Rheological Mechanism
The hydrodynamic and frictional force exerted across liquid-softened bast fibre bundles within a drafting zone governs the separation of elementary flax filaments. In linen wet spinning operations, wet drafting shear occurs as roving travels through hot water baths into tightly loaded drafting roller nips. The hot water softens natural pectinaceous binders holding the long bast bundles together, allowing mechanical drafting shear to slide individual ultimate fibres past one another.
This liquid-assisted shearing action reduces linear density smoothly without fracturing individual cellulose filaments.
Temperature Dependency
Thermal and chemical conditions within the wet spinning trough determine pectin plasticity and the resulting drafting resistance. If trough water temperatures drop below sixty degrees Celsius, incomplete pectin softening elevates wet drafting shear to destructive levels, causing bundle snapping and excessive yarn end breaks. Chinese wet spinning mills inject softened, acidified water maintained between sixty-five and seventy degrees Celsius into the troughs, carefully controlling immersion time.
Spinning technicians measure nip pressures on fluted drafting rollers with mechanical gauges, documenting roller loads on maintenance cards. Uniform shear distribution produces fine, smooth yarns suitable for high-count luxury shirting and apparel fabrics.
Quality Parameter
Drafting uniformity dictates subsequent yarn mass regularity and tensile strength values. Excessive shear forces crush brittle bast filaments, generating short floating fibres that accumulate as slubs and thick spots in downstream winding. Yarn testing laboratories monitor mass variance via capacitance instruments, noting thin places and yarn count variation on mill export certificates.
Wet drafting shear control remains the primary determinant of yarn count ceilings in wet-spun linen processing.
