Cotton Ply Twist Multipliers in Continuous Reactive Dyeing
Yarn ply twist multiplier controls intra-bundle pore radius; multipliers above 4.0 cause surface ring-dyeing frosting while values under 3.2 provoke migration.
Wet Bulb Steaming
Conditioning Treatment
Exposure of yarn or fabric to a controlled mixture of heat and moisture stabilizes the internal stresses of the fibers. This wet bulb steaming process uses the temperature of a moistened sensor to regulate the humidity of the treatment chamber. It is commonly used to fix the twist in high twist yarns and prevent them from snarling during subsequent processes.
The moisture acts as a plasticizer, allowing the polymer chains to relax into their new configuration.
Temperature Control
Precision in the ratio of water vapor to air is necessary to avoid damaging sensitive fibers. During wet bulb steaming, the difference between the dry temperature and the wet bulb temperature determines the relative humidity of the environment. High humidity ensures that the moisture penetrates the core of the yarn package uniformly.
If the temperature is too high, it can lead to yellowing or a loss of tensile strength in natural fibers.
Dimensional Stability
Relaxation of the internal energy in the fiber reduces the tendency of the fabric to shrink or skew after it is cut. Because wet bulb steaming happens at a lower temperature than pressurized steaming, it is gentler on the material. This method is often applied to wool and wool blends to improve the handle and the drape of the final cloth.
The treated material retains its shape better through domestic laundering.
Dye Fixation
Moisture levels in the fiber must be consistent to ensure that any remaining dye molecules are properly set. In some printing applications, wet bulb steaming provides the necessary conditions for the dye to migrate into the fiber structure. The process is monitored by measuring the weight gain of the material to ensure that the target moisture regain has been achieved.