Structure-Rheology-Property relationships in double-percolated Polypropylene/Poly(methyl methacrylate)/Boron nitride polymer composites

Double-percolated thermally conductive polymer composites comprising of polypropylene (PP), poly (methyl methacrylate) (PMMA), and boron nitride (BN) were successfully produced by melt compounding. The effects of BN platelets sizes on morphology and thermal conductivity (TC) were investigated by mixing three different sizes BN, namely 16, 30 and 180 μm with PP and PMMA. The obtained results demonstrate that for all the sizes, BN platelets were either in the PMMA phase or at the interface, and the ternary composites with high filler loadings showed enhanced TC compared to the corresponding binary systems. It is shown that smaller BN platelets led to finer morphology, which caused more interfaces and consequently more phonon scattering and lower TC of the system. Finally, we show for the first time that there is a direct scaling between particle size, mechanical properties and TC. This work proved the advantage of using double-percolated structure to improve TC of polymer composites and provided a better understanding of the filler size effects on the morphology and TC of ternary systems.