Determination of Wet Spun Flax Yarn Linear Density and Mechanical Properties
Wet spun flax linear density and mechanical properties depend on strict moisture regain control, hot water pectin drafting, and CRE tensile evaluation.
Uster Capacitive Testing
Dielectric Measurement
Electronic sensor technology measures changes in electrical capacitance as spun yarn passes through an active measuring gap to quantify mass variations. In linen spinning laboratory analysis, Uster capacitive testing measures cross-sectional mass irregularity, thin places, thick places and neps in flax yarn packages. The method governs spun yarn evenness grading and bobbin quality classification, ending at the analytical boundary where high yarn moisture content distorts capacitance readings.
Signal Analysis
The testing instrument pulls yarn through two parallel sensor plates at high testing speeds. Because cellulosic flax fibre and air possess different dielectric constants, variations in yarn mass alter the capacitance signal across the gap. The instrument converts these dielectric fluctuations into continuous mass variation curves, calculating coefficient of variation percentage and thin or thick place counts per kilometre.
Flax yarn presents challenges for capacitive measurement because irregular moisture regain creates dielectric noise that can mimic mass variations. Technicians must condition yarn packages in standard atmospheric conditions for twenty-four hours before testing to ensure stable dielectric properties across the sample lot.
Testing Limit
Laboratory test reports provide standardized yarn evenness values used to trade yarn lots globally. Unconditioned yarn samples produce inaccurate capacitance readings that invalidate laboratory quality reports.