Effect of Melt Spinning Variables on the Structural Changes of Recycled and Bottle Grade Filament Yarn PET

In the present work, recycled polyethylene terephthalate (R-PET), virgin fiber grade PET (FG-PET) and bottle grade PET (BG-PET) chips were spun on a high spinning speed machine into filament yarns and the influence of high-speed spinning process at the speeds of 3000 and 3500 m/min and the spinning temperatures of 280, 285 and 290 °C on the fiber properties was studied. The increase in the take-up speed increased the density, optical birefringence, crystal size, amorphous and crystal orientation, tenacity and initial modulus of recycled-PET and bottle grade filament. The study on the intrinsic viscosity (IV) showed that the recycling process resulted in decreasing the molecular weight of polymers and narrowing the molecular weight distributions. At higher spinning temperatures, the crystallinity, crystal size, tensile and intrinsic viscosity values decreased but the shrinkage increased. In this part of the study, it was found that the R-PET can be a good candidate for using in high-speed melt spinning processes, and the filaments with proper confidants were received from the recycled-PET.