Wood packaging

For example, the lack of good alternatives pushed the U.S. Department of Agriculture in 1998 to recommend the use of methyl bromide to treat wood packaging materials from China. A voracious, nonnative insect pest had been found in such packaging materials in 14 states around the United States. The Asian beetle had no known U.S. predators and could cost the United States more than 41 billion in lost forest product, commercial fruit, maple syrup, nursery, and tourist industries. This beetle was an extremely serious insect, and methyl bromide was the only known effective insecticide. Heat treatment was also suggested, but it proved to be more difficult and expensive (Morse 1998). Therefore, methyl bromide as an insecticide was receiving a reprieve. 

Wood as packaging material is largely used for transport packaging, in the form of crates and pallets. Pallets are a universal and critical part of product transportation. Forty percent of all hardwood lumber produced in the United States is reported to have been made into solid wood packaging. The pallet industry uses approximately 4.4 billion board feet of hardwood lumber and 2.1 billion board feet of softwood lumber for the production of 400 to 500 million solid wood pallets annually. While the amount of new wood pallets manufactured increases slightly, in the same time the percentage of hardwood used is reduced and the recovery of pallets increases. ... 

T. M. Smith, M. Reichenbach, S-A Molina-Murillo, and R. Smith, Potential Effect of International Phytosanitary Standards on Use of Wood Packaging Material, Research report. University of Minnesota, Department of Bio-based Products, 2004. 

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. 

Plywood requirements—includes wood species used, synthetic repair requirements, veneer grades, veneer layers and thicknesses, panel grades with respect to end-use, adhesive bond requirements, panel constmetion and workmanship, scarf and finger-jointed panels, dimensional tolerances, moisture content, and packaging and loading... 

Because of poor therm oform ability, there are relatively few apphcations for polypropylene sheet. New soHd-phase pressure forming (SPPE) techniques are under development for forming PP sheet. Polypropylene is used in coextmded sheet to some extent for food packaging containers. Glass-filled, wood-filled, or other modified polypropylene sheet materials are used in limited automotive apphcations. 

Textile fibers can be air-formed ditectiy into end use configuration by including a shaped condensing surface or, as in the production of pillows, an air-permeable collection package. Aerodynamic web formation is a suitable means for processing brittie fibers such as glasses and ceramics, and stiff fibers such as metaUics and wood. 

Water-borne adhesives are preferred because of restrictions on the use of solvents. Low viscosity prepolymers are emulsified in water, followed by chain extension with water-soluble glycols or diamines. As cross-linker PMDI can be used, which has a shelf life of 5 to 6 h in water. Water-borne polyurethane coatings are used for vacuum forming of PVC sheeting to ABS shells in automotive interior door panels, for the lamination of ABS/PVC film to treated polypropylene foam for use in automotive instmment panels, as metal primers for steering wheels, in flexible packaging lamination, as shoe sole adhesive, and as tie coats for polyurethane-coated fabrics. PMDI is also used as a binder for reconstituted wood products and as a foundry core binder. 

Poly(vinyl acetate) homopolymers adhere well to porous or ceUulosic surfaces, eg, wood, paper, cloth, leather (qv), and ceramics (qv). Homopolymer films tend to creep less than copolymer or terpolymer films. They are especially suitable in adhesives for high speed packaging operations. 

Reclaimed rubber can be used in non-vulcanizing general-purpose NR adhesives. It can be used for insulation, packaging materials, and bonding of polyethylene, canvas, metals and wood. 

There has been a rapid growth of the demand for plastics from less than 20 billion pounds in 1970 to nearly 50 billion pounds consumed in the United States in 1986, mostly due to the substitution of traditional raw materials. All over the world, plastics have replaced metals, glass, ceramics, wood papers, and natural fibers in a wide variety of industries including packaging, consumer products, automobiles, building and construction, electronics and electrical equipment, appliances, furniture, piping, and heavy industrial equipment [57-121]. Consumption patterns of PBAs in some countries are shown in Tabies 1 and 2. 

Organic materials Corrosive vapours are sometimes emitted by organic materials used either in packaging or in the manufactured article, and may be troublesome in confined spaces. Some woods, particularly unseasoned oak and sweet chestnut, produce acetic acid (see Section 18.10), and certain polymers used in paints, adhesives and plastics may liberate such corrosive vapours as formic acid and hydrogen sulphide . It may be necessary to carry out exposure trials, particularly where materials capable of liberating formaldehyde or formic acid are involved. Most corrosion problems of this kind can be prevented by using desiccants, and in many cases they are confined to imperfectly cured materials. For an excellent review see Reference 9. 

Plastics can also be combined with other materials such as aluminum, steel, and wood to provide specific properties. Examples include PVC/wood window frames and plastic/ aluminum-foil packaging material. All combinations require that certain aspects of compatibility such as processing temperature and linear coefficient of thermal expansion or contraction exist. 

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