Wood protective agents

In addition to the old estabfished tar oil from hard coal distillation, newer wood protective oils, containing insecticidal and fungicidal 

Contaminants adversely affect the sensitivity of detection of the active agents, especially in wood extracts the limits of detection are consequently rather high (5 jxg for y-BHC and pentachlorophenol, 2 [xg for monochloronaphthalene). As has been shown by Petrowitz, the inclusion of new types of fluorescent dye in the layers also does not increase sensitivity. The procedures in Section IV, p. 77 may be used for visualising the individual substances. 

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Hager (1995), noting that water-based silicone systems had been used on masonry and concrete to provide water repeUency, investigated their potential as wood protection agents. He mentioned the work of E.G. Rochow, who built a house in 1958 using cedar that was treated with a silicone solution as a water repellent. After 28 years, the silicone protective layer was still sound. Hager treated wood with water-based silicone microemulsions and found that good water repellency could be obtained. 

Indoor pesticides can emanate from a range of sources. They include (1) pesticide application indoors (insecticides, termiticides, wood-protecting agents, etc.), (2) tracking-in of pesticides from outdoors, and (3) impregnated textiles and carpets, treated wood, etc. from an indoor environment itself. 

Polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDDs/PCDFs), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) are now ubiquitous in the environment. Their occurrence in indoor air mainly results from the frequent use of chemical products such as paints, glue, sealants, fire retardants and wood protection agents up to the mid-1980s. Furthermore, PCDDs/PCDFs and PAHs are always formed to some extent during incomplete combustion processes. A list of possible sources is given in Table 1.4-1. 

PAHs Tobacco smoke Combustion processes (fire-places, exhaust of diesel engines, chimneys, candles, barbecue) Paints and glues containing tar oil or bitumen Wood protection agents... 

PCBs Defective electrical capacitors, e.g. in fluorescent light tubes Defective electrical transformers Paintings and varnishes containing flame retardants Plasticizers in sealing materials Wood protection agents... 

A method of estimating concentrations of pentachlorophenol, tetrachlorophenol and lindane in the indoor atmosphere of rooms after application of wood protection agents was given by Zimmerli and Zimmermann (1979). Filter papers were soaked with paraffin oil and exposed in the room. The amount of chemical absorbed per unit of time was proportional to the concentration in air. 

Alkyd paints are used for protection and decoration in virtually all sectors including coatings in the steel, sheet, and metal processing sector, house and decorative paints, do-it-yourself paints, wood varnishes, wood protection agents, and automotive finishes. Alkyd resins are extremely important for corrosion protection coatings. 

Kaurane diterpenes (I) and phenolic amides (II) from Xylopia aethiopica, as well as phenethylalkylketones (III) from Aframomum melegueta are now being patented as leads to new wood-protecting agents. Kaurane diteipenes have previously been found to deter feeding of Lepidopteran larvae (9) and aphids (10) and may thus have a rather broad spectrum of activities, and represent an interesting new class of active compounds. 

Emulsion Adhesives. The most widely used emulsion-based adhesive is that based upon poly(vinyl acetate)—poly(vinyl alcohol) copolymers formed by free-radical polymerization in an emulsion system. Poly(vinyl alcohol) is typically formed by hydrolysis of the poly(vinyl acetate). The properties of the emulsion are derived from the polymer employed in the polymerization as weU as from the system used to emulsify the polymer in water. The emulsion is stabilized by a combination of a surfactant plus a coUoid protection system. The protective coUoids are similar to those used paint (qv) to stabilize latex. For poly(vinyl acetate), the protective coUoids are isolated from natural gums and ceUulosic resins (carboxymethylceUulose or hydroxyethjdceUulose). The hydroHzed polymer may also be used. The physical properties of the poly(vinyl acetate) polymer can be modified by changing the co-monomer used in the polymerization. Any material which is free-radically active and participates in an emulsion polymerization can be employed. Plasticizers (qv), tackifiers, viscosity modifiers, solvents (added to coalesce the emulsion particles), fillers, humectants, and other materials are often added to the adhesive to meet specifications for the intended appHcation. Because the presence of foam in the bond line could decrease performance of the adhesion joint, agents that control the amount of air entrapped in an adhesive bond must be added. Biocides are also necessary many of the materials that are used to stabilize poly(vinyl acetate) emulsions are natural products. Poly(vinyl acetate) adhesives known as "white glue" or "carpenter s glue" are available under a number of different trade names. AppHcations are found mosdy in the area of adhesion to paper and wood (see Vinyl polymers). 

Water Dispersions. Polysulftde products are offered as aqueous dispersions (Thiokol WD-6). These are useful for applyiag protective coatings to line fuel tanks, and for concrete, wood, and ia some cases fabrics, felt, leather (qv), and paper (qv). It has been found that a stable emulsion can be made that contains both LP and manganese oxide curing agent. The emulsion can be thinned and appHed as a spray coating. After it is appHed, water evaporates and the LP cures to form a soHd mbber (13). 

Chemical Reactivity - Reactivity with Water Reacts violently, forming corrosive and toxic fumes of hydrogen bromide Reactivity with Common Materials Attacks and corrodes wood and most metals in the presence of moisture. Flammable hydrogen gas may collect in enclosed spaces Stability During Transport Stable if protected from moisture Neutralizing Agents for Acids and Caustics Hood with water, rinse with dilute sodium bicarbonate or soda ash solution Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

There are known to be about 30,000 disease-causing agents (fungi, viruses, nematodes, bacteria) in 3,000 types of cultivated plants. More than 10,000 species of arthropods (insects, ticks, arachnids) affect agricultural plants and animals. Along with agriculture, pesticides are also widely used in forestry and fisheries, in energy and railroads (to clear plants), in construction (to protect wood structures), etc. 

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