Shrinkage, Residual Stress and Relaxation
topic
Polyester shrinkage arises from relaxation of oriented amorphous chains above Tg. Boiling water shrinkage (BWS) test: 100°C/30 min immersion measures free shrinkage. Dry heat shrinkage (160°C/30 min). High-shrinkage polyester (HS-PET): BWS 15–20%, blended with FDY in differential shrinkage blend yarns for bulky fabrics. Shrinkage force measured at fixed strain — determines fabric dimensional stability in processing and end-use.
Role
Shrinkage behaviour control is critical for dimensional stability of polyester textiles. Differential shrinkage in blended yarns is an important design tool for creating textured surface effects without texturing machines.