[Paper Review] Thermal conductivity of polymers and polymer nanocomposites

Congliang Huang, Xin Qian+1 more|arXiv (Cornell University)|May 15, 2018

Thermal properties of materials269 references19 citations

TL;DR

This review systematically analyzes thermal transport mechanisms in polymers and polymer nanocomposites at the molecular level, focusing on chain structure, morphology, and inter-chain coupling. It identifies key strategies—such as optimizing filler alignment, interface engineering, and nanostructure design—that enhance thermal conductivity, achieving up to 10-fold improvements in nanocomposites, and outlines future research directions for high-performance thermal management materials.

ABSTRACT

Polymers are widely used in industry and in our daily life because of their diverse functionality, light weight, low cost and excellent chemical stability. However, on some applications such as heat exchangers and electronic packaging, the low thermal conductivity of polymers is one of the major technological barriers. Enhancing the thermal conductivity of polymers is important for these applications and has become a very active research topic over the past two decades. In this review article, we aim to: 1). systematically summarize the molecular level understanding on the thermal transport mechanisms in polymers in terms of polymer morphology, chain structure and inter-chain coupling; 2). highlight the rationales in the recent efforts in enhancing the thermal conductivity of nanostructured polymers and polymer nanocomposites. Finally, we outline the main advances, challenges and outlooks for highly thermal-conductive polymer and polymer nanocomposites.

Motivation & Objective

• To provide a comprehensive understanding of thermal transport mechanisms in polymers at the molecular level.
• To analyze how polymer morphology, chain structure, and inter-chain coupling influence thermal conductivity.
• To evaluate recent advances in enhancing thermal conductivity in nanostructured polymers and polymer nanocomposites.
• To identify key challenges and future research directions for developing high-thermal-conductivity polymer-based materials.

Proposed method

• Systematic review of experimental and theoretical studies on thermal transport in polymers and nanocomposites.
• Analysis of molecular-level factors such as chain alignment, crystallinity, and interfacial phonon scattering.
• Evaluation of nanostructuring techniques including filler dispersion, functionalization, and alignment of nanofillers.
• Use of phonon transport models and interfacial thermal resistance calculations to interpret experimental data.
• Synthesis and comparison of thermal conductivity values across various polymer nanocomposite systems.
• Integration of data from diverse studies to identify trends and design principles for enhanced thermal performance.

Experimental results

Research questions

• RQ1 How do polymer chain structure and morphology affect phonon transport and thermal conductivity?
• RQ2 What is the role of inter-chain coupling and interfacial interactions in thermal transport in polymers?
• RQ3 What are the most effective nanostructuring strategies for enhancing thermal conductivity in polymer nanocomposites?
• RQ4 How do filler type, size, shape, and alignment influence thermal conductivity in nanocomposites?
• RQ5 What are the key limitations and bottlenecks in achieving high thermal conductivity in polymer-based materials?

Key findings

• Thermal conductivity in polymers is strongly influenced by chain alignment and crystallinity, with highly oriented and crystalline regions showing significantly higher conductivity.
• Interfacial thermal resistance between polymer matrices and nanofillers is a major barrier to heat transfer, especially at low filler loadings.
• Strategies such as surface functionalization and controlled filler alignment can reduce interfacial resistance and enhance thermal conductivity by up to 10 times.
• Aligned carbon nanotubes and boron nitride nanosheets show promise, achieving thermal conductivities exceeding 10 W/m·K in optimized nanocomposites.
• Theoretical models indicate that phonon scattering at interfaces and defects limits the maximum achievable thermal conductivity in disordered polymer systems.
• Despite progress, achieving thermal conductivity comparable to metals remains challenging due to intrinsic phonon scattering and low intrinsic conductivity of polymers.