Preparation and characterization of nanocellulose and boron nitride added polymer composites

The rapidly increased thermal load as a result of the continuous down-scaling of electronic devices and increase in power densities require faster and more effective heat dissipation. Therefore, the thermal conductivity of materials has attracted much attention in modern electronics. In this study, the effect of the addition of boron nitride nanosheet (BNNT) and nanocellulose (NC) on the thermal and mechanical properties of the polylactic acid (PLA) matrix was investigated. Boron nitride (BN) is a potential inorganic additive for polymer composites due to its superior thermal conductivity and mechanical properties. Cellulose nanoparticles prepared from microcrystalline cellulose by acid hydrolysis attract attention due to their unique physical and chemical properties and the inherent abundance, renewability and sustainability. In this study, polylactic acid (PLA) composites containing boron nitride and/or nanocellulose in different concentrations were prepared by solvent casting method. Characterization of composites were carried out by using Transmission Electron Microscopy (TEM), Scanning Electron Microscope (SEM) Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Thermal Conductivity, Thermomechanical Analysis (TMA), Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction XRD) analysis and tensile tests. The addition of nanocellulose to the PLA matrix increased the tensile strength and Young's modulus while it decreases elongation at break values. Increased tensile strength with BNNT addition tends to decrease at higher concentrations as a result of BNNT agglomerations. While the thermal conductivity of neat PLA was 0.13 W/mK, with the addition of 5wt. % NC and 5 wt. % BNNT the thermal conductivity reached 0.33 W/mK, after modification of BNNT with vinyltrimethoxy silane, it reached 0.35 W/mK. A large contact surface was obtained between the BNNTs in the matrix and therefore the thermal conductivity value increased by minimizing thermal contact resistance in heat transfer all the way through the composite surface.