Use of Hexagonal Boron Nitride as Reinforcing Agent for Polyamide 11 and the Effect of Surface Treatment with Aminosilane

In this work, the incorporation of hexagonal boron nitride (h-BN) into a polyamide 11 (PA11) matrix was investigated. Composites were prepared by extrusion compounding followed by injection molding, using h-BN contents up to 30 wt.%. To address effects of surface modification, the h-BN surface was modified via thermal hydroxylation at 1000°C followed by grafting with (3-aminopropyl)triethoxysilane (APTES). The materials were characterized using thermogravimetry, calorimetry, electron microscopy, dynamic and tensile mechanical methods, as well as thermal and electron conductivity methods. An adhesion factor analysis revealed inherently poor filler-matrix bonding of h-BN without surface treatment, which promoted a rigid-filler toughening mechanism that enhanced stiffness and flexural properties, particularly at 10 wt.%. At higher filler loadings, thermal conductivity increased by 50% and resistivity increased by up to one order of magnitude. The results also indicated that the composites with APTES-treated h-BN exhibited superior particle/polymer interfacial adhesion. Improvement in flexural and tensile strengths was achieved, surpassing neat PA11. However, APTES modification did not improve thermal or electrical properties, likely because the treatment exfoliated the h-BN particles. These findings underscore APTES treatment's role in optimizing PA11/h-BN biocomposites for high-performance applications while highlighting the need for refined protocols to mitigate h-BN exfoliation-related drawbacks.