Intermediate Thermal Drying Velocity Profiles for Polyester Cotton Blends
Symmetric nozzle velocity between 18 and 22 m/s during intermediate drying prevents dye migration and maintains shade uniformity in polyester cotton blends.
Fabric Fluttering
Aerodynamic Instability
Uncontrolled vibration of a textile web occurs when high velocity air currents interact with a moving substrate during heat setting or drying. This fabric fluttering creates repetitive stress on the selvedges and can lead to uneven application of chemical finishes. It is most prevalent in low gsm materials or wide width fabrics where the center of the web lacks physical support.
Edge Stress
Turbulent air from the nozzles induces a wave-like motion that travels across the width of the material. Excessive fabric fluttering forces the pins or clips of a stenter to work against lateral tension, which sometimes results in pin holes or fabric detachment. Operators must balance air pressure between the top and bottom nozzles to minimize this movement.
Finish Uniformity
Chemical pick up remains consistent only when the substrate passes through the curing zone in a flat, stable orientation. When fabric fluttering becomes severe, the resulting turbulence causes the resin or dye to pool in the troughs of the waves. This localized variation produces streaks or blotches that become visible only after the material is fully cured and inspected.
Mitigation Strategy
Increasing the mechanical tension in the warp direction often dampens the oscillation of the web. Lowering the fan speed represents another method to reduce fabric fluttering, although this adjustment necessarily extends the required dwell time in the oven.