Fluorescence Microscopy of Hardboards

We developed a microscopic technique and used it to explore the internal structure and resin distribution in hardboards. The technique will enable us better to understand the behavior of hard-boards in use. Glycol methacrylate (JB-4 embedding medium) proved to be satisfactory for preparing 10- to 15-μm sections of hardboards with a steel knife on a sliding microtome. This thickness of sample, when viewed in transmitted near-ultraviolet light, allowed a clear visualization of hardboard internal structure and resin distribution through the board thickness. We examined wet-formed and dry-formed hardboard samples. Wet-formed high-density and medium-density boards usually showed fibers consolidated into a compact structure and a uniform resin distribution. Dry-formed high-density boards had a compact structure and medium-density boards a less compact structure; both characteristically showed uneven resin distribution

Dimensional Stability of Acetylated Aspen Flakeboard

This study was conducted to determine if thickness swelling of flakeboards, which is much greater than that of plywood or solid wood, can be improved by chemical modification of the constituent wood flakes prior to board manufacture. The chemical treatment involved acetylation of oven-dry aspen ring flakes with a 50/50 mixture of acetic anhydride and xylene. Thickness swell of treated and control samples was measured by either immersion in water for periods of up to 10 days or exposure to 90% relative humidity for periods of up to 20 days. Treated samples exhibited one-sixth to one-seventh the thickness swelling of controls for the water-soak test. Similar trends were observed for humidity exposure

Electron Microscopy Study of Hardboards

Wet-formed and dry-formed aspen fiber hardboards are examined by transmission electron microscopy to obtain information on the hardboard internal structure and fiber-resin interactions. These factors, when related to strength and dimensional properties of hardboards, may be helpful in determining hardboard quality and suitability for structural use.During hardboard manufacturing, the wood cells break apart at the middle lamella and come in contact again when subjected to pressure during hot-pressing. Occasionally fibers remain attached in bundles. Various stages of middle lamella degradation can be observed. When totally disintegrated, middle lamella appears as dark granular material. Voids of variable size exist in medium- and high-density wet- and dry-formed hardboards. In wet-formed boards the resin (which has high electron opaqueness and appears black) shows even distribution. In dry-formed boards the resin shows uneven distribution; it is present as large accumulations in some areas but absent in others

Strength Tests on Acetylated Aspen Flakeboards Exposed to a Brown-Rot Fungus

Aspen flakeboards made from control flakes and acetylated flakes at 18% acetyl weight gain using phenol-formaldehyde or isocyanate adhesives were subjected to a bending creep test under progressive brown-rot fungal attack with Tyromyces palustris. Deflection of the boards was measured as a function of time until failure. Isocyanate-bonded control flakeboards failed in an average of 26 days, while isocyanate-bonded acetylated boards showed little deflection after 100 days in test. Average weight loss of isocyanate-bonded control boards at failure averaged 6.2%, while the acetylated boards showed about 1.0% weight loss at the end of 100 days. Phenol-formaldehyde-bonded control flakeboards failed in an average of 76 days, while acetylated boards showed little deflection after 100 days in test. Average weight loss of phenol-formaldehyde-bonded control boards at failure averaged 8.6%, while the acetylated boards showed no weight loss after 100 days

VAB Temperature and Humidity Study

In 2012, 17 data loggers were placed in the VAB to measure temperature and humidity at 10-minute intervals over a one-year period. In 2013, the data loggers were replaced with an upgraded model and slight adjustments to their locations were made to reduce direct solar heating effects. The data acquired by the data loggers was compared to temperature data provided by three wind towers located around the building. It was found that the VAB acts as a large thermal filter, delaying and reducing the thermal oscillations occurring outside of the building. This filtering is typically more pronounced at higher locations in the building, probably because these locations have less thermal connection with the outside. We surmise that the lower elevations respond more to outside temperature variations because of air flow through the doors. Temperatures inside the VAB rarely exceed outdoor temperatures, only doing so when measurements are made directly on a surface with connection to the outside (such as a door or wall) or when solar radiation falls directly on the sensor. A thermal model is presented to yield approximate filter response times for various locations in the building. Appendix A contains historical thermal and humidity data from 1994 to 2009

Particle fallout/activity sensor

A particle fallout/activity sensor measures relative amounts of dust or other particles which collect on a mirror in an area to be monitored. The sensor includes a sensor module and a data acquisition module, both of which can be operated independently of one another or in combination with one another. The sensor module includes a housing containing the mirror, an LED assembly for illuminating the mirror and an optical detector assembly for detecting light scattered off of the mirror by dust or other particles collected thereon. A microprocessor controls operation of the sensor module's components and displays results of a measurement on an LCD display mounted on the housing. A push button switch is also mounted on the housing which permits manual initiation of a measurement. The housing is constructed of light absorbing material, such as black delrin, which minimizes detection of light by the optical detector assembly other than that scattered by dust or particles on the mirror. The data acquisition module can be connected to the sensor module and includes its own microprocessor, a timekeeper and other digital circuitry for causing the sensor module to make a measurement periodically and send the measurement data to the data acquisition module for display and storage in memory for later retrieval and transfer to a separate computer. The time tagged measurement data can also be used to determine the relative level of activity in the monitored area since this level is directly related to the amount of dust or particle fallout in the area

Vestiges of the Phoenix: De Quincey, Kant and the Heavens

© Edinburgh University Press, 2011publication-status: Accepte