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WARP, WARPAGE. Dimensional distortion in a plastic object after molding or other fabrications. (See DISHED, DOMED.)
WEATHERING. The exposure of plastics outdoors.
WEATHERING, ARTIFICIAL. The exposure of plastics to cyclic laboratory conditions comprising high and low temperatures, high and low relative humidities, and ultraviolet radiant energy, with or without direct water spray, in an attempt to produce changes in their properties similar to those observed on long-time continuous exposure outdoors. The laboratory exposure conditions are usually intensified beyond those encountered in actual outdoor exposure in an attempt to achieve an accelerated effect.
WEB. A textile fabric, paper, or a thin metal sheet of continuous length handled in roll form as contrasted with the same material cut into sheets.
WELD LINE. In a molded article, a zone of defective appearance and/or strength resulting from defective union of two fronts of plastic flowing together within the mold. Sometimes called weld mark.
WINDOW. A defect in a thermoplastic film, sheet, or molding, caused by the incomplete plasticizing of a piece of the material during processing. It appears as a globule in an otherwise blended mass.
WORKING LIFE. The period during which a compound, after mixing with catalyst, solvent, or other compounding ingredients, remains suitable for its intended use.
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