Annealing effects on structural changes and thermal shrinkage of poly(lactic acid) draw-textured filaments

To control the thermal shrinkage of poly(lactic acid) draw-textured yarns, the annealing effects on structural changes and thermal shrinkage were investigated. Specifically, annealing temperatures of 100 and 160°C and annealing times of 10-50 min per every 10 min were investigated. Differential scanning calorimetry thermograms revealed that filaments annealed at 100°C produced double melting peaks due to crystal imperfections, while those annealed at 160°C for more than 30 min showed a single melting peak. Moreover, wide angle X-ray scattering revealed that annealing at higher temperatures led to better developed crystal structures. Although, the crystal structure developed by annealing birefringence indicated that average molecular orientation was not greatly affected. Yarns annealed at 160°C showed the least thermal shrinkage of 2%, while those annealed at 100°C decreased from 7.9-5.4% with increasing annealing time.