Lignin, a byproduct from the chemical processing of lignocellulosic biomass, is a polyphenolic compound that has potential as a partial phenol substitute in phenolic adhesive formulations. In this study, HBr and HI were used as reagents to demethylate an alkali lignin (AL) to increase its hydroxyl content and thereby enhance its reactivity for the preparation of phenolic resins. Analyses by FT-IR, ¹H-NMR and 2D-NMR(HSQC) demonstrated both a decrease in methoxyl groups and an increase in hydroxyl groups for each demethylated lignin (DL). In addition, the molar amounts of phenolic hydroxyls, determined by ¹H-NMR, increased to 0.67 mmol/g for the HI-DL, and 0.64 mmol/g for the HBr-DL, from 0.52 mmol/g for the AL. These results showed that HI, a stronger nucleophilic reagent than HBr, provided a higher degree of AL demethylation. Lignin-containing resins, prepared by copolymerization, met the bonding strength standard for exterior plywood with DL used to replace as much as 50 wt.% of phenol. The increased hydroxyl contents resulting from the lignin demethylations also imparted faster cure times for the lignin-containing resins and lower formaldehyde emissions. Altogether, the stronger nucleophilicity of HI, compared to HBr, impacted the degree of lignin demethylation, and carried through to measurable differences the thermal properties and performance of the lignin-containing PF resins.

WOOD PROPERTY MAPS SHOWING WOOD VARIABILITY IN MATURE LONGLEAF PINE: DOES GETTING OLD CHANGE JUVENILE TENDENCIES?

Knowledge of wood property variation within trees is critical for understanding age effects on wood formation and for improved utilization of forests, and maps provide an effective way to efficiently summarize and visually represent variability. Despite the importance of maps, examples for North American conifers are rare. Most studies focus on plantation grown trees, with the majority examining loblolly and radiata pine. For these species almost all maps can be categorized into two groups related to tracheid differentiation processes. One group includes properties related to secondary cell wall formation, e.g., density, and the second relates to tracheid enlargement, e.g., tracheid length. Maps for trees from natural forests are largely limited to density and are highly variable indicating site effects are large. The degree of variation within a species made it impossible to develop conclusions regarding general patterns of variation as with plantation grown trees. The identified density maps are consistent with the three radial variation patterns defined by Panshin and de Zeeuw (1980) (Type 1 (increase), 2 (decrease then increase), and 3 (decrease)). A focused research effort to better visualize wood property variation is required, particularly for species demonstrating Type 2 and 3 radial density patterns.