Phytic acid‑microencapsulated melamine phosphate as additives for flame‑retardant, biocompatible, and antibacterial Lyocell fibers

Lyocell fibers suffer from intrinsic flammability and a persistent trade‑off between flame retardancy and mechanical integrity. Here, a bio‑inspired “core‑shell‑skin” microcapsule architecture is designed. Melamine phosphate (MP) as the flame‑retardant core is coated with a melamine‑formaldehyde (MF) shell, followed by electrostatic assembly of phytic acid (PA) as a functional skin. The resulting PA‑ functionalized microcapsules (PA‑MMP) are blended with Lyocell spinning dope and processed via dry‑jet wet spinning. At 25 wt% loading, the composite fibers achieve a limiting oxygen index (LOI) of 30.5%, which remains 29.5% after 50 washing cycles. The tensile strength reaches 88.89 MPa, overcoming the typical strength loss of additive‑modified fibers. The PA‑rich surface mimics extracellular matrix phosphorylated microenvironments, promoting fibroblast adhesion (relative growth rate 98.7%) and providing antibacterial rates of 94.8% ( Staphylococcus aureus ) and 98.6% ( Escherichia coli ). Char residue analysis further revealed that PA‑MMP‑Lyocell formed a denser and more continuous char layer than MMP‑Lyocell. This work offers a scalable, eco‑friendly strategy to produce high‑performance Lyocell fibers with integrated flame retardancy, mechanical robustness, and biological activity. Download: Download high-res image (200KB) Download: Download full-size image