Thermodynamic Analysis of Hydrolyzed Polyurethane Filament Failure during Dyeing
Hydrolytic polyurethane breakdown during high-temperature dyeing occurs via acid-catalyzed ester cleavage, requiring polyether backbones and strict pH control.
Acid Catalyzed Chain Cleavage
Polymer Breakdown
Chemical degradation of synthetic fibres happens during wet processing when acid exposure initiates the hydrolytic splitting of polymeric bonds. In polyester and polyamide materials, acid catalyzed chain cleavage occurs when protons from acidic finishing baths attack ester or amide linkages in the polymer chains. This chemical event decreases the average polymer chain length and compromises the integrity of the extruded filaments.
Acidic Environment
Concentrated acid residues left on fabric surfaces during high-temperature curing accelerate the breakdown of the polymer structure. Thermal treatments like heat setting or curing of durable-press finishes intensify the action of these residual acids by evaporating water and leaving highly concentrated proton sources on the substrate. Fabric strength decreases as the acid becomes more concentrated.
This hydrolytic action represents a primary risk in cotton-polyester blends finished with acidic catalyst systems.
Structural Degradation
Severe degradation of the internal polymeric network results in localized fabric failure during subsequent mechanical manipulation. Tensile strength drops as fewer continuous chains remain to bear the mechanical loads applied to the yarn. Hand feel becomes harsher due to the accumulation of short polymer fragments that alter the crystallization and flexibility of the yarn.
Finished garments display a susceptibility to tearing along stitch lines where sewing needles create local stress concentration. Laboratory tensile tests according to standard methods confirm the structural loss through a marked reduction in force at break.
Industrial Protection
Thorough rinsing and neutralization after acid treatment prevent the occurrence of unwanted fibre degradation. Alkaline baths containing soda ash neutralize any residual protons before the fabric enters the drying ovens.