Solvent-Free Ball Milling Combined with Hot Pressing for Fabrication of PLA@LM Functional Composites with Hydrolytic Degradability

Abstract

Abstract The integration of liquid metals (LM) into biodegradable polymer matrices offers a promising route toward functional sustainable composites, while it is often hindered by solvent residues, poor dispersion, and compromised mechanical properties. Herein, we report a solvent‑free, two‑step strategy combining vibrational ball milling (BM) with hot pressing to fabricate PLA@LM composites with hydrolytic degradability. During BM, bulk eutectic gallium‑indium (EGaIn) is in situ broken into micro‑/nanodroplets under high‑energy mechanical shearing, while PLA chains concurrently coat the droplets via hydrogen bonding with the Ga2O3 surface layer, preventing coalescence and further oxidation. Subsequent hot pressing yields a segregated conductive network at low LM loading (<5 wt %). The resulting PLA@LM composite (5 wt % LM) exhibits simultaneously enhanced strength (≈19 MPa) and toughness (≈0.51 MJ/m3), a 120% increase in thermal conductivity (≈0.32 W·m−1·K−1), and a transition from insulating to weakly conductive behavior with a conductivity of 1.33 × 103 S/m and a percolation threshold as low as 0.08 vol %. Moreover, the composite exhibits significant mass loss (>95%) in alkaline aqueous solution (pH = 9) within 8 days. This green, scalable solid‑state approach eliminates organic solvents and additional stabilizers, opening a new avenue for high‑performance, fully biodegradable functional composites.