Poly Sealing Components

In addition to carbon and glass fibers ia composites, aramid and polyimide fibers are also used ia conjunction with epoxy resias. Safety requirements by the U.S. Federal Aeronautics Administration (FAA) have led to the development of flame- and heat-resistant seals and stmctural components ia civiUan aircraft cabias. Wool blend fabrics containing aramids, poly(phenylene sulfide), EDF, and other inherently flame-resistant fibers and fabrics containing only these highly heat- and flame-resistant fibers are the types most frequently used ia these appHcations. 

The visor is a key component of any chemical splash suit. Not only mustthe visor material withstand the effects ofthe chemicals and maintain good visibility, but a good seal between the visor and the suit is essential and the seal to the fabric portion of the suit should be checked frequently. Normally visors are made ofmaterials such as polycarbonates, acrylics, fluorinated ethylene propylene (FEP), and clear poly vinyl chloride. The first two of these are subject to crazing upon contact with some chemicals. Covering these two types of material with a thin layer of FEP is sometimes done to protect them. 

Since they cure by moisture absorption, one-component urethane sealants have joint restrictions and delayed cure characteristics similar to those of one-component poly sulfides, except that urethane sealants cure somewhat faster in similar joints because of greater moisture permeability. Materials are available with package life of up to one year when well sealed from moisture. Catalysts such as 1,2,4-tri-methylpiperazine can speed cure, but at a sacrifice in package life. 

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