Glass cloths

Grade FR-4, continuous-filament glass cloth with an epoxy resin binder, is similar in all properties to Grade G-10, but so formulated to have at least a UL94 V-1 classification when tested according to UL94. 

Composite-Based Laminates. Grade CEM-1 are laminates with continuous-filament glass cloth surfaces and a cellulose core, all with a flame-resistant epoxy resin binder. With good punching practice, sheets up to and including 2.4 mm (0.094 in.) in thickness may be punched at temperatures not less than 23°C (73°F). These laminates meet UL94 V-0 when tested in accordance with UL94. 

Some types of built-up mica are bound to special paper (qv), silk (qv), linen, muslin, glass cloth, or plastic. These products are very flexible and are produced in continuous wide sheets. These sheets are either shipped in roUs or cut into ribbons, tapes, or other desired shapes (Table 7). 

Blends have also been prepared by dissolving DMPPO in a monomer and then polymerizing the monomer. An example is an epoxy—DMPPO blend prepared by curing a solution of DMPPO in Epon 828 at 85°C with an alurninum—tetramethylguariidine catalyst. Some copolymer formation is observed. The solutions can be appHed to glass cloth before curing to produce prepregs for composites in appHcations such as printed circuit boards (67). 

Table 4. Silane Performance in Glass-Cloth-Reinforced Laminates ...

Waterproof. Waterproofing barrier systems may be either hot- or cold-appHed. The hot-appHed generaUy involve a bituminous material such as asphalt used in conjunction with a reinforcing fabric such as roofing felt, cotton, or glass cloth. Cold-appHed can be bituminous or elastomeric materials either in Hquid or sheet form, with or without fabric reinforcement. Liquid elastomeric treatments include neoprene, polyurethanes, and blends of these or epoxies with bituminous materials. Among the commonly used precured elastomeric sheet materials are neoprene, polyisobutylene, EPDM mbber, and plasticized PVC. Polyethylene and PVC films and nonwoven plastic or glass fabric coated with bituminous materials also find use (78). Because these... 

Glass-reinforced polyester is the most widely used reinforced-resin system. A wide choice of polyester resins is available. The bisphenol resins resist strong acids as well as alkahne solutions. The size range is 2 through 12 in the temperature range is shown in Table 10-17. Diameters are not standardized. Adhesive-cemented socket joints and hand-lay-up reinforced butt joints are used. For the latter, reinforcement consists of layers of glass cloth saturated with adhesive cement. 

Figure 5-30. Expander during hot mechanical running test in Jeannette, Pennsylvania facility. Four inches (102 mm) of insulation is secured to the casing with refractory-type anchors welded to the casing. Final site treatment includes a layer of 1.1 Ib/fF (5 kg/m ) lead foil for acoustic purposes and two outer coats of open-weave glass cloth and emulsion reinforcement, for an aluminum gray color.

Industrial filtration systems may be of many types. The most common type is the baghouse shown in Fig. 29-3. The filter bags are fabricated from woven material, with the material and weave selected to fit the specific application. Cotton and synthetic fabrics are used for relatively low temperatures, and glass cloth fabrics can be used for elevated temperatures, up to 290 C. 

The first commercial applications of polypyromellitimides were as wire enamels, as insulating varnishes and for coating glass-cloth (Pyre.ML, Du Pont). In film form (Kapton) many of the outstanding properties of the polymer may be more fully utilised. These include excellent electrical properties, solvent resistance, flame resistance, outstanding abrasion resistance and exceptional heat resistance. After 1000 hours exposure to air at 300°C the polymer retained 90% of its tensile strength. 

The thermosetting materials are said to be initially linear but are cross-linked by heating in air to a temperature of at least 345°C. It is claimed that they have a useful working range up to 315°C. The materials may be used in compression mouldings powders, as the binder resin in glass cloth laminates and as the polymer base in heat-resistant metal coatings. 

Glass cloth. A range of cloths is available and the finest of these are used in order to obtain the best meehanieal properties. They are, however, expensive in use and they are used only in certain specialised applications such as in the aircraft industry and for decorative purposes. 

Aircraft radomes, ducting, spinners and other parts are often prepared from polyester resins in conjunction with glass cloth or mat. The principal virtue here is the high strength/weight ratio possible, particularly when glass cloth is used. Land, sea and air transport applications account for almost half the polyester resin produced. 

Table 26.11 Mechanical properties of epoxy-glass cloth laminates...

The properties of the laminate are dependent on the resin and type of glass cloth used, the method of arranging the plies, the resin content and the curing schedule. Figure 29.4 shows how the flexural strength may be affected by the nature of the resin and by the resin content. 

Figure 29.4. Influence of resin content on the flexural strength of glass-cloth laminates made with two silicone resins A and B. (After Gale " )...

Of particular importance are the electrical properties of the laminates. These are generally superior to P-F and M-F glass-cloth laminates, as may be seen from Table 29.3P... 

The power factor of typical glass-cloth laminates decreases with aging at about 250°C, which is the main reason for post-curing (Figure 29.5). A power factor drift is, however, observed - under wet conditions and the ratio of power factors between wet and dry conditions is about 3 1. 

Figure 29.5. Effect of aging at 250°C on the power factor of silicone-bonded, glass-cloth laminates.

Property Polyester/ Glass Mat Polyester/ Woven Glass Qoth Epoxy/ Woven Glass Cloth Epoxy/ Filament Wound Glass Rovings... 

The resins known as DAP and DAIP, are cross linked allyl esters of phthalic and rsophthalic acid, respectively. They are notable for rigidity and excellent electrical properties at temperatures up to 4.50" F. Allylic resin-impregnated glass cloth is used in aircraft and missile parl.s. Other... 

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