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.
Physical Crosslinks
Structure Association
Supramolecular junctions formed by hydrogen bonding or hydrophobic interactions create a reversible network within thermoplastic elastomers. These physical crosslinks hold the polymer chains together without covalent bonds. Elastane fibers rely on these associations to maintain their shape.
This network structure provides elastomeric recovery.
Thermal Behavior
The breakdown of these non-covalent junctions occurs at elevated temperatures, allowing the polymer to flow and be processed. During heat setting, the physical crosslinks dissociate, which permits the fiber to be stabilized in a new shape. As the temperature drops, the junctions reform and lock in the new dimensions.
If the temperature exceeds the melting point of the hard segments, the fiber loses its recovery permanently.
Mechanical Performance
Elastomeric performance depends on the balance between the hard and soft segments in the polyurethane chain. Hard blocks group together to form domain structures that act as anchoring points, while the soft blocks provide stretch. When tension is applied, the soft blocks extend, and the physical crosslinks prevent the chains from sliding past each other.
This elastic action ensures that the garment recovers its original shape after being stretched.
Processing Constraint
Solvent exposure during chemical finishing can disrupt these physical associations and cause yarn failure. Chlorinated hydrocarbons or certain dry-cleaning fluids swell the hard domains, which degrades the elastic recovery of the fabric. Textile mills must limit exposure to these solvents during wet processing to preserve elastane integrity.
Using aqueous processes under ninety degrees Celsius protects the structural network.