Enhanced Polyaspartate Polyurea Reinforced with Boron Nitride Nanosheets for Protective Coatings

The current study explores the advancements in mechanical and functional properties of polyaspartate polyurea (PAPU) for protective coating applications upon addition of boron nitride nanosheets (BNs).The mechanochemical approach was employed to synthesize BNs of thickness 3.32 nm, followed by successful chemical modification with m-xylylenediamine using microball milling. PAPU nanocomposites based on pristine BNs and modified BNs (m-BNs) were prepared and systematically investigated, showing exceptional mechanical properties and environmental reliability. Only 0.1 wt % of m-BNs increased the tensile strength, Young’s modulus, and elongation at break of PAPU by 56.7%, 41%, and 67.4%, respectively. Although Young’s modulus of polyurea continued to increase after 0.1 wt % m-BN, other properties start to drop due to aggregation. The impact strength of the aluminum substrate was increased by 22.2% after coating with 0.1 wt % PAPU/m-BNs nanocomposite, highlighting its suitability for metal protection. Furthermore, comprehensive environmental reliability tests demonstrated PAPU nanocomposites’ efficacy as robust protective coatings even after prolonged exposure to diverse chemical conditions. For example, the impact strength of neat PAPU and PAPU/m-BN composite, respectively, reduced by 25% and 9.9% after the salt-fog test. The study highlighted the importance of adding a reinforcing phase and chemical modification in PAPU nanocomposites in order to achieve high mechanical performance and multifunctional protective coatings.