Effects of Creosote and Cca on Moisture Movement in Southern Pine and Red Oak

A vapocup apparatus was used to determine rates of moisture movement and water-vapor permeability values for CCA- and creosote-treated red oak and southern pine. The average loading for CCA-treated specimens was 6.4 kg/m3 (0.4 lb/ft3) and the average loading for creosote-treated specimens was 168.2 kg/m3 (10.5 lb/ft3). Specimens were subjected to three different relative humidity conditions: 50%, 75%, and 90%. The rates of mass transfer increased exponentially with increasing relative humidity. The rate of moisture movement was greater for southern pine than for red oak, and greater for CCA-treated specimens than for creosote-treated specimens. The water-vapor permeability values were calculated and the values increased exponentially as relative humidity increased. For both species, CCA-treated specimens had the highest water-vapor permeability values and creo-sote-treated specimens the lowest

Effects of Relative Humidity and Shelf-Life on Selected Properties of Polyvinyl Acetate Adhesive Films

The effects of various relative humidities and shelf-lives on the tensile and thermal properties of a commercial polyvinyl acetate copolymer emulsion (PVAC) adhesive are reported. Adhesive-free films, from both crosslinkable and uncrosslinkable resins at three different shelf-life periods, were formed in an environmental chamber (72% relative humidity). After curing, specimens were cut from the films and divided into experimental units; and each unit was conditioned at a different relative humidity (0, 40, 60, and 90%). Tensile and differential scanning calorimetry tests were conducted after the films reached equilibrium at the various relative humidities. Tensile testing results indicate that at relative humidities greater than 40% the tensile strength and modulus of elasticity of both uncrosslinked and crosslinked films decrease. Shelf-life periods of 1.5, 2.5, and 3.5 months had relatively little effect on the tensile strength and modulus of elasticity values of either crosslinked or uncrosslinked PVAC films as compared to the effects of relative humidity. Regression analysis established that the mechanical properties varied mainly as a function of relative humidity. Differential scanning calorimetry specimens were cut from the same sheets of free film as the tensile specimens. Crosslinked and uncrosslinked specimens from an initial shelf-life period of 1.5 months were tested to determine the effects of relative humidities on the calorimetric properties of the films. The results indicate that relative humidity, especially at levels greater than 40%, affects some of the calorific values obtained from the films

The Effects of Mild Chemical Extractions on the Dimensional Stability of uf and pf Bonded Red Oak Flakeboard

Red oak (Quercus rubra L.) flakes were chemically extracted under mild conditions to determine the effects on red oak flakeboard properties, particularly dimensional stability. Flakes were extracted with weak acetic acid solutions or water under selected treatment pressures and treatment times. Weight loss values of extracted flakes ranged from 4 to 25%. Phenol formaldehyde (PF) and urea formaldehyde (UF) bonded flakeboards were manufactured using either red oak or chemically extracted red oak flakes. Physical and mechanical properties evaluated were modulus of elasticity, modulus of rupture, internal bond, water immersion related properties, and linear expansion. Static bending properties of flakeboards using extracted flakes for both resins, even at high levels of flake weight loss, were similar to boards from unextracted flakes. Internal bond average values for the extracted flakes were lower for the PF boards compared to the controls. Internal bond values for the UF boards were similar to the controls. Dimensional stability values for the PF boards were similar for the extracted and control boards. Dimensional stability tests on the UF boards produced the following results: (1) 2-hour dimensional stability values were improved for the extracted versus control boards; (2) 24-hour dimensional stability values for the extracted boards were similar to the control boards; and (3) linear expansion values for the extracted boards were similar to the control values

Selected Chemical Modifications of Red Oak and Hard Maple Flakes for Flakeboard Manufacturing

