Selective Distribution of Filler in PMMA/PLA/BN Thermally Conductive Composites: Theoretical Prediction and Experimental Investigation

In this study, poly(methyl methacrylate) (PMMA)/polylactic acid (PLA)/boron nitride (BN) composites were fabricated by melt blending and solution blending, respectively. When the content of BN achieved 20%, the thermal conductivities of both in-plane and out-of-plane were found to increase considerably by 303 and 334%, respectively. Scanning electron microscopy (SEM) observations substantiated that a thermal conduction path could be in situ established at a filler content of 20% in the composites prepared by solution blending, which was earlier than that established in the composites prepared by melt blending. Analysis based on the results of both transmission electron microscopy (TEM) and SEM after a selective etching of the composites proved that BN was selectively distributed in the PLA phase, making it possible to prepare composites with greatly enhanced thermal conductivity (TC) via altering the mixing order of preparing the route. More importantly, our findings suggested that there exists a direct scaling between mechanical properties and TC, which could clearly be expressed by a linear master curve. The present work will provide insight into the industrial manufacturing of PMMA/PLA/BN composites, which could be potentially applicable in electronic devices, e.g., 2.4G/5G routers, notebook keyboards, etc.