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.
Micro Polyamide
Filament Dimension
Synthetic polymer filaments manufactured with a linear density below one decitex per filament offer exceptional softness and flexibility. This engineered fiber class, known as micro polyamide, combines the high strength and abrasion resistance of nylon with a lightweight, luxurious hand feel. It is widely used in activewear and premium lingerie.
The fine filament structure also allows for extremely high fabric density, which provides windproof and water-repellent properties.
Textile Behavior
Extremely fine filaments increase the total surface area of the yarn by several times compared to standard nylon. This vast surface area enables rapid capillary action, making the resulting fabric highly effective at moisture wicking and quick drying. However, the increased surface area also reduces the bending stiffness of each individual filament.
This physical change yields a fluid drape and a soft, non-abrasive texture that does not irritate the skin.
Dyeing Characteristic
Achieving deep shades on fine filaments requires higher concentrations of dyestuff because the light reflects differently off the high surface area. The rapid uptake of dye by micro polyamide can lead to uneven coloration if the temperature of the dye bath is not carefully controlled. Leveling agents and a slow heating rate are necessary to ensure uniform distribution of the acid dyes across the yarn cross-section.
Additionally, the fastness properties of dyed fine yarns are typically lower, requiring post-dye fixation treatments.
Finishing Action
Specialized mechanical finishes like emerizing must be applied with low pressure to avoid shredding the fine filaments. Carefully adjusting the sueding rollers prevents fiber damage while enhancing the suede-like hand of the fabric.