Enhanced thermal conductivities and decreased thermal resistances of functionalized boron nitride/polyimide composites

Abstract Fluorine-containing polyimide (PI) with low dielectric constant ( e ) value was firstly synthesized by a polycondensation reaction of 4, 4-(hexafluoroisopropyl) diphthalic anhydride (6FDA), 1, 3, 4-triphenyldiether diamine (APB) and 1, 3-bis(3-aminopropyl) tetramethyldisiloxane (GAPD). γ-glycidoxypropyltrimethoxysilane (KH-560) and aminopropylisobutyl polyhedral oligomeric silsesquioxane (NH 2 -POSS) were synchronously performed to functionalize the surface of boron nitride ( f- BN) fillers, which were then utilized as thermally conductive fillers to fabricate the corresponding f- BN/PI composites. NH 2 -POSS was successfully grafted on the surface of BN fillers. All the f- BN/PI composites presented better thermal conductivities, dielectric and thermal properties than those of BN/PI composites at the same addition of BN fillers. The obtained thermal conductivity coefficient ( λ ) of the f- BN/PI composites with 30 wt% f -BN was 0.71 W/mK, higher than that of BN/PI composites with 30 wt% BN ( λ of 0.69 W/mK). Modified Hashin-Shtrikman model demonstrated that f -BN possessed relatively lower thermal resistance with PI matrix. Meantime, the corresponding e and dielectric loss tangent (tan δ ) value of the f -BN/PI composites was decreased to 3.32 and 0.004, respectively, lower than that of BN/PI composites with 30 wt% BN ( e of 3.77 and tan δ of 0.007). Moreover, the corresponding heat resistance index ( T HRI ) and glass transition temperature ( T g ) of the f -BN/PI composites was further enhanced to 280.2 °C and 251.7 °C, respectively.