High thermal conductivity through simultaneously aligned polyethylene lamellae and graphene nanoplatelets

Area of Science:

• Materials Science
• Polymer Science
• Nanotechnology

Background:

• Polymer composites often require enhanced thermal conductivity for advanced applications.
• Graphene nanoplatelets (GnP) are promising fillers due to their high intrinsic thermal conductivity.
• Controlling filler and polymer matrix morphology is crucial for optimizing composite properties.

Purpose of the Study:

• To investigate the impact of simultaneous alignment of polyethylene (PE) lamellae and graphene nanoplatelets (GnP) on thermal conductivity (k).
• To quantify the enhancement in thermal conductivity achieved through this simultaneous alignment.
• To correlate the observed property enhancements with structural changes.

Main Methods:

• Preparation of PE-GnP composites with varying GnP content.
• Simultaneous mechanical stretching to align PE lamellae and GnPs.
• Measurement of thermal conductivity (k) using standard techniques.
• Characterization of structural alignment using wide-angle X-ray scattering (WAXS) and polarized Raman spectroscopy.

Main Results:

• A remarkable 1100% increase in thermal conductivity (k) was observed for aligned PE-GnP composites (10 wt% GnP) compared to unoriented pure PE.
• Aligned GnPs were found to be 3 times more effective in enhancing k than randomly oriented GnPs.
• The rate of k increase with applied strain was nearly double in the aligned PE-GnP composite compared to pure PE.
• A high composite k of 5.9 W mK^-1 was achieved at 400% applied strain with 10 wt% GnPs.

Conclusions:

• Simultaneous alignment of PE lamellae and GnPs is a highly effective strategy for significantly enhancing the thermal conductivity of polymer composites.
• This approach offers a pathway to developing advanced materials with superior thermal management capabilities.
• The findings highlight the potential for tailored microstructures to unlock exceptional material performance.