacts with the IFT machinery by using the model organism Chlamydomonas reinhardtii, in which the anterograde IFT does not depend on OSM-3. Our results show that this protein is a stoichiometric component of the IFT particle complex B and interacts directly with complex B subunit IFT46. In concurrence with the established IFT protein nomenclature, DYF-1 is also named IFT70 after the apparent size of the protein. IFT70/CrDYF-1 is essential for the function of IFT in building the flagellum because the flagella of IFT70/CrDYF-1–depleted cells were greatly shortened. Together, these results demonstrate that IFT70/CrDYF-1 is a canonical subunit of IFT particle complex B and strongly support the hypothesis that the IFT machinery has species- and tissue-specific variations with functional ramifications