Laminate electrical insulation properties

Its excellent electrical insulation properties lead to its use in wire insulation, in valve holders, in insulated transformers, in hermetic seals for condensers, in laminates for printed ciruitry and for many other miscellaneous electrical applications. 

Glass-reinforced melamine-formaldehyde laminates are valuable because of their good heat resistance (they can be used at temperatures up to 200°C) coupled with good electrical insulation properties including resistance to tracking. 

Although occasionally in demand because of their good electrical insulation properties, aniline-formaldehyde resins are today only rarely encountered. They may be employed in two ways, either as an unfilled moulding material or in the manufacture of laminates. 

The polysulphides are frequently used in casting mixes and to a less extent in coating, laminating and adhesive applications. Their value in casting and encapsulation lies mainly with their low curing shrinkage and flexibility in the cured state. Their tendency to corrode copper and the somewhat inferior electric insulation properties of the blends does lead to certain limitations. 

The third problem associated with water based varnishes is poor electrical insulation properties of the laminate after moisture conditioning. This problem is probably the most critical problem because insulation failures of the laminate can lead to electrical failure of the finished printed circuit board. This property is measured by conditioning the finished laminate in a high moisture environment and then testing the dielectric breakdown strength. ED24574 has excellent insulation resistance. This was achieved by a proprietary resin composition. 

Its excellent electrical insulation properties and heat resistance lead to its use in high-temperature wire and cable insulation, molded electrical components, insulated transformers, hermetic seals for condensers, laminates for printed circuitry, and many other electrical applications. 

Two classes of resins are generally distinguished. Resols prepared with ammonia as catalysts are spirit-soluble resins having good electrical insulation properties. Water-soluble resols are prepared with caustic soda as catalyst. In aqueous solutions (with a solids content of about 70%) these are used mainly for mechanical grade paper and cloth laminates and in decorative laminates. 

Caustic soda is commonly used as the catalyst for the manufacture of resols for mechanical and decorative laminates. However, it is not used in electrical laminates because it adversely affects the electrical insulation properties. For electrical-grade resols ammonia is the usual catalyst, and the resins are usually dissolved in industrial methylated spirits. The use of cresylic acid (m-cresol content 50-55%) in place of phenol yields laminating resins of better electrical properties. 

Bakelite one of the earliest plastics. Thermosetting resins of the phenol-formaldehyde type with high electrical insulation properties. Used with fillers as moulding materials and in laminates. 

As a tme thermoplastic, FEP copolymer can be melt-processed by extmsion and compression, injection, and blow molding. Films can be heat-bonded and sealed, vacuum-formed, and laminated to various substrates. Chemical inertness and corrosion resistance make FEP highly suitable for chemical services its dielectric and insulating properties favor it for electrical and electronic service and its low frictional properties, mechanical toughness, thermal stabiUty, and nonstick quaUty make it highly suitable for bearings and seals, high temperature components, and nonstick surfaces. 

In other areas, POD has been used to improve the wear resistance of a mbber latex binder by incorporation of 25% of Oksalon fibers. Heat-resistant laminate films, made by coating a polyester film with POD, have been used as electrical insulators and show good resistance to abrasion and are capable of 126% elongation. In some instances, thin sheets of PODs have been used as mold release agents. For this appHcation a resin is placed between the two sheets of POD, which is then pressed in a mold, and the sheets simply peel off from the object and mold after the resin has cured. POD-based membranes exhibit salt rejection properties and hence find potential as reverse osmosis membranes in the purification of seawater. PODs have also been used in the manufacturing of electrophotographic plates as binders between the toner and plate. These improved binders produce sharper images than were possible before. 

The dough moulding compounds were originally developed in an attempt to combine the mechanical properties of polyester-glass laminates with the speed of cure of conventional moulding powder. In spite of their somewhat high cost they have now established themselves in a number of applications where a mechanieally strong electrical insulant is required. 

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