Polymer reinforcement using liquid-exfoliated boron nitride nanosheets.

Area of Science:

• Materials Science
• Polymer Science
• Nanotechnology

Background:

• Developing high-performance polymer nanocomposites is crucial for advanced applications.
• Hexagonal boron nitride (h-BN) nanosheets offer potential due to their unique properties.
• Effective dispersion and interfacial interactions are key challenges in nanocomposite fabrication.

Purpose of the Study:

• To exfoliate hexagonal boron nitride (h-BN) into nanosheets.
• To create and characterize polyvinyl alcohol-h-BN nanocomposite films.
• To investigate the mechanical properties and dispersion behavior of these composites.

Main Methods:

• Exfoliation of h-BN via ultrasonication in polyvinyl alcohol (PVA) solution.
• Steric stabilization of h-BN nanosheets by adsorbed PVA chains.
• Centrifugation for size-selection of nanosheets.
• Fabrication of PVA-BN composite films.
• Helium ion microscopy for microstructural analysis.
• Mechanical testing (modulus and strength) at varying h-BN volume fractions.

Main Results:

• Dispersions of h-BN nanosheets with high aspect ratios (∼1400) were achieved.
• Well-dispersed h-BN nanosheets within the PVA matrix were confirmed by microscopy.
• Composite modulus and strength increased linearly with h-BN volume fraction up to 0.1 vol%.
• Exceptional reinforcement rates were observed: dY/dV(f) = 670 GPa and dσ(B)/dV(f) = 47 GPa.
• Maximum property enhancements were limited to ~40% due to the narrow optimal loading range.

Conclusions:

• PVA-BN composites exhibit significant property enhancements at low h-BN loading.
• High interfacial strength between h-BN and PVA was inferred.
• The narrow optimal volume fraction range for property enhancement is a critical limitation.
• This phenomenon mirrors challenges seen in graphene-based composites, hindering widespread high-performance applications.