Properties of thermally conductive silicone rubbers filled with admicellar polymerized polypyrrole‐coatedAl2O3particles

Abstract Polypyrrole (PPy) nanolayers were introduced on the surface of alumina (Al 2 O 3 ) particles via admicellar polymerization. The properties of silicone rubbers (SRs) filled with PPy‐coated Al 2 O 3 and pristine Al 2 O 3 as thermally conductive fillers were studied and compared. The results demonstrate that the addition of PPy‐coated Al 2 O 3 leads to a better interfacial compatibility but lower cross‐linking density of the composites than pristine Al 2 O 3 . The improvement in the compatibility and the decrease in the cross‐linking density are paradoxes in affecting mechanical properties. The improvement in the compatibility shows a slight predominance on the strength at low‐filler contents. Lower cross‐linking density of modified‐Al 2 O 3 /SR composites led to a better processing performance and a higher maximum filler loading amount than the pristine Al 2 O 3 /SR composites, which is beneficial to increasing the thermal conductivity and maintaining a relatively good strength. The PPy‐coated Al 2 O 3 /SR composite with 83 wt% filler content has a thermal conductivity of 1.98 W/(m K) and a tensile strength of 2.9 MPa, and the elongation at break was 63%. Functionalized fillers by admicellar polymerization used in the fabrication of filler/SR composites not only improve the interfacial compatibility but also optimize and expand the functions of the composites, which has great significance for the production and application of thermally conductive SR in some branches of industry (automotive, electrical engineering, etc.) in the future.