Wood products weather-resistant

The most prominent wood adhesives used over the last quarter of a century have been aminoplast and polyphenolic types (2). In the United States, polyphenolic adhesives continue to be predominantly used for production of weather-resistant wood products, such as structural plywoods and flake boards (3). Phenolic resin prices have increased over the past decade, generally paralleling phenol prices. This increase has occurred in part due to a continuing erosion of United States phenol manufacturing capacity and the corresponding increase in availability of phenol from other countries. Any significant increase in the price of oil (the source of phenol) itself or interruption in supply will only compound the problem and raise phenol prices even higher. 

Phenolic adhesives continue to be the most significant adhesives for the production of weather-resistant wood products. The energy crisis of the seventies, the cost of phenol, and the inevitable decline in petroleum reserves have caused the wood industry to focus attention on obtaining adhesive self-sufficiency (1). This concern arises primarily from the questionable longterm availability of resins and secondarily from the economics of adhesive resin use. Ready availability of adhesive resins is critical to the manufacture of bonded wood products. In practical terms, this means that new adhesive systems are needed in which part, or perhaps all, of the petroleum-derived phenolic component is replaced... 

Chemical modification of wood, in which chemical moieties are covalently bound to the wood, offers tremendous potential as a general way of upgrading important wood properties such as biological durability and dimensional stability, and may also provide a route to weather-resistant wood products in the future. Research to date has shown that some types of chemically modified wood appear to at least partially resist the surface effects of weathering. The challenge for the future will be to better understand the factors contributing... 

It is mainly used in the industrial production of rigid polyurethane foams. Many other uses are in the fields of coatings, adhesives, sealants and elastomers such as paints, adhesives, weather-resistant sealing materials and foohvear. There is use also in the production of particle board (bonding of wood) and mould cores for the foundry industry (European Union, 1999). 

The use of PVC wood, which includes PVC foam and PVC/wood flour composite, as an alternative to wood and wood-like products is discussed. Compared with traditional products, the PVC wood is shown to exhibit improved termite resistance and weathering resistance, lower moisture absorption and ease of installation. It is demonstrated that PVC wood can be nailed, screwed, sawed, cut and bonded like wood by conventional tools without any special skills being required. The bending strength of PVC wood is lower, but it can still be used for... 

The wood panels industry heavily relies on the use of synthetic resins and adhesives, as adhesively bonded products of one kind or another constitute about 80% of the wood products on the market today. In short, without adhesives and resins this industry would not exist [1,2]. Among these products a certain proportion of wood panels are manufactured for exterior, weather resistant application. Phenol-formaldehyde (PF) resins, and more recently, phenol-urea-formaldehyde (PUF) resins [3-8] are the most commonly used resins among the leading adhesives for exterior grade wood panels. 

The main advantage of all types of phenolic resin adhesives for wood is their remarkable weather and water resistance. Their main use is then for the manufacture of exterior- and marine-grade wood products, structural or otherwise. 

Resorcinol-formaldehyde resins are cold-setting adhesives for wood structures. Urea-formaldehyde adhesives, commonly modified with melamine formaldehyde, are used in the production of plywood and in wood veneering for interior applications. Phenol-form-aldehyde and resorcinol-formaldehyde adhesive systems have the best heat and weather resistance. 

Industrial finishing systems are applied to a wide variety of substrates, the majority of which are metallic, but they are also applied to paper, wood, wood composites, cement products and plastics. Often a high quality of decoration is required, as well as protection from a number of hazards, such as knocks, abrasions, bending or forming and contact with non-corrosive liquids. Resistance to the weather may be required. Outdoor finishing systems, and many others, are also required to protect metal against corrosion. 

Below-grade walls may be constructed of poured concrete, masonry blocks, or other materials such as all-weather wood or stone. This chapter discusses details for use of poured concrete and masonry foundation because these are the materials most commonly used for new construction. Recently, trade associations such as American Plywood Association (APA) and the National Forest Products Association (NFoPA) have issued publications on designing radon resistance permanent wood foundations. Information on these types of foundations can be found by contacting the appropriate trade association.21... 

Wood modification is a means of altering the material to overcome or ameliorate one or more of its disadvantages. The aim of a modification may be to bring about an improvement in decay resistance or dimensional stability, to reduce water sorption, to improve weathering performance and so on. The term wood modification applies to the application of a process that alters the properties of the material such that during the lifetime of a product no loss of the enhanced performance of the wood should occur. 

Understanding the role of chemical modification of wood and wood surface in controlling the outdoor weathering process is significant to the future use of wood exposed to the outdoors. The role of modification will become larger as greater demands are placed on the newer wood-based products. The future of such modification lies in end-product property enhancement. Permanently bonded chemicals that provide UV stabilization, color control, water resistance, and dimensional stability could enhance outdoor performance greatly. 

Some of the procedures of value for processing of mixed plastic wastes may also be useful for the recovery of value from the laminates used for efficient packaging of food and beverages (e.g., milk cartons, Tetrapaks). A combination of heat and pressure may be employed on a recycle stream of this type of material to fuse the mixed fibrous and resin components into a dense board-like product [31, 32]. This highly weather and insect resistant product, Eco Superwood Plastic Lumber, may be sawn, nailed, drilled, etc., like wood, and it resists rotting in direct contact with the soil without the need for preservatives. 

Plastic lumber is recycled plastics processed such as commingled plastic, polyethylene plastic, and polypropylene plastic. To improve their performances different developments have been used such as specialty additives (lubricants, deoxidizers, etc.). An example is by adding as low as 10 wt% of short glass fiber to these recycled plastics can double their strength. Other fibers used include hemp, flax, and sisal. They are principally extruded other processes are used such as injection and compression molding, to produce products competitive to wood lumber on land and in the water. Compression molding allows for a deep-molded grain and a much more dense board. The density also helps the product resist moisture absorption and improves weatherability. 

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