Recyclability of Opaque PET from High Speed Melt Spinning: Determination of the Structures and Properties of Filaments

Characterization of Melt-Spun Recycled PA 6 Polymer by Adding ZnO Nanoparticles during the Extrusion Process

With recent technological advances and the growing interest in environmentally friendly fiber production processes, the textile industry is increasingly turning to the spinning of filaments from recycled raw materials in the melt spinning process as the simplest method of chemical spinning of fibers. Such processes are more efficient because the desired active particles are melt-spun together with the polymer. The study investigates the melt spinning of recycled polyamide 6 (PA 6) fibers modified with zinc oxide nanoparticles (ZnO NPs) in concentrations ranging from 0.1 to 2.0 wt% of the polymer. The extrusion process was optimized under laboratory conditions. An analysis of the effectiveness of the nanoparticle distribution and chemical composition was performed using scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The results of the thermal analysis show an increase in the glass transition temperature of the extruded material from 50.97 °C (raw polymer) to 51.40 °C to 57.98 °C (polymer modified with ZnO NPs) and an increase in the crystallization point from 148.19 °C to a temperature between 175.61 °C and 178.16 °C, while the molar enthalpy (ΔHm) shows a decreasing trend from 65.66 Jg-1 (raw polymer) to 48.23 Jg-1 (PA 6 2.0% ZnO). The FTIR spectra indicate PA 6 polymer, with a characteristic peak at the wavelength 1466 cm-1, but pure ZnO and PA 6 blended with ZnO show a characteristic peak at 2322 cm-1. The distribution of nanoparticles on the fiber surface is more or less randomly distributed and the different size of NPs is visible. These results are confirmed by the EDS results, which show that different concentrations of Zn are present. The mechanical stability of the extruded polymer modified with NPs is not affected by the addition of ZnO NPs, although the overall results of strength (2.56-3.22 cN/tex) and modulus of elasticity of the polymer (28.83-49.90 cN/tex) are lower as there is no drawing process at this stage of the experiment, which certainly helps to increase the final strength of the fibers. The results indicate the potential of modification with ZnO NPs for further advances in sustainable fiber production.

Effect of Recycling PET Fabric and Bottle Grade on r-PET Fiber Structure

PET knitted fabric was melted and cooled by hot pressing at 250 °C to obtain a compacted sheet. Only white PET fabric (WF_PET) was used to study the recycling process by compression and grinding to powder and then melt spinning at different take-up speeds compared to PET bottle grade (BO_PET). PET knitted fabric had good fiber formability and was better suited for melt spinning of recycled PET (r-PET) fibers than the bottle grade. Thermal and mechanical properties of r-PET fibers improved in terms of crystallinity and tensile strength with increasing take-up speed (500 to 1500 m/min). Fading and color changes from the original fabric were relatively small compared with PET bottle grade. Results indicated that fiber structure and properties can be used as a guideline for improving and developing r-PET fibers from textile waste.