Southern pine, chemically modified

Rowell, R.M. (1977b). Effects of drying method and penetration of chemicals on chemically modified southern pine. Wood Science, 9(3), 144-148. 

Rowell, R.M. (1980). Distribution of reacted chemicals in southern pine modified with methyl... 

Southern pine with a dual treatment of chemical modification with butylene oxide or butyl isocyanate followed by lumen-fill treatment with methyl methacrylate, or southern pine impregnated with methyl methacrylate and polymerized in situ, resulted in modified woods that were resistant to accelerated weathering and to ultraviolet light alone. Physical, chemical, and microscopic changes occurring as a result of ultraviolet light irradiation are described. 

The color of exposed wood in the UV light-only exposure is darker than that of the protected wood for all specimens except those chemically modified with BuO (Figure 3). Light-colored woods like southern pine usually darken on exposure to UV light ( 1, 2). Modification with MMA does not alter the chemical structure of wood, and color changes (darkening) observed are almost identical to those of the control specimens. The Bulso-modified... 

Table 5 shows the increases in cell wall volume resulting from reaction of southern pine with either propylene oxide or acetic anhydride. The oven-dry wood volume after modification with either of these chemicals at approximately 20 WPG is equal to the original wood green volume. This means that chemically modified wood has fewer fibers per centimeter than nonmodified wood. This means that if equal cross-sections of control and modified wood are used for mechanical tests there will be fewer fibers to test in the modified... 

Bonding of chemicals to wood cell wall components--cellulose, hemicellulose and lignin—can change the physical and chemical properties of the wood. For example, reaction of southern pine with simple epoxides results in a modified wood which is resistant to attack by subterranean termites in laboratory tests (1). Wood modified with acetic anhydride, dimethyl sulfate, 0-propiolactone and epoxides are highly resistant to attack by microorganisms in standard soil block laboratory tests (2,3). Southern pine modified by reaction with acetic anhydride and propylene and butylene oxides has a reduced tendency to swell in the presence of water (4). 

Evidence that chemical reaction has taken place with wood cell wall hydroxyl groups is evident from the infrared (IR) spectra of methyl isocyanate-modified southern pine (Figure 3). All samples run in the IR were first milled to pass a 40-mesh screen and extracted first with benzene/ethanol (2/1, v/v) followed by water in a Soxhlet extractor. Any unreacted reagent and isocyanate homopolymer formed during the reaction with wood would be removed by this extraction procedure. The spectrum for unreacted... 

Additional evidence that bonding has occurred in the cell wall of methyl isocyanate-modified southern pine can be seen by considering the volume increase in the treated wood and comparing that to the theoretical volume of chemical added after thorough leaching of the treated wood. If the chemical has entered the wood cell wall, the increase in wood volume as a result of modification should be proportional to the volume of chemical added. 

---