Treesearch

Chromated copper arsenate (CCA), the most widely used wood preservative of the past 50 years, has been replaced for most uses with alkaline-copper systems such as alkaline copper quaternary (ACQ), copper azole (CuAz) and micronized copper quaternary (MCQ). Preliminary research using high-temperature, high-humidity environments have shown that some of these wood preservatives are more corrosive than CCA, although it is unclear how the results of these extreme tests correlate to performance at temperatures and humidities seen in-service. Recently, the authors developed an electrochemical...

Moisture balance models for indoor humidity have been developed and used by researchers and practitioners to generate realistic interior humidity conditions for hygrothermal analysis of building envelopes and to analyze humidity levels and moisture production rates. This paper reviews moisture balance models for residential indoor humidity in cold-climates. We provide background on various simplified approaches to handling water vapor exchange (buffering) with hygroscopic materials in contact with indoor air. We discuss the application of models in actual occupied buildings, comparing...

In this study, Raman spectroscopy was used to investigate the spatial distribution of cellulose nanocrystals (CNCs) in extruded polypropylene (PP) filaments. Raman maps, based on cellulose and PP bands, obtained at 1 micron spatial resolution showed that the CNCs were aggregated to various degrees in the PP matrix. Of the three composites analyzed, two showed clear existence of phase separated regions – Raman images with PP strong and cellulose absent or vice versa. For the third composite, the situation was slightly improved but a clear transition interface between the PP-abundant and...

Near-IR surface enhanced Raman scattering (SERS) spectra of spruce Wiley milled-wood (WMW) and milled-wood lignin (MWL) adsorbed on the silver nano and micro-particles were obtained recently in our laboratory. When the SERS spectra of wood and MWL were compared they were found to be almost identical which suggested that the signals from the carbohydrate components were absent in the WMW SERS spectrum. This was also supported by the fact that no SERS spectrum of cellulose could be obtained under these conditions. Therefore, lignin could be selectively studied in the presence of other wood...

Two new methods based on FT-Raman spectroscopy, one simple, based on band intensity ratio, and the other, using a partial least-squares (PLS) regression model, are proposed to determine cellulose I crystallinity. In the simple method, crystallinity in semicrystalline cellulose I samples was determined based on univariate regression that was first developed using the Raman band intensity ratio of the 380 and 1096 cm-1 bands. For calibration purposes, 90% crystalline Whatman CC31 and cellulose mixtures with crystallinities in the range 12-72% were used. When the intensity ratios were plotted...

Reductions in hygroscopicity, increased dimensional stability and decay resistance of heat treated wood depends on decomposition of a large portion of the hemicelluloses in the wood cell wall. In theory, these hemicelluloses are converted to water and volatile furan-type intermediates that can polymerize in the cell wall. Reductions in hygroscopicity and improved dimensional stability of acetylated wood depends on esterification of the accessible hemicelluloses in the cell wall reducing hydrogen bonding with water and bulking the cell wall back to its green volume. Stability is not 100%...

The hardnesses of secondary cell wall laminae (SCWL) and compound corner middle lamellae (CCML) in wood were measured at indentation strain rates between approximately 7×10-4 s-1 and 20 s-1, using a new method called broadband nanoindentation creep. The wood was subsequently modified with ethylene glycol (EG) and the properties were re-measured. The SCWL and CCML responded differently to this modification: in the SCWL, hardness decreased uniformly by a factor of 3.7 ± 0.3 across all strain rates, whereas in CCML, the modification had a similar effect at low strain rates. However, at high...

The aim of this study was to investigate safer, more inexpensive chemicals derived from sodium silicate that can be used to protect wood against fungal degradation. Desiccant and surfactant properties of sodium silicate-derived products have been used since the early 19th century and may find application for wood decay protection. In our study, wood was impregnated with 19.5% sodium silicate and acidified with 2.5% phosphoric acid for 2 da to produce polysilicic acid. After 2-wk daily water leaching, leached specimens had 0.2% weight loss by a brown-rot fungus, Gloeophyllum trabeum, and...

In an effort to encourage the development of value-added engineered applications for small-diameter round timber, research is being conducted at the US Forest Products Laboratory to develop and verify design guidelines for connections with specific application to round timbers. The objective of this study is to provide potential users with a number of viable connection options applicable to the fabrication of engineered, round-timber structural components and systems. Target uses include trusses, built-up flange beams, and space frames. This article presents information on a mortised...

Nanotechnology has the potential to affect the field of wood preservation through the creation of new and unique metal biocides with improved properties. This study evaluated leachability and efficacy of southern yellow pine wood treated with copper, zinc, or boron nanoparticles against mould fungi, decay fungi, and Eastern subterranean termites. Results showed that nanocopper with and without surfactant, nanozinc, and nanozinc plus silver with surfactant resisted leaching compared with metal oxide controls. Nearly all nanoboron and boric acid was released from the treated wood specimens...