Hexagonal Boron Nitride as Filler for Silica-Based Elastomer Nanocomposites

Area of Science:

• Materials Science
• Polymer Science
• Nanotechnology

Background:

• Two-dimensional hexagonal boron nitride (hBN) possesses exceptional mechanical, thermal, and insulating properties.
• hBN is explored as a reinforcing filler in elastomer composites to enhance performance.

Purpose of the Study:

• To investigate the effects of pristine (hBN-p) and functionalized (hBN-OH) hexagonal boron nitride on the rheological and mechanical properties of elastomer composites.
• To evaluate hBN as a partial replacement for silica in poly(styrene-co-butadiene) and natural rubber composites.
• To understand the role of hBN functionalization on filler-matrix interactions and composite performance.

Main Methods:

• Exfoliation and ball-milling of hBN to create pristine (hBN-p) and functionalized (hBN-OH) materials.
• Characterization of hBN using FT-IR, TGA, SEM-EDS, WAXD, and HR-TEM to confirm functionalization and structural changes.
• Incorporation of hBN-p and hBN-OH into S-SBR/NR elastomer composites, partially replacing silica.
• Rheological and mechanical testing of composites, including Payne effect, dynamic rigidity, E', hysteresis, and ultimate properties.
• Assessment of composite processability and shelf life using a high-pressure capillary viscometer.

Main Results:

• Functionalization of hBN with -NH and -OH groups (hBN-OH) was confirmed, with reduced layer stacking and increased disorder.
• Partial replacement of silica with hBN (up to 30%) in elastomer composites reduced the Payne effect and increased dynamic rigidity (E' up to 15% at 70 °C).
• hBN-OH composites exhibited improved balance in tan delta and better ultimate properties compared to hBN-p and silica-only composites.
• Both hBN-p and hBN-OH significantly improved composite processability and shelf life, with hBN-OH showing even filler dispersion.
• The functional groups on hBN-OH promoted interactions with silica, coupling agents, and elastomer chains.

Conclusions:

• Hexagonal boron nitride, particularly functionalized hBN-OH, effectively enhances the rheological and mechanical properties of elastomer composites.
• hBN serves as a viable alternative to silica, offering improved processability, shelf life, and filler dispersion in tire compounds.
• The findings suggest that hBN can contribute to developing advanced tire materials with reduced rolling resistance and environmental impact.