High-tenacity viscose rayon (540310) is defined by a tenacity exceeding a specified threshold in centinewtons per tex, making it suitable for industrial reinforcement applications. Standard single viscose rayon yarn (540331) falls below that tenacity threshold and is used primarily in apparel and decorative textiles. Manufacturer test data confirming tenacity values is the key classification document.

Yes. Single viscose rayon yarn with 120 or fewer turns per meter classifies under 540331 (untwisted or low-twist), while yarn twisted at more than 120 turns per meter — known as high-twist or crêpe yarn — classifies under 540332. This distinction matters because high-twist rayon is used in crêpe fabrics and carries different technical specifications.