Enhanced Spinning Properties of Chain‐Extended Flame‐Retarded Multiple‐Recycled PET/Cloisite 30B Nanocomposite

This study examines the development of flame‐retardant and spinnable composites using multiply recycled‐recycled polyethylene terephthalate (rrPET), modified with zinc phosphinate (ZPi) and Cloisite 30B C30B (C30B). To address the deteriorated spinnability of rrPET, 0.4 wt% of an epoxy‐based chain extender (CE) was incorporated, significantly improving melt strength and viscoelastic properties. Ten formulations were prepared based on Taguchi experimental design. The optimal composition (containing 4.5 wt% ZPi and 1 wt% C30B) achieved a limiting oxygen index (LOI) of 28.03%, indicating notable flame retardancy. Structural and rheological analyses showed effective nanoparticle dispersion and interaction, resulting in improved chain entanglement and processability. The intrinsic viscosity (IV) increased from 0.376 to 0.596 dL/g, confirming substantial recovery in molecular weight. Thermogravimetric analysis revealed an increase in char residue from 0.73% to 8.02%, while crystallinity remained relatively unchanged. Mechanical tests indicated that CE‐modified rrPET fibers reached a tenacity of 0.276 N/tex and elongation at break of 38.56%. Although tensile strength slightly decreased (0.169 N/tex), C30B inclusion enhanced ductility, raising elongation at break to 42.43% due to improved flexibility and interfacial bonding. Overall, the synergistic use of CE, ZPi, and C30B led to a structurally optimized rrPET composite with enhanced thermal stability, flame resistance, and spinnability.