Highly Thermally Conductive PDMS/h-BN Composites Enabled by Aspect-Ratio-Driven Alignment.

Area of Science:

• Materials Science
• Polymer Composites
• Nanomaterials

Background:

• Hexagonal boron nitride (h-BN) platelets are used in electrically insulating thermal management materials.
• Scalable processing methods for aligning h-BN are crucial for high performance.
• The influence of filler geometry on alignment and thermal transport under shear is not well understood.

Purpose of the Study:

• To investigate how platelet aspect ratio affects the alignment and heat transport in polydimethylsiloxane (PDMS)/h-BN composites.
• To understand the role of filler geometry in shear-induced alignment during processing.

Main Methods:

• Sequential roll-gap controlled two-roll milling was used to process PDMS/h-BN composites.
• A geometric moment-arm perspective was employed to analyze shear-driven rotation.
• Composites with high-aspect-ratio (L-BN) and small (S-BN) platelets were compared.

Main Results:

• High-aspect-ratio L-BN platelets showed more stable flow-parallel alignment compared to S-BN.
• Aligned L-BN composites formed a more interconnected conductive network.
• At 175 wt% loading, aligned L-BN composites achieved a thermal conductivity of 10.3 W m^-1 K^-1, a 94% increase over random counterparts.
• L-BN composites demonstrated superior thermal dissipation and improved stiffness.

Conclusions:

• Platelet aspect ratio is a critical design parameter for achieving efficient alignment in h-BN/polymer composites.
• Optimizing aspect ratio enables enhanced thermal management properties in scalable composite materials.
• This work provides a pathway for designing high-performance, electrically insulating thermal materials.