Novel hydroxylated boron nitride functionalized p-phenylenediamine-grafted graphene: an excellent filler for enhancing the barrier properties of polyurethane

A hydroxylated boron nitride (BN(OH)_x) functionalized p-phenylenediamine modified reduced graphene oxide (rGO) filler (BN(OH)_x-PrGO) is synthesized for the first time using a facile and novel strategy. BN(OH)_x-PrGO/polyurethane (PU) composite films are prepared using different filler loadings via a solution casting technique. BN(OH)_x-rGO/PU and BN(OH)_x/PU composite films are also prepared in order to compare the reinforcing effects of different fillers. FESEM and TEM analyses show the excellent dispersion and compatibility of BN(OH)_x-PrGO sheets in the PU matrix. The tensile strength and modulus of the composite film show 62% and 95% enhancement, respectively, following the inclusion of 3 wt% BN(OH)_x-PrGO compared to those of the pure PU film. The BN(OH)_x-PrGO/PU composite films exhibit outstanding oxygen gas barrier properties, ideal dielectric properties, and excellent anti-corrosion performances. In particular, the ³BN(OH)_x-PrGO/PU film shows nearly 91% reduction in the O₂ transmission rate compared to the PU film. The permeability of O₂ through the composite film is correlated with the diffusivity, solubility and Bharadwaj model. The dielectric constant (at 10³ Hz) increases from 6.8 for the pure PU film to 13.1 for the ³BN(OH)_x-PrGO/PU composite, and the dielectric loss also remains low for the composite. The potentiodynamic polarization curve shows a substantial shift of the corrosion potential of ³BN(OH)_x-PrGO/PU-coated steel towards the anodic direction compared to the PU film, and it exhibits an ultralow corrosion rate (6.14 × 10⁻⁵ mm per year) and excellent corrosion inhibition efficiency (99.96%) in saline solution.