Mechanical Strength
Laboratory measurement of the breaking force of a parallel ribbon of fibers provides a standardized index of flax fiber quality. The Pressley bundle strength determines the tenacity of the extracted fibers before they enter the carding and combing stages. This measurement uses a specialized clamping instrument that holds a specific weight of fibers and breaks them under controlled tension.
Chinese mills utilize this index to categorize incoming raw flax into different quality classes for downstream spinning.
Quality Classification
Classification of raw flax relies on tensile testing to ensure that the fiber bundles can withstand the high draft forces of wet spinning. Spinning mills use the Pressley bundle strength to verify that the raw material meets the technical requirements of the buyer’s order. Technicians clamp the fiber ribbon at a zero gauge length to record the maximum breaking force, which is then divided by the bundle weight.
These test results are documented in the mill quality certificate that accompanies each processed batch. Low strength values alert the production supervisor to adjust the loom parameters or redirect the fiber to coarser yarn production.
Spinning Prediction
Yarn break rates during the drafting process can be forecasted by analyzing the initial bundle tenacity of the fiber supply. Flax batches with high Pressley bundle strength produce yarns with fewer thin places and higher tensile consistency. Production logs track this metric to maintain high loom efficiency.
Steady yarn strength increases overall weaving productivity.
