Exfoliation Of Hexagonal Boron Nitride And Its Application In Polymer Composites

H-BNNSs is widely applied in various fields due to its excellent physical and chemical characteristics such as high chemical inertness and thermal stability.However,the electronegativity difference between N atoms and B atoms of boron nitride begets a lip-lip interaction with the B-N bonds generating.Nevertheless,van der Waals force makes a stronger interlayer force of hexagonal boron nitride(h-BN),which increases the difficulties of exfoliating h-BN and hinders the application of h-BNNSs.As a consequence,the efficient exfoliating of h-BN and the dispersion stability in a solvent are studied here to promote the performance of h-BNNSs.Here,we propose to use ethyl cellulose(EC)and cationic ethyl cellulose(CEC)as surfactants which assist the h-BN to exfoliate and prepare BN/EC and BN/CEC for improving the chemical stabilities and resistance of waterborne polymer coatings.Based on water-based acrylic-alkyd emulsion and water-based epoxy resin,boron nitride/acrylic-alkyd composite(WAAR/BN)and boron nitride/epoxy composite(WEP/BN)were constructed.The following details:(1)The h-BN was exfoliated by a cell pulverization ultrasonic apparatus using a liquid exfoliating method.We propose to use EC and CEC as surfactants and NMP as the solvent to exfoliate h-BN into BN/EC and BN/CEC.The effects of different surfactants,surfactant dosage,and the ultrasonic duration of pulverization on the exfoliating effect and properties of h-BNNSs were investigated.Finally,the optimal preparation scheme was determined:the mass ratio of h-BN to EC was 20:2 while the cell crushing ultrasound time was 8 h;the mass ratio of h-BN to CEC was 20:2,and the cell crushing ultrasound time was 8 h.(2)Raman and XRD spectra were performed to characterize changes in the exfoliation degree and interlayer spacing of the h-BNNSs.The changes in the morphology of boron nitride before and after exfoliating were observed using TEM and SEM tests.The dispersion and stability of the boron nitride nanosheets obtained under the optimal exfoliating conditions in different solvents were compared with the TSI test.(3)EBN and CBN were used as nano-fillers to dope into the aqueous acrylic-alkyd emulsion prepared by the reverse conversion emulsification method to construct WAAR/EBN and WAAR/CBN composite.Explore the effects of properties of composite with different amounts of EBN and CBN doping with,and determine the optimal doping amount of EBN and CBN.Water absorption,contact angle,TGA-DTG,thermal conductivity,SEM,EIS,and salt spray tests were used to investigate the effects of EBN and CBN doping amount on the water resistance,surface topography,thermal,mechanical and anti-corrosive properties of composites.It shows that when the doping amount of EBN and CBN is 6.0 wt%,the properties of WAAR/BN composites reach the best.(4)The WEP/EBN and WEP/CBN composite were constructed by doping EBN and CBN as nano-fillers into the aqueous epoxy emulsion using the inverse emulsion method.Explore the effects with properties of composite with different amounts of EBN and CBN doping,and the optimal doping amount of EBN and CBN was determined.Water absorption,contact angle,TGA-DTG,thermal conductivity,SEM,EIS,and salt spray tests were used to explore the effects of EBN and CBN doping on the water resistance,surface topography,thermal,mechanical and anti-corrosive properties of composites.The results show that when the doping amount of EBN and CBN is 6.0 wt%,the properties of WEP/BN composites reach the best.By comprehensively comparing the properties,we can find that the performance of the WAAR/CBN and WEP/CBN composite samples obtained with CBN doping is better than that of the WAAR/EBN and WEP/EBN composite samples obtained with EBN doping,and When the doping amount is 6.0 wt%,the performance in the same series is better.