Multifunctional hollow fibers of recycled Poly(ethylene terephthalate) (rPET) with flame retardant and antibacterial properties for thermal insulation

The recycling of poly(ethylene terephthalate) (PET) into multifunctional hollow fibers via melt spinning was studied. The flame retardant (FR) and nano-zinc oxide (nano-ZnO) were added to enhance fire resistance and antibacterial properties of the fibers. The effects of fiber extension speed and concentration of FR and nano-ZnO on fiber morphology were examined. The high drawing speeds reduced the fiber diameters as well as the reduction of hollow core sizes. XRD analysis confirmed that the addition of FR increased fiber crystallinity, which was consistent with the improvement of crystallization kinetics observed by DSC, and the higher melt viscosity was inferred from the processing behavior during melt spinning. Flame retardancy improved significantly, with limiting oxygen index (LOI) values exceeding 30% in rPET/FR composites. The ZnO surface functionalization rPET/FR fibers exhibited more than 99.9% bacterial reduction after 24 h against Staphylococcus aureus ATCC 6538 and Klebsiella pneumoniae ATCC 4352. Thermal-conductivity analysis verified the potential of the hollow rPET/FR/ZnO fibers as thermal insulators. • Multifunctional recycled PET fibers with flame-retardant and antibacterial properties were successfully produced. • The hollow structure of fibers promoted the enhanced thermal shielding and char formation improved flame resistance compared with solid fibers. • Recycled PET/PFR hollow fibers coated with nano-ZnO demonstrated effective flame retardancy and antibacterial functionality.