Development of high thermal conductivity via BNNTs/epoxy/organic-Si hybrid composite systems

Epoxy as a type of matrix material has been extensively applied for printed circuit boards (PCBs) and electronic packaging industry. In this work, polymer matrix composites, based on epoxy modified by organosilicon resin and filled with boron nitride nanotube (BNNT) were successfully prepared. Effects of the content of BNNT and organosilicon resin respectively on the thermal conductivity (TC) of the composites were investigated. The structure of the composites was analyzed by DSC, SEM and Raman. With the increase of the BNNT content, the TC of the composites enhanced. When the BNNT content rose to 5.0 wt%, the TC value of the composite was 0.45 W/m K, about three times higher than that of neat epoxy (0.1 W/m K). Also, the addition of organosilicon resin to the former epoxy filled with BNNT (5.0 wt% filling content) benefited the improvement of the TC value of the composites, which soared to 0.79 W/m K, almost seven times greater than that of the original epoxy. The TC value of composite was 0.21 W/m K whilst the filing content of AlN reached 10 wt%. The experimental result indicated that the Tg of the composites increases, and their damping decreased. It owed to the forceful interaction between the BNNT and epoxy matrix, restraining the mobility of the epoxy chain characterized by Raman. Raman analysis showed red-shifting in the epoxy/organosilicon/BNNT composite, which evidenced good wetting around the BNNT surface by the polymer due to the effect that the organosilicon resin improved the interface interaction between the BNNT powder and the epoxy resin matrix. This resulted in an increase of the crosslinking density with the filling of BNNT powder, so heat flow network of composite system would be more easily formed. Accomplished the above great improvement, the composites are promising for use as PCB substrates.