Development of thermal conductive PMMA/BN electric insulating composite material using electrostatic adsorption method

An electrostatic adsorption method can produce composite materials with an arbitrary structure by changing the ratio of the main particles to the adsorption particles. To develop a composite material with both a higher thermal conductivity and an acceptable breakdown strength (Fb: Field of Breakdown), the DC breakdown test and thermal conductivity test of polymethylmethacrylate (PMMA)/boron nitride (BN) composite material were performed. The Fb of the samples increased regardless of the type of BN filler as the pressure increased. The higher bonding force among the composite particles due to a high pressure leads to a higher Fb. The higher orientation probability of the longer direction of BN, which is perpendicular to the field (press) direction, might induce the higher Fb in the high-pressure sample. The thermal conductivity of the sample with a mixture of the agglomerate of the platelet BN and the platelet BN was higher than those of the other BN samples. The longer directions of the platelet BN and the agglomerate of the platelet BN were oriented perpendicular to the thickness direction. These results suggested that the reasonable strength and higher thermal conductivity were due to the orientation of the agglomerate of the platelet BN and the platelet BN mixture by the press.