Reduced interfacial thermal resistance in acidic alumina-filled adhesives for heat dissipative applications

Interfacial thermal resistance is crucial for determining the thermal conductivity of composites. Existing studies have explored hybrid filler systems and surface modification of alumina (Al₂O₃) particles for enhancing the thermal conductivities of polymer composites. In this study, highly acidic Al₂O₃ fillers were fabricated by modifying the raw Al₂O₃ surface using citric acid and glucose; the modified Al₂O₃ infiltrated an uncured epoxy adhesive at a concentration of 80 wt.%. The measured thermal conductivities of composites were up to 19.4% and 35.9% higher in glucose-filled and citric acid-filled Al₂O₃, respectively, compared with the raw Al₂O₃ at 25 °C. The experimental analysis and theoretical calculations revealed that the polar functionality on the surface facilitated hydrogen bonding between the filler and epoxy resin, which reduced the interfacial thermal resistance in the composite; this effect was the highest for the carboxyl group. To demonstrate the practical application of the modification technique, the exothermic performance test was conducted and indicated that a light-emitting diode lamp incorporating the citric acid filler-based composite exhibited excellent heat management performance compared to the raw Al₂O₃-applied composite.