Effects of thermal conductivity on dielectric breakdown of micro, nano sized BN filled polypropylene composites

In this work, a range of polypropylene (PP) based composites filled with micro or nano sized boron nitride (BN) particles at different loadings (0, 3, 6 and 9 wt%) were manufactured to investigate effects of thermal conductivity on surface dielectric breakdown (SDB). In addition to thermal conductivity measurement of various samples, thermal dissipation was also discussed to analyze the relationship between them. Meanwhile, in order to evaluate SDB strength of the manufactured samples, time to SDB, erosion depth and weight loss of the polymeric samples were measured through the test. Obtained results show that thermal conductivity of the doped PP composite is obviously improved. The increased thermal conductivity results in improvement of thermal dissipation ability, which contributes to inhibition of SDB occurrence. Thermal conductivity, thermal dissipation ability and SDB strength all represent positive correlation to filler loading level. More importantly, compared with nano-BN filled PP samples, PP/micro-BN samples can obtain higher thermal conductivity, better thermal dissipation ability and higher SDB strength at the same filler content. Experimental validation was also conducted with dc bulk dielectric breakdown (BDB) measurement of various samples. It is concluded that introduction of nano-BN filler into base resin favors improvement of BDB strength evidently, while the sample coated micro-BN exhibits a lower BDB strength than the base resin in any filler loadings investigated.