Acrylic & Modacrylic Staple Fibers, Not Processed for Spinning

Both acrylic and modacrylic fibers fall under the same HTS line (5503300000), so the distinction does not affect classification at the 10-digit level. However, modacrylic fibers — defined as containing 35–85% acrylonitrile by weight — may require accurate fiber content disclosure on commercial invoices and country-of-origin documentation, particularly when end-use certifications for flame-retardant applications are involved.

The fiber must not have been carded, combed, or otherwise processed for spinning. Once it undergoes any such preparatory processing, it shifts to heading 5506, which covers carded or combed synthetic staple fibers ready for spinning. Importers should verify the fiber's processing state with the supplier's technical documentation before classification.