Abstract
The addition of high thermal conductive filler particles such as boron nitride, aluminum nitride, or carbon fiber is an effective way to increase the thermal conductivity of polymeric materials for the industrial applications such as electronic packaging materials, encapsulants, and thermal fluids among others. The effects of particle dispersions, concentrations, and the interactions between BN and polymer matrix on the viscoelastic properties of the boron nitride (BN)/polydimethylsiloxane (PDMS) composites prepared by mechanical mixing are investigated using oscillatory shear rheology. Both untreated and plasma treated boron nitride (BNP) particles with hexafluoropropylene oxide monomers have been used in this study. The addition of the plasma treated BN particles to the PDMS matrix decrease significantly the complex viscosity as well as storage and loss modulus of the composites due to the reduced interfacial energy between the surface of BNP and PDMS chains. For the PDMS/BN and PDMS/BNP composites, the maximum volume packing fraction (sim0.4) of the particles has been determined from the complex viscosity as a function of the frequency. Additionally, the shear-induced alignment of the BN particles dispersed in the PDMS matrix decreases the viscoelastic properties of the composites with the irregular oscillations which is related to the network formation of dispersed BN particles at the higher volume fractions ( > sim0.2).