Synthesis of novel functionalized and exfoliated hexagonal boron nitrides filler and their compatibilization chemistry for high-performance biocomposites

Abstract

Currently, high-performance polymer composites are used in a wide range of demanding applications, however, they are mainly derived from oil-based polymers and multifunctional fillers. But as the demand for more sustainable alternatives to conventional oil-based plastics increases, so does interest in utilizing biopolymers as alternatives in packaging and other industrial applications due to their outstanding ecofriendly functionalities. However, biopolymers generally lack required characteristics needed for high performance demanding applications. These insufficiencies can be countered by creating composites using multifunctional nanofillers such as boron nitride nanosheets (BNNS) compatible with biopolymers. However, nanofillers commonly require functionalization to be compatible with biopolymers, and common functionalization methods discussed in the literature are difficult to scale to large amounts needed for polymer composite applications or need hazardous reagents or extreme conditions.

The main aims of this thesis were to produce BNNS-based multifunctional nanofiller in large quantities through simple, high-yield, and green methods; and studies of their compatibility with biopolymers to produce multifunctional biocomposite in diverse applications, such as UV-shielding polymeric materials, wood adhesives, and packaging film. For this thesis, hexagonal boron nitride (h-BN) was functionalized using maleic anhydride through a simple thermal driven Diels-Alder cycloaddition reaction, and the resulting multifunctional maleic acid functionalized boron nitride nanosheet (BNNSMA) nanofiller was used to fabricate biocomposites with nanofibrillated cellulose (NFC), sodium alginate (Na-alginate), and cellulose acetate butyrate (CABU) using solution removal method.

The BNNS-MA was successfully integrated into all biopolymers utilized in this thesis, and the nanofiller significantly improved mechanical, UV-shielding, and antioxidant properties at low loadings. The improvements were found to be dependent on how homogenously the nanofiller was dispersed in the solution as well as in biopolymer matrix.

The results of this study show possibility of synthesizing multifunctional BNNS nanofillers with high-yield for the fabrication of biocomposites with enhanced multifunctionalities.