The feasibility of using low chemical concentrations, time, and pressure for modifying red oak and hard maple flakes was investigated. Red oak and hard maple flakes were pretreated with water, sodium hydroxide, and acetic acid for different times and pressures to determine weight loss. The chemically modified flakes were processed into flakeboards. Untreated aspen, red oak, and hard maple panels were used as controls. Compared to the hard maple controls, hard maple panels had a reduction in press closing time for all treatment levels. However, a reduction in press closing time for treated red oak compared to red oak controls was evident only for very high weight loss values. Weight loss for red oak and hard maple can be controlled, and it appeared that acetic acid treatments produced better properties for both species compared to sodium hydroxide or water treatments. Mechanical properties were reduced in hard maple for all treatments and in red oak for some treatments, particularly sodium hydroxide treatments. Bending strength values for acetic acid-treated red oak panels were not significantly different from red oak control values. Water and acetic acid treatments for red oak produced similar dimensional stability values compared to red oak controls. This indicated that weight loss can be controlled without detriment to the dimensional stability of the panels. Density, internal bond, thickness swell, water absorption, and linear expansion values for red oak control and acetic acid-treated red oak panels compared favorably with aspen control panels. Density, internal bond, thickness swell, water absorption, and linear expansion values for hard maple control and linear expansion values for water and acetic acid-treated hard maple panels also compared favorably with aspen control panels

Creosote Treatment Effect On Hardwood Glulam Beam Properties

Flexure tests were conducted to determine the effect of creosote treatment on the performance of Combination A northern red oak, yellow poplar, and red maple glued-laminated (glulam) beams. This testing was conducted in accordance with ASTM D198-84 (ASTM 1987a), and the beams were fabricated in accordance with AITC 119-85 (AITC 1986), ANSI/AITC 190.1-83(AITC 1983b), and AITC 200-83 (AITC 1983a). Shear tests were also conducted on samples taken from the beams to determine the glueline shear strength and percent wood failure (WF).There was no significant difference (P < 0.05) between the modulus of rupture (MOR) of creosote-treated and untreated northern red oak beams. However, the MORs of the creosote-treated red maple and yellow poplar beams were significantly (P < 0.05) higher than those for untreated beams. There was no significant difference (P < 0.05) between the treated and untreated apparent modulus of elasticity (MOE) of each species. Therefore, the post-fabrication creosote treatment process from 145.92 to 215.76 kg/m3 (9.11 to 13.47 pcf) average weight retention did not adversely affect the strength (MOR) or stiffness (MOE) of northern red oak, red maple, and yellow poplar Combination A glulam beams.Glueline shear strengths for treated and untreated specimens of each species met or exceeded minimum performance criteria in AITC 200-83. Creosote treatment significantly (P < 0.05) increased glueline shear strength of red maple, but had no effect on the shear strength of red oak and yellow poplar specimens. Mean percentage wood failure of treated shear specimens was significantly (P < 0.05) greater than of untreated specimens in each species. Mean percentage wood failures of red oak and yellow poplar gluelines exceeded AITC 200-83 performance criteria; percentage wood failure of untreated (48%) and treated (59%) red maple shear specimens did not meet AITC 200-83 performance criteria

The influence of cultivation methods on Shewanella oneidensis physiology and proteome expression

High-throughput analyses that are central to microbial systems biology and ecophysiology research benefit from highly homogeneous and physiologically well-defined cell cultures. While attention has focused on the technical variation associated with high-throughput technologies, biological variation introduced as a function of cell cultivation methods has been largely overlooked. This study evaluated the impact of cultivation methods, controlled batch or continuous culture in bioreactors versus shake flasks, on the reproducibility of global proteome measurements in Shewanellaoneidensis MR-1. Variability in dissolved oxygen concentration and consumption rate, metabolite profiles, and proteome was greater in shake flask than controlled batch or chemostat cultures. Proteins indicative of suboxic and anaerobic growth (e.g., fumarate reductase and decaheme c-type cytochromes) were more abundant in cells from shake flasks compared to bioreactor cultures, a finding consistent with data demonstrating that “aerobic” flask cultures were O2 deficient due to poor mass transfer kinetics. The work described herein establishes the necessity of controlled cultivation for ensuring highly reproducible and homogenous microbial cultures. By decreasing cell to cell variability, higher quality samples will allow for the interpretive accuracy necessary for drawing conclusions relevant to microbial systems biology research

Does Christianity teach male headship? : The Equal-Regard marriage and its critics.

Cambridgexvi, 141 p.; 23 cm