Resistance termite attack

Mahogany is any of the hardwoods in the family Meliaceae. These trees are found in the Caribbean, Central and South America, Asia, and Africa. The wood resists termite attack, is easy to work, and has a beautiful reddish hue when polished. Its water resistance made it attractive to ship builders, who used it whenever it was available in sufficient amounts. 

Rowell etal. (1987b) produced PF-bonded flakeboard from acetylated southern pine (21.6 % WPG) or aspen (17.6 % WPG) flakes. This was not completely resistant to attack by termites Reticulitermes flavipes) in a 4-week test. It was thought that acetylation was less effective in preventing termite attack than other chemical modifications because cellulose decomposition in the intestines of termites leads to acetic acid formation in any case. 

Particleboards and flakeboards made from acetylated flakes have been tested for resistance to several different t5 pes of organisms. In a 4-week termite test using Reticulitermes flavipes (subterranean termites), boards acetylated at 16 to 17 WPG were very resistant to attack, but not completely so (, 36,37) This may be attributed to the severity of the test. However, since termites can live on acetic acid and decompose cellulose to mainly acetic acid, perhaps it is not surprising that acetylated wood is not completely resistant to termite attack. 

Wih respect to the insecticide activity, Podocarpus macrophyllus is widely known in Japan for its resistance to termite attack. Saeki disclosed in 1970 that the termiticidal activity is entirely due to inumakilactone A (28) and another unidentified compound of similar structure, the former being more active [70]. This second compound was later reported to be nagilactone D (4). 

In preliminary tests, alkylene oxide-treated southern pine (28) was found to be resistant to termite attack and attack from the marine borers, Teredo (shipworm) and Limnoria. 

Biological resistance Easily attacked by insects and fungi Resistance to termites and fungi Rowell, 1997... 

The molecular weight of PF resin affected termite resistance less clearly than decay resistance, but resins with up to 621 Mn gave better termite resistance than larger molecular weight resins. Although total elimination of termite attack was not achieved by any PF resin treatment, activities of termites fed on the treated wood declined at a greater rate than that of starved termites. At 10% of WPG, all treated blocks caused a 100% mortality of termites after 6 or 7 weeks feeding. 

Property enhancement by acetylation has been frequently reported over the years in other reconstituted wood products such as flakeboards, particleboards, and fiberboards [8,9,11,12,59-64]. Table 16 shows the laboratory decay test of low-density acetylated particleboards made from perishable albizzia wood. They were resistant to attack by Tyromyces palustris (brown rot), Coriolus versicolor (white rot), and Chaetomium globosum (soft rot) above 12% WPG. These acetylated boards with 20% WPG also exhibited an improved resistance to attack by the destructive Formosan termite, Coptotermes formosanus, in the laboratory. However, their performance was unsatisfactory in the wet tropics with a higher hazard of termite attack. High resistance to fungal and bacterial attack in acetylated southern pine and aspen flakeboards was evidenced in laboratory and fungus cellar tests [12]. 

The mechanical properties of wood are hardly affected by acetylation. There is no embrittlement since there is no three-dimensional resin network the hydroxyls are replaced by acetyl groups. There is no loss of toughness, and the wood is very resistant to attack by fungi, termites and marine organisms. 

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). 

The natural resins present in native guayule have been extensively studied and include mono-, sesqui-, di-, and triterpene groups, as well as other secondary metabolites (108). Unfractionated guayule resin has shown considerable promise in the areas of wood preservation (in marine and terrestrial environments) (129) and insect antifeedents (termite resistance) (130-132). These resins also show promise as a biobased renewable replacement for petroleum-based monomers and oligomers in adhesives and coatings. Additional profitable uses for the resins include a natural, low toxicity replacement for creosote in wood treatment and for prevention of termite attack. Resin/lignin products, such as additives for phenol formaldehyde resins, may also prove possible. 

Numerous plant species have been reported to be resistant to attack from subterranean termites. Many of these plants and extracts derived from them were tested for leads as potential natural product basexl pesticides. Forty plant and tree extracts reported to be active against termites displayed poor activity against the Formosan subterranean termite at rates < 0.5% wt/wt. Most naphthoquinones were active with a non-polar substitution in the 2-position. Anthroquinones generally had little termiticidal activity. None of the plant extracts or natural products tested were sufficiently active to be considered useful for control of the Formosan subterranean termite without structural modification. 

Saeki I, Sumimoto M, Kondo T 1971 The role of essential oil in resistance of coniferous woods to termite attack. Holzforschung 25 57-60... 

Polystyrene is resistant to termite attack, only foamed polystyrene is attacked [32]. ABS is attacked by some termite species [32]. 

The available assessments regarding FIFE and PCTFE vary some mention termite attack, others classify huoropolymers as resistant [32]. 

Epoxy resins are classified as resistant. However, there are indications of termite attack [32],... 

Imamura, Y. and Nishimoto, K. (1986). Resistance of acetylated wood to attack by subterranean termites. Wood Research Kyoto, 72, 37 4. 

Rowell, R.M., Hart, S.V. and Esenther, G.R. (1979). Resistance of alkylene-oxide-modified southern pine to attack by subterranean termites. Wood Science, 11(4), 271-274. 

All laboratory tests for biological resistance conducted to this point show that acetylation is an effective means of reducing or eliminating attack by soft-, white-, and brown-rot fungi, tunneling bacteria, and subterranean termites. Tests are presently underway on several lignocellulosic composites in outdoor environments. 

Compreg is highly resistant to decay and attack by termites and marine borers (52). Its electrical and acid resistances are also real high. 

Nevertheless, cellulose fatty esters with low DS values show other qualities, such as a high hydrophobicity. The development of water-repellent cellulosic materials (i.e., cotton, wood), has led to interesting applications in the textile and wood industries. For instance, the direct esterification of timber with fatty acids (and their derivatives) has resulted in extraordinary outdoor durability and resistance to biological attack (e.g. rotting, termites). Industrial exploitation of this technology has recently been conducted in France [WoodProtect by Lapeyre (Magne et al., 2003)]. In this case, the water-repellence conferred to wood and the lack of recognition from predator enzymes account for these properties. 

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