Filament tow produced from polymers other than nylon, polyester, acrylic, or modacrylic — including polypropylene, polyethylene, and other specialty synthetics — falls into this residual category. These specialty tows serve niche converting applications in filtration, geotextiles, and industrial nonwovens where the specific polymer's chemical resistance, melting point, or mechanical properties are the selection driver. Because the polymer type is the primary classification determinant, importers should ensure that supplier documentation clearly identifies the fiber-forming polymer by chemical name.

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