PEG Surface Modification of ZnO Nanoparticles Improves Ductility and Absorption-Dominant EMI Shielding in PLA/PBS/Carbon Fiber Composites.

Composites based on biodegradable polymers are attractive replacements for metallic electromagnetic interference (EMI) shields, but their performance is limited by nanofiller agglomeration. In poly(lactic acid)/poly(butylene succinate) (PLA/PBS) composites reinforced with carbon fiber (CF), unmodified ZnO nanoparticles agglomerate above 1 wt %, severely embrittling the material. In this study, ZnO nanoparticles were coated with poly(ethylene glycol) (PEG, 8 kDa) by solution adsorption and incorporated at 0.5-2 wt % into PLA/PBS (80/20) containing 20 wt % CF. FTIR showed a +14 cm-1 shift in the ether C-O-C band (1093 → 1107 cm-1), consistent with adsorption of PEG on the ZnO surface. Fracture surfaces showed uniform sub-micron dispersion, in contrast to the dense interfacial clusters formed by unmodified ZnO at the same loading. At 1 wt % PZ, the composites combined 76.3 MPa tensile strength and 2.35% strain with 71 dB X-band shielding effectiveness, more than three times the 20 dB commercial requirement. The highest shielding, 89 dB, was reached at 1.5 wt %, with absorption contributing more than 90% of the total. Unmodified ZnO required about five times this loading to reach comparable shielding.