Thermal Conductivity of Electrospun Polyethylene NanofibersQian Zhanga, Jian Maa, Anthony Mayob, Leon Bellana, Richard Mub, and Deyu Lia

aDepartment of Mechanical Engineering, Vanderbilt University, Nashville, TN 37235 bDepartment of Physics, Fisk University, Nashville, TN 37208

IntroductionPolymers are normally thermal insulators. Recent results suggest that the thermal

conductivity of polymeric material is closely related to its microstructure, especially

molecular orientation. Electrospinning can produce well-aligned polymer fiber arrays with

ordered molecular chains within individual nanofibers. However, systematic studies

relating the electrospinning parameters, the resulted fiber structure and associated thermal

conductivity are still lacking.

We report on measurements of the thermal conductivity of electrospun PE nanofibers

prepared under different electric fields to explore the effects of electric field intensity on the

molecular alignment and resulted thermal conductivity. To correlate the relation between

structure and thermal conductivity, we conducted micro-Raman characterization on

individual nanofibers.

Measurement Setup

Fabrication and Measurement

Prepared polyethylene (PE) nanofiber for Raman and

thermal characterization.

Results

Raman spectra of PE powder and PE

nanofibers prepared at different voltages.

Nanofiber shrunk under electron beam irradiation and showed

significant structure change.

Summary

Electrospinning exerts strong elongational force on polymer

chains, resulting in higher degree of molecular orientation and

enhanced level of crystallinity in fabricated nanofibers.

The electrospun fibers show a general trend of higher thermal

conductivity with increasing fabrication voltage. The nanofibers

produced at the same voltage could show significant variation

due to ‘whipping instability’ in the electrospinning process.

We thank the financial support from National Science Foundation (Grant# CMMI-1462866). Jian Ma acknowledges financial support from the National Basic Research Program of China (2011CB707601, 2011CB707605) and the China Scholarship Council (CSC

201306090111). The research is in collaboration with Drs. Yunfei Chen, Zhonghua Ni and Hong Yi.

Thermal conductivity of fibers fabricated at 45 kV and

comparison with high crystalline PE.

Increasing thermal conductivity, chain alignment and

crystallinity with electrospinning voltage.

Acknowledgements

CMMI-1462866

Pt resistors

SiNx beams

SiNx membranes

Microdevice for thermal measurement

Electrospinning fabrication process and illustration of

polymer chains in amorphous and aligned status.