Wood-based materials protection

Hazarika and Maji 2013a, b, 2014a, b, c, d). Dimensional stability, UV protection, and weather resistance are very significant properties for wood-based materials used in exterior applications. Bio-based wood polymer nanocomposites will have superior properties and can be regarded as high-performance material for the future generation. 

Soil contact and fresh water immersion applications present a high deterioration hazard to wood and wood-based products. Preservatives used in these environments must exhibit sufficient toxicity and leach resistance to protect the wood for the intended lifetime of the building or structure, as building components in such environments typically have a stractural or support function and can be difficult to replace in situ. The preservative s active ingredients should penetrate deep into the wood for maximum performance. Thus, almost without exception, only pressure treated materials find their way into high deterioration hazard end uses. 

Uses Deaerating agent in gel coats, laminating compds., epoxy resin-based coatings, casting materials, and mortars for building protection, wood and furniture lacquers Regulatory FDA 21 CFR 175.300... 

Biocides are widely used to protect wood. They should easily penetrate the wood and chemically interact with the cellvdose component, but not affect its adhesive properties. The fact that wood requires protection against microorganisms leads us to the observation that cellulose based plastics are among the synthetic materials most vulnerable to biodegradation. 

Wood packaging is generally unsuitable for direct contact with food as the wood components, in particular resins and tannins, are easily released to food products by leaching or volatilisation. Before their first use, packaging and containers intended for direct contact with food have to be treated with water and solutions of sodium carbonate or sulfites, or the inner surface has to be covered with a protective layer of, for example, polymer-based materials. Possibihties of food contamination are then dependent on the quahty of the protective layer and the type of plastics. An exception is the storage of spirits and wines in oak barrels, where the extraction of wood components to the product is desirable. 

The health and safety issues outlined herein for particleboard also apply to MDE. A special note should be made of the fact that, because the MDF raw material is of dry fiber base, there exists in MDF a large component of very small, broken, dust-like wood fibers. These contribute to the dust concerns in the manufacturing areas, requiring exceUent dust-control systems, good housekeeping, and personal protection. 

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). 

Bis(tri-ra-butyltin) oxide, BusSnOSnBua, is an organotin chemical very effective in, and widely used for, the protection of such cellulosic materials as cotton textiles, wood, and cellulose-based household-... 

Wood is the most commonly used fencing material, and is also, potentially, the most environmentally friendly choice. Unfortunately, most fencing is made from nondurable softwoods, and strong chemicals may have been used to preserve it (see pp.132-133). In fact, as fence panels are rarely in contact with the ground— which is where wood is most at risk from decay— a simple water-repellent stain should protect them. Fence posts are most at risk from decay at ground level, where wood, air, and soil meet. Posts made from oak or cedar are recommended for their natural durability (see alsop.l33). Concrete post bases extend the life of wooden posts and make them easier to replace. 

---