Radiation phenol-formaldehyde

Treatment of solid wood over the years for increased utility included many chemical systems that affected the cell wall and filled the void spaces in the wood. Some of these treatments found commercial applications, while some remain laboratory curiosities. A brief description of the earlier treatments is given for heat-stabilized wood, phenol-formaldehyde-treated veneers, bulking of the cell wall with polyethylene glycol, ozone gas-phase treatment, ammonia liquid- and gas-phase treatment, and p- and y-radiation. Many of these treatments led to commercial products, such as Staybwood, Staypak, Im-preg, and Compreg. This chapter is concerned primarily with wood-polymer composites using vinyl monomers. Generally, wood-polymers imply bulk polymerization of a vinyl-type monomer in the void spaces of solid wood. 

MS polymers Phenol-formaldehyde resins Polyimides Acrylates and epoxides, radiation-crosslinkable Rubber adhesives, crosslinking Adhesive films, heat activating Activation temperature variable... 

Cured phenol—formaldehyde resin is less stable towards radiation than is polystyrene. About 108 rad reduce the tensile strength to about 80% of its original value. If the polymers are filled with inorganic materials, their stability is considerably improved. 

In a positive-tone resist, the areas that are exposed to the radiation develop away into the solvent faster than unexposed areas, resulting in a positive-tone image of the mask. The majority of commercial, positive-tone, nonchemically amplified resists used today are variations of the well-known, two-component, diazonaphthoquinone-novolac resist [5]. Novolac is a name generally given to acid-catalyzed phenol formaldehyde condensation polymers of the type shown in Fig. 2. 

Phenol-formaldehyde These are usually filled or reinforced. The addition of several fillers increases the radiation stability significantly, by as much as 100-fold. Filled resins of this type usually show good radiation resistance up to 500 Mrads or higher. (General radiation resistance good.)... 

M.S. Sreekala, M.G. Kumaran, M.L. Geethakumariamma, and S. Thomas, Environmental effects in oil palm fiber reinforced phenol formaldehyde composites Studies on thermal, biological, moisture and high energy radiation effects. Adv. Compos. Mater. 13, 171-197 (2004). 

Phenol-formaldehyde,aniline-formaldehyde, diphenyl oxide-formaldehyde, trioxane, tetrahydrofuran, formaldehyde,and formaldehyde-ketene have been combined with MA to give resinous materials. The reaction between the trioxane and formaldehyde-ketene was initiated by various types of radiation. 

Radiation-induced decomposition or chemical alteration of the dissolution inhibitor restores the solubility of the polymeric matrix. For example, certain polysulfones and polyaldehydes (for general structures, see Chart 5.10) will act as dissolution inhibitors when blended with phenol formaldehyde or cresol formaldehyde resins. 

In general, plastics are superior to elastomers in radiation resistance but are inferior to metals and ceramics. The materials that will respond satisfactorily in the range of 1010 and 1011 erg per gram are glass and asbestos-filled phenolics, certain epoxies, polyurethane, polystyrene, mineral-filled polyesters, silicone, and furane. The next group of plastics in order of radiation resistance includes polyethylene, melamine, urea formaldehyde, unfilled phenolic, and silicone resins. Those materials that have poor radiation resistance include methyl methacrylate, unfilled polyesters, cellulosics, polyamides, and fluorocarbons. 

Chlorinated phenols are common environmental pollutants, introduced as pesticides and herbicides. Studies have been carried out on the potential use of radiation to destroy these compounds as a means of environmental cleanup . While these studies were concerned with mechanisms (and are discussed in the chapter on transient phenoxyl radicals), other studies involved large-scale irradiation to demonstrate the decomposition of phenol in polluted water . Continuous irradiation led to conversion of phenol into various degradation products (formaldehyde, acetaldehyde, glyoxal, formic acid) and then to decomposition of these products. At high phenol concentrations, however, polymeric products were also formed. 

In order to take advantage of the new abrasive grit materials, new and improved bond systems had to be developed. Subsequently, adhesive systems have also come a long way, progressing from fish and animal hide glues to urea-formaldehyde resins, epoxies, phenolic, and radiation-curable systems. This evolution has placed a continuing demand on the adhesive systems used in the manufacturing of abrasive products. 

The most common types of adhesives used today in coated products are hide glues, varnishes, urea-formaldehyde, radiation-curable, and resole phenolic resins. Depending on the severity of the applications, the make and size bond formulations are modified to suit the job at hand. Combinations of the above systems are used to achieve special properties which may give certain products economic and performance advantages. 

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