Interfacial Engineering and Property Investigation of Melt-Polycondensed Poly(Lactic Acid)/Epoxy-Functionalized Nano-Hydroxyapatite Composites

Poly(lactic acid) (PLA)/nano-hydroxyapatite (nHAP) composites show broad potential for biomedical applications; however, poor interfacial compatibility between the two phases remains a key bottleneck limiting their performance. In this work, PLA prepared via melt polycondensation using l -lactic acid as the feedstock was employed as the matrix. Epoxy-functionalized nano-hydroxyapatite (cnHAP) was obtained through surface modification of nHAP, and PLA/cnHAP composites with different mass ratios were fabricated by melt blending. XPS results indicate an epoxy grafting degree of 17.46% for cnHAP, which effectively suppresses particle agglomeration. The PLA/cnHAP composites achieved an impact strength of 710 J/m 2 , representing a 68.65% increase relative to neat PLA. Mechanistic analysis suggests that the covalently bonded interface promotes efficient stress transfer across the phases, induces pronounced plastic deformation of the matrix, and dissipates impact energy synergistically via crack deflection and matrix yielding. In addition, the thermal stability and thermal properties of the composites are also improved synergistically, providing insights for interfacial engineering design of PLA-based composites. Summary Epoxy-cnHAP (17.46% grafting) forms an interlayer and limits agglomeration. PLA/cnHAP impact strength: 710 J/m 2 , +68.65% versus neat PLA. Toughening via crack deflection and matrix yielding; rough fracture surface. Improved thermal and thermophysical properties via interfacial design.