Quantifying Physical Degradation Limits in Synthetic Elastomeric Knits
Thermal setting over 190°C and jet nozzle pressures above 0.30 MPa degrade polyurethane cores, causing permanent set and elasticity loss in synthetic knits.
Segmented Polyurethane
Block Copolymer
Synthesis of high-performance elastomeric fibers relies on the combination of rigid and flexible molecular units. Within the synthetic fiber industry, segmented polyurethane describes a block copolymer consisting of alternating soft macroglycol blocks and hard diisocyanate-urea blocks. This specific chemical structure provides the unique combination of high stretchability and high recovery force.
These properties make it the primary material for manufacturing elastane and spandex yarns used in modern stretch apparel.
Elastic Performance
Mechanical recovery of stretch fabrics depends directly on the behavior of these alternating block regions. The soft blocks of the segmented polyurethane extend easily under tensile force, while the hard blocks act as physical crosslinks that pull the chain back to its original shape. This microscopic action prevents permanent deformation of the fabric during active wear.
Mill inspections verify the elastic recovery of the finished knit through cyclic extension tests.
Heat Stability
Thermal limits of these materials are determined by the melting point of the hard domains. Industrial finishing processes must remain below this temperature to prevent structural collapse. Proper temperature control ensures that the fabric retains its elastomeric properties.
Chemical Resistance
Environmental factors such as ultraviolet light and pool chlorine can degrade the polymer chain over time. Modern formulations incorporate stabilizers to protect the segmented polyurethane from this chemical breakdown. This ensures the garment remains elastic throughout its intended lifespan.