Treesearch

Lignin is an aromatic heteropolymer, abundantly present in the walls of secondary thickened cells. Although much research has been devoted to the structure and composition of the polymer to obtain insight into lignin polymerization, the low-molecular weight oligolignol fraction has escaped a detailed characterization. This fraction, in contrast to the rather inaccessible polymer, is a simple and accessible model that reveals details about the coupling of monolignols, an issue that has raised considerable controversy over the past years. We have profiled the methanol-soluble oligolignol...

This paper summarizes the field performance of three stress-laminated deck timber bridges located in Wisconsin, New York, and Arizona. The deck superstructures of these single-span highway bridges is comprised of full-span glued laminated timber (glulam) beam laminations manufactured with southern pine, hem fir/red maple combination, and/or Douglas fir lumber species. These bridge structures were evaluated as part of a National Timber Bridge Monitoring Program for 2-3 years following construction. Field data collection for these single-span bridges included moisture content, prestressing...

The resistance of natural fiber-filled high-density polyethylene composite specimens to ultraviolet- (UV) and moisture-induced degradation was evaluated by measuring changes to flexural properties. High-density polyethylene (HDPE) served as the polymer matrix for four formulations: two formulations without fiber filler and two formulations one containing wood flour and the other containing kenaf fiber, each added at 50% by weight. Specimens were exposed for 4,000 h to UV radiation and moisture cycling in a laboratory weathering device to simulate the effects of exposure to sunlight and...

In recent years, public concern about indoor mold growth has increased dramatically in the United States. In this study, lactic acid bacteria, which are known to produce antimicrobial compounds important in the biopreservation of food, were evaluated to determine if the same antimicrobial properties can be used to protect wood from mold establishment. Based on biomass measurement, cell-free supernatants from Lactobacillus casei subsp. rhamnosus and Lactobacillus acidophilus grown in deMan Rofosa Sharpe (MRS) broth inhibited 95 to 100 percent growth of three mold - and one stain fungus...

Smooth-planed western redcedar bevel siding was exposed outdoors (preweathered) for 1, 2, 4, 8, and 16 weeks. The weathered boards were separated into two end-matched groups. One group was painted with only primer paint and tested for paint adhesion following preweathering. The second group was painted with a primer and topcoat, exposed outdoors for an additional 20 years, and evaluated during this period for paint cracking and flaking. There was a direct correlation between the amount of time the siding was preweathered and the long-term paint performance. Those boards preweathered for 16...

Juniper is a small-diameter underutilized lignocellulosic material. We evaluated the efficacy of base-treated juniper fiber (BTJF) for cadmium (Cd2+) sorption and the viability of juniper fiber as a sorbent for removing Cd2+ from water. Fourier transform infrared spectroscopy analysis indicated that carboxylate ion is a major functional group responsible for Cd2+ sorption. The apparent ideal sodium hydroxide concentration for base treatment is approximately 0.5 M. A batch sorption isotherm test showed that equilibrium sorption data were better represented by the Langmuir model than the...

Several hardwood demonstration timber bridges were built by the Pennsylvania Department of Transportation in the early nineteen nineties. These bridge superstructures are of the recently developed stress-laminated deck design-type using Red Oak lumber laminations that were pressure-treated with creosote preservatives. This paper will describe the data acquisition system used to monitor seven of these bridge superstructures between 1997 and 2002 and to characterize any effects of cold (winter) temperatures on their structural performance. Prestressing bar forces, a key performance parameter...

Reducing fiber loss is also important to conserve resources and reduce the cost of secondary fibers. This study proposes a deinking selectivity concept that considers both ink removal and fiber yield in determining the performance of deinking operations. The defined deinking selectivity, or Z-factor, is expressed by the ratio of ink removal expressed by the International Standards Organization (ISO) brightness gain or the reduction in relative effective residual ink concentration (ERIC) and the relative fiber rejection loss. Pilot-scale flotation deinking experiments showed that Z-factor...

Hot-melt polyamides are an important market for the dimer acid made from the tall oil fatty acids liberated during the Kraft pulping process. These polyamides bond well to many substrates, but not to polyvinyl chloride (PVC), commonly called vinyl. Dimer-based polyamides made from secondary amines such as piperazine bond well to vinyl. No model for this unique adhesion has been proposed even though many commercial adhesives and other patents have utilized this feature of dimer-based polyamides. This paper examines the validity of models based on mechanical interlock, rheological properties,...

Synthetic resins, such as phenol-formaldehyde (PF), are dominant in wood bonding for exterior and semi-exterior applications because of their excellent water resistance. Replacement of petroleum-based resins with ones having high biomass content would further enhance the environmental preferability of reconstituted wood-based materials. Past studies on using soybean flour in these applications have not led to viable adhesives with high biomass content. However, use of proper denaturation, stabilization, and crosslinking reactions leads to high soybean-content adhesives that can replace PF...