Thermal Fixation Dwell Time Calibration for Micro Polyamide Spandex Knits
Calibrate stenter line speed to effective core dwell time above 190°C rather than total chamber residence to prevent spandex degradation and knit shrinkage.
Greige Pre-Setting
Thermal Stabilization
Application of dry heat to synthetic or blended fabrics before the scouring and dyeing stages prevents the formation of permanent creases and ensures dimensional stability. This greige pre-setting locks the polyester or nylon fibres into a flat configuration while the material is still in its raw state. By treating the fabric at this stage, a mill can avoid the distortion that occurs during high temperature wet processing.
Crease Prevention
Thermal memory is imparted to the fabric during the passage through a heated stenter. Because the fibres are set in an open-width state, the risk of developing rope marks or sharp folds during jet dyeing is greatly reduced. Greige pre-setting is mandatory for lightweight fabrics that are prone to curling or edge rolling.
Process Sequencing
Running the fabric through a stenter frame at high temperatures before wet processing stabilizes the yarn structure against the stresses of the dyebath. If greige pre-setting is omitted, the thermal shock of hot scouring liquids can cause uneven shrinkage or permanent rope marks in synthetic materials.
Temperature Control
Precise adjustment of the machine speed ensures that the fabric reaches its glass transition temperature without yellowing the yarn. This stage is a fundamental requirement for maintaining the width and density of technical textiles.