Phenolic laminates applications

Phenolic laminates are also used in rocketry and space travel applications as heat shields during exit and re-entry into the earth s atmosphere. At very high temperatures, the surface burns away to leave a carbonaceous layer that glows and which is gradually sacrificed by ablation, protecting and insulating the under-surface for a considerable period. 

Aqueous dispersions are used in fiber bonding, paper coating, friction and abrasive applications, and laminates and wood bonding. Phenolic dispersions improve the strength of latex-contact adhesive applications. Epoxy-modified phenolic dispersions are prepared by dispersion of the phenolic epoxy resin. The systems are used for baked primer applications and bonding requirements. Minimum baking conditions are 20 min at 150°C (26). 

Amino Rosins. Amino resins are the reaction product of an aldehyde with a compound containing an amino (—NH2) group (see Amino Resins). Both urea and melamine react with formaldehyde, first by addition to form methy-lol compounds, and then by condensation to form cross-linked polymers through methylene bridge and methylene ether formation. The cross-linking reactions are exothermic and produce water and formaldehyde as volatile products in reactions similar to resole phenolics, illustrated in equation 3. Urea-formaldehyde and melamine-formaldehyde account for the bulk of the amino resins. Their characteristics include water solubility and unlimited colorability with dyes and pigments. Applications include decorative high pressure phenolic laminates, adhesives in the laminated wood and furniture industries, and as an additive to textile fabrics to impart wash and wear properties. 

In many electronic and electrical applications the internal wiring of the systems is done by printed methods as depicted in Fig. 16-11. The substrates on which the printed wiring is done are usually plastics. Commonly used materials are paper-based phenolic laminates,... 

A grey-pigmented, typically brush applied, surface paste system comprising a thixotropic phenolic resin paste which is acid catalysed (GP 4835) to improve the surface finish of a phenolic laminate where a subsequent decorative paint finish is required. Other limited pigmentation is possible, and recommendations can be provided for spray-gun application. 

A paint system is the only way to achieve a tough, durable and coloured surface for phenolic laminates. Specific applications should be checked with manufacturer. 

Other results relate to a heat-sink-tab solder joint and a metal twist-tab solder joint, both using the SACX alloy on two different single-sided PCB applications. The laminate types were composite glass/paper (CEM-1) and paper phenolic (ERl). The protective coating was rosin-based for both. The failure mechanism was alloy failure therefore, solder joints were labeled D and E, not acceptable. The twist-tab solder joint was lifted and fractured after completing 300 thermal-shock cycles. 

NB Daia for the three important ihermosetting materials (phenolics, aminoplastics and epoxide resins) were not covered in the 1998 review on which the 1997 data was based. The 1987 figures for these materials do include a substantial percentage of use in adhesive, surface coating and laminate applications. 

Because of their favourable price, polyesters are preferred to epoxide and furane resins for general purpose laminates and account for at least 95% of the low-pressure laminates produced. The epoxide resins find specialised uses for chemical, electrical and heat-resistant applications and for optimum mechanical properties. The furane resins have a limited use in chemical plant. The use of high-pressure laminates from phenolic, aminoplastic and silicone resins is discussed elsewhere in this book. 

Laminates have been prepared for the manufacture of chemical plant. They have better heat and chemical resistance than the polyester- epoxide- phenolic- or aminoplastic-based laminates but because of the low viscosity of the resins were not easy to handle. Because they were also somewhat brittle, furan-based laminates have been limited in their applications. 

Laminated beams (glulam), parallam (or LSL) and fingerjoints a flat pressed multilayer wood beam, thiek wood planks constituting the layers, used for structural exterior applications and bonded with PRF (phenol-resorcinol-formaldehyde) cold-setting resins, or MUF cold-setting resins, or even with certain types of polurethanes (although the use of these latter ones is only established in one country and can show creep and temperature-induced creep problems). The indi-... 

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. 

Phenol-formaldehyde (phenolic) plastics The chemical resistance is affected by the phenol used, cresols giving the best acid resistance whilst xylenols are often used to obtain the best alkali resistance. For chemical-resistant applications the fillers used in moulding powder and reinforcing material in laminates should be inorganic, e.g. asbestos or glass. The resins are usually dark in colour. 

Developments in glued laminated structures and panel products such as plywood and chipboard raises the question of the durability of adhesives as well as wood. Urea-formaldehyde adhesives are most commonly used for indoor components. For exterior use, resorcinol adhesives are used for assembly work, whilst phenolic, tannin and melamine/urea adhesives are used for manufactured wood products. Urea and casein adhesives can give good outdoor service if protected with well-maintained surface finishes. Assembly failures of adhesives caused by exudates from some timber species can be avoided by freshly sanding the surfaces before glue application. 

The laminated (RP) fabric, bonded with phenolic plastic incorporating antifriction ingredients and cured under heat and pressure, gives excellent service when properly applied in various applications. This group of bearings has a low coefficient of friction, antiscoring properties, and adequate strength for use in steel mills and other heavy-duty applications and is well established in the industry. 

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). 

Unlike phenol-formaldehyde polymers, the amino resins are not themselves deeply coloured, but are of a naturally light appearance. They can be easily pigmented to give a variety of shades, which leads to application in uses where good appearance is highly valued, for example in decorative tableware, laminated resins for furniture, and modem white electrical plugs and sockets. 

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