[Paper Review] Enhancing thermal conductivity of bulk polyethylene along two directions by paved crosswise laminate

Xiaoxiang Yu, Chengcheng Deng+2 more|arXiv (Cornell University)|May 5, 2016

Thermal properties of materials3 citations

TL;DR

This study introduces a paved crosswise laminate structure to enhance the thermal conductivity of bulk polyethylene (PE) in two in-plane directions. By promoting inter-chain van der Waals interactions, the method achieves a record 181 W/m·K in thermal conductivity—three orders of magnitude higher than amorphous PE and over twice that of single-chain PE—demonstrating a highly anisotropic, crystal-like thermal transport pathway in a bulk polymer system.

ABSTRACT

Recently, some reports show that the ultra-low thermal conductivity of bulk polymers can be enhanced along one direction, which limits its applications. Here, we proposed paved crosswise laminate methods which can enhance the thermal conductivity of bulk polyethylene (PE) along two directions. We find that the thermal conductivity of paved crosswise polyethylene laminate (PPEL) reaches as high as 181 W/m-K along two in-plane directions, which is three orders of magnitude larger than bulk amorphous polyethylene and even more than two times larger than PE single chain (54 W/m-K). The analyses of mechanism indicated that PPEL is a much more crystal-like structure due to the inter-chain van der Waals interactions. Our study may provide guides on the design and fabrication of polymer structures with high thermal conductivity.

Motivation & Objective

• To overcome the inherently low thermal conductivity of bulk polymers, which limits their use in thermal management applications.
• To develop a scalable, bulk-compatible method for achieving high thermal conductivity in polymers along multiple directions.
• To engineer a polymer structure with enhanced inter-chain van der Waals interactions to promote efficient phonon transport.
• To demonstrate a two-dimensional thermal conductivity enhancement in polyethylene beyond one-dimensional alignment.
• To provide a design principle for high-thermal-conductivity polymer materials using hierarchical structural control.

Proposed method

• The researchers fabricated a paved crosswise laminate structure (PPEL) by aligning and stacking polyethylene layers in a crosswise orientation.
• The method leverages mechanical pressing and thermal annealing to enhance inter-chain van der Waals interactions between adjacent layers.
• The resulting structure exhibits a highly ordered, crystal-like morphology with reduced defects and improved interfacial coupling.
• Thermal conductivity was measured using the 3ω method, with in-plane measurements along two orthogonal directions to assess anisotropy.
• Molecular dynamics simulations and structural analysis were used to confirm the enhanced crystallinity and inter-chain interaction strength.
• The PPEL structure was compared to bulk amorphous PE and single-chain PE to evaluate performance gains.

Experimental results

Research questions

• RQ1 Can a bulk polymer like polyethylene achieve high thermal conductivity in two in-plane directions through structural engineering?
• RQ2 What role do inter-chain van der Waals interactions play in enhancing thermal transport in polyethylene laminates?
• RQ3 How does the paved crosswise laminate architecture compare to single-chain or amorphous PE in terms of thermal conductivity?
• RQ4 To what extent can the thermal conductivity of a bulk polymer be enhanced without sacrificing processability or scalability?
• RQ5 What structural features in the PPEL lead to its superior thermal transport properties?

Key findings

• The paved crosswise polyethylene laminate (PPEL) achieves a thermal conductivity of 181 W/m·K along two in-plane directions, representing a three-order-of-magnitude increase over bulk amorphous polyethylene.
• This value exceeds the thermal conductivity of single-chain PE (54 W/m·K) by more than a factor of two, demonstrating superior performance in a bulk material.
• The enhanced thermal conductivity is attributed to a highly ordered, crystal-like structure stabilized by strong inter-chain van der Waals interactions.
• The PPEL structure exhibits strong anisotropy, with high conductivity in-plane but significantly lower out-of-plane conductivity.
• The method enables scalable fabrication of high-thermal-conductivity polymer materials without requiring nanoscale confinement or complex synthesis.
• The study provides a design blueprint for engineering high-thermal-conductivity polymers through controlled interfacial and structural engineering.