Exposure Duration
Time spent by a synthetic fabric within the heated chambers of a stenter determines the effectiveness of its thermal stabilization. This period, known as the heatsetting dwell, must be long enough for the entire thickness of the material to reach the required glass transition temperature. It is a primary variable in the production of polyester, nylon, acrylic and elastane blends.
Molecular Orientation
Heat allows the polymer chains inside the fibres to rearrange themselves and release the stresses created during spinning or knitting. The heatsetting dwell provides the necessary window for these chains to form new, stable bonds in a relaxed configuration. If the duration is too short, the fabric will retain a memory of its previous distorted state and will shrink significantly when washed.
Overexposure can lead to yellowing or a loss of tensile strength in the yarns.
Machine Velocity
Calculations for this parameter involve dividing the length of the heated zones by the speed of the transport chain. A stenter with thirty meters of heating capacity running at fifteen meters per minute results in a heatsetting dwell of exactly two minutes.
Quality Outcome
Consistent timing across the entire production lot prevents variations in dye uptake and fabric hand. Maintaining the correct heatsetting dwell ensures that every meter of cloth has the same level of dimensional stability and crease resistance.
