Air Jet Spun Yarn Mechanics in Elastic Woven Fabrics
Air jet core-spun yarns deliver torque-free, pill-resistant elastic wovens by locking polyurethane filaments inside parallel staple cores bound by vortex wrappers.
Core Grin Through
Core Visibility
Visual defect appearing when the internal filament of a composite yarn becomes visible through the surrounding staple fibre covering. A fabric exhibiting core grin through shows points of high-contrast colour or shine where the elastomeric or high-tenacity centre has displaced its sheath. This condition occurs most frequently in stretch denim or woven fabrics where the core yarn is under high tension during weaving or finishing processes that apply extreme mechanical load.
Causal Factor
Imbalance between the twist multiplier of the sheath and the draft ratio of the core filament causes this separation. When the staple fibres do not sufficiently wrap the core, any bending of the yarn allows the internal component to emerge. Insufficient covering leads to visible spots on the fabric surface after dyeing because the core material often accepts dye differently than the cotton or wool sheath.
Verification Method
Inspection of the finished bolt under standard lighting identifies the severity of the exposure. A mill technician checks the core grin through by stretching the fabric to its maximum functional limit to see if the core pops through the surface. Precise tension control during the spinning process reduces the likelihood of this flaw.
Manufacturing Limit
High draft ratios exceeding 3.5 in elastane cores increase the risk. Poor quality ring spinning frames or worn rubber cots contribute to uneven distribution of the sheath. Proper maintenance of the spinning triangle ensures a consistent wrap.