Sulfur wood composites

The purpose of this chapter is to demonstrate the potential and limitations of research in the wood-sulfur field. It explores the interaction between the two materials and the properties of the resulting products. Earlier work on preparing sulfur-wood compositions is discussed, followed by descriptions of some of our work during the last 10 years. Finally, the chemical basis for wood-sulfur interaction is explored on the basis of the preceding knowledge. Other aspects of our work, including preparation of larger-scale specimens and application methods and techniques are published in two other papers. 

Miscellaneous. In ore flotation, sodium sulfite functions as a selective depressant. In textile processing, sodium sulfite is used as a bleach for wood (qv) and polyamide fibers and as an antichlor after the use of chlorine bleach. Synthetic appHcations of sodium sulfite include production of sodium thiosulfite by addition of sulfur and the introduction of sulfonate groups into dyestuffs and other organic products. Sodium sulfite is useful as a scavenger for formaldehyde in aminoplast—wood compositions, and as a buffer in chrome tanning of leather. 

The support for a chemical linkage between cellulose and lignin in wood, presented by Hibbert and co-workers (90), is based on their treatment of oak wood with acetic anhydride, glacial acetic acid and catalytic amounts of sulfuric acid. A fraction soluble in dioxane was found to have, after several precipitations, the same composition of lignin, cellulose and pentosan as that of the wood itself. 

In contrast to the relatively limited number of organosulfur compounds in these species, the anal sac secretions of skunks contain large numbers of malodorous compounds, which are very effectively utilized in the defensive behavior of these species. During the early years of capillary gas chromatography, Andersen et al. [108] found that 150 of the 160 components detected in the anal gland secretion of the striped skunk, Mephitis mephitis, contained sulfur. The results of recent chemical studies on North American skunks by Wood et al. [109] are summarized in Table 4. Only three of the compounds reported in this table are common to the secretions of all four skunk species and, in two of these three secretions, the common compound is present in concentrations of about 1% or less. Although it is clear that skunks use their anal gland secretions primarily for defensive purposes, it does not rule out the possibility that the difference in the composition of these secretions could also be utilized for... 

For the total hydrolysis of polysaccharides, trifluoroacetic acid (TFA) has important advantages over sulfuric acid. The reaction time is short and there is no need for conventional neutralization, as TFA is volatile and can be removed by evaporation. Several methods have been developed, depending on the substance to be hydrolyzed. Soluble saccharides (e.g., polyoses) can be hydrolyzed with diluted TFA, while cellulose, pulp, and wood need treatments with concentrated TFA in homogeneous solution. The presence of lignin impedes the hydrolysis of polysaccharides thus, especially for wood samples, an intensive treatment with TFA is necessary, and correction values have to be considered. Several application examples show that the hydrolysis with TFA enables a rapid quantitative determination of the composition of polysaccharides, pulps, and woods. 

The impact of extraneous inorganic matter on the analysis cannot be predicted. Most chemical analysis methods have been optimized for bark-free wood that has an ash content of less than 2 percent. These methods may not be applicable to herbaceous materials where structural silica can increase the ash content to more than 15 percent of the dry weight of the biomass. One potential problem with high ash samples is that inorganic materials, depending on their composition, may neutralize the sulfuric acid solutions used in the hydrolysis steps. The affect of pH changes... 

The chemistry of the most important wood components has been studied for hundreds of years and is well reviewed (2). Wood adhesives and glues are also thoroughly studied. However, the chemistry of the presently leading commercial compositions still involves as much art as science (3). The status of the present knowledge of the properties and chemistry of elemental sulfur (4,5) have been reviewed recently, and those of modified sulfur are reviewed in another chapter in this book. 

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