Harmonized System Subheading Classification Rules for Processed Bast Fibers
Harmonized System bast fiber classification relies on physical shive percentage, pectin degradation depth, and mechanical hackling status.
Fiber Bundle Parallelism
Alignment Index
Mechanical orientation of technical flax strands along the longitudinal axis of a sliver defines the physical foundation for predictable drafting during yarn formation. High alignment prevents premature fiber breakage when drawing rollers exert shear stress on the untwisted ribbon. In mill laboratory reports, fiber bundle parallelism measures the proportion of fibers lying within a five-degree angle of the strand axis.
This metric marks the boundary where mechanical processing efficiency yields to fiber length limitations.
Drafting Process
Linear pin drafting frames rearrange overlapping scutched flax bundles into continuous slivers through precise speed ratios between back and front rollers. When sliver passes through intersecting gill boxes, fiber bundle parallelism increases progressively as faller pins comb through the moving mass. Inadequate pin density or incorrect draft ratios cause irregular fiber dragging, which introduces thin places into the sliver.
Mill technicians track sliver regularity on drawing logs to ensure consistent linear density prior to roving frame operations.
Tensile Response
Breaking force in dry and wet spun flax yarns depends heavily on the internal contact area between adjacent elementary fibers. When fiber bundle parallelism reaches optimal values, inter-fiber friction transfers applied tensile loads evenly across the entire cross-section of the yarn. Low parallelism causes localized stress concentration during winding, leading to frequent end breaks on spinning frames.
Spinning room monitoring sheets register yarn strength variations against raw material orientation data to verify batch stability. Mill specifications reject slivers that fall below baseline alignment limits because poor orientation cannot be corrected in downstream ring spinning.