Seam Slippage Calibration in ASTM D4034 Testing
ASTM D4034 calibration requires verifying ASTM E4 load cells, 305 mm/min crosshead speeds, pneumatic jaw parallelity, 7 spi sewing, and 6.35 mm curve offset.
Yarn Pullout
Snagging Resistance
Physical damage to the surface of a textile occurs when a sharp object catches an individual loop or strand and draws it away from the fabric plane. Yarn pullout results in a visible loop on the surface and a corresponding tight spot or distortion in the surrounding weave or knit. This defect is particularly common in long-float fabrics or loose knit structures.
Mechanism of Failure
The force of the snag pulls excess length from the adjacent areas of the yarn and concentrates it in one location. While some fabrics can be massaged back into shape, high-twist yarns often lock the pulled loop into a permanent blemish. Resistance to yarn pullout depends on the tightness of the construction and the smoothness of the component fibres.
Continuous filament yarns often show more obvious damage than spun staple yarns because the entire filament stays intact during the pull.
Grading Scale
Visual inspection after a mace snag test determines the severity of the damage.
Product Application
Selecting materials with high resistance to this type of damage is necessary for activewear and children’s clothing. Fabrics that suffer from frequent yarn pullout lose their aesthetic appeal and may eventually develop holes. Testing ensures that the material can withstand the abrasions of daily wear.