Applications of phenolic laminates

Although phenolic resins are too dark for use in the surface layers of decorative laminates these resins are employed in impregnating the core paper. In these cases a melamine-formaldehyde resin is used for impregnating the top decorative layer. Phenolic laminates have also been used in aircraft construction and in chemical plant. 

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The main engineering applications of phenolic resins are laminates, foundry and friction materials. In the electrical laminating field, phenolic resins are used to impregnate kraft paper for the production of insulation boards, printed circuits and transformer bushings. The resin used in this case is usually based on cresol or a substituted phenol and used in a water/alcohol solution. The properties obtained would be a function of the reinforcement and the characteristics of resin used, eg high or low molecular weight. 

Phenolics are also used in a variety of other applications such as adhesives, paints, laminates for building, automobile parts, and ion exchange resins. Global production of phenol-formaldehyde resins exceeded 5 billion pounds in 1997. 

Phenolic phenol formaldehydes (PFs) are the low-cost workhorse of the electrical industry (particularly in the past) low creep, excellent dimensional stability, good chemical resistance, good weatherability. Molded black or brown opaque handles for cookware are familiar applications. Also used as a caramel colored impregnating plastics for wood or cloth laminates, and (with reinforcement) for brake linings and many under-the-hood automotive electricals. There are different grades of phenolics that range from very low cost (with low performances) to high cost (with superior performances). The first of the thermosets to be injection-molded (1909). 

Applications for cold-setting, wood-laminating adhesives initially followed the same approach (47) used for laminating resins from western hemlock (38) (i.e., reaction of tannin with phenol-resorcinol-formaldehyde prepolymers). Improvements resulted through the application of Kreibich s Honeymoon technique (48) wherein one side of the material to be bonded is treated with resin and the other with catalyst. One of the preferred systems (49) was phenol-resorcinol-formaldehyde or tannin-resorcinol-formaldehyde at pH 8 with extra paraformaldehyde on the A-side and tannin at 53% solids or tannin-resorcinol-formaldehyde at pH 12 on the B-side. Such resin systems are currently used to laminate eucalyptus or pine in most South African timber-laminating plants. 

Bisphenol A. One mole of acetone condenses with two moles of phenol to form bisphenol A [80-05-07], which is used mainly in the production of polycarbonate and epoxy resins. Polycarbonates (qv) are high strength plastics used widely in automotive applications and appliances, multilayer containers, and housing applications. Epoxy resins (qv) are used in fiber-reinforced laminates, for encapsulating electronic components, and in advanced composites for aircraft—aerospace and automotive applications. Bisphenol A is also used for the production of corrosion- and chemical-resistant polyester resins, polysulfone resins, polyetherimide resins, and polyarylate resins. 

Polycondensation adhesives based on phenol or phenol derivates with formaldehyde are mainly used in the production of wooden constructions (in woodworking one traditionally talks of glueing instead of bonding ), for example, in the manufacturing of laminated bonds (plywood, chipboard, fiber board, beams). Since in these applications, the adherends are able to absorb the water developing during the polycondensation reaction, the processing occurs in heated presses to enable the application of the necessary contact pressure at the required temperature (Section 7.2.4). For applications in nonindustrial fields these adhesive are practically unimportant. 

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