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5/17/2017  |   11:25 AM - 11:50 AM   |  2

Very high thermal conductivity of heat-stretched polyethylene microfiber

This presentation reports a significantly enhanced thermal conductivity of ultra-high molecular weight polyethylene (UHMW-PE) microfiber by stretching at controlled speed and temperature. A remarkable improvement from 21 W/m?K to 51 W/m?K is achieved with a relative low elongation ratio ~ 6.7. It represents the first time highly thermal conductive polymer obtained at the engineering level. The mechanism of the improvement is uncovered by phonon scattering model calculation, X-ray diffraction (XRD) analysis and Raman spectroscopy. The calculated domain size increases from 6.33 nm to 17.88 nm, confirming elongated phonon life time and explaining the enhanced thermal transport. XRD pattern shows no obvious change of crystallite size and orientation while the crystallinity decreases from 92% to 83% after stretching. Polarized Raman spectra indicate that heat stretching could enhance the alignment of molecular chains in the amorphous region. Based on the structural characterization, a physics model is proposed to explain the contradiction between decreased crystallinity and enhanced thermal conductivity.

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Bowen Zhu (POC,Primary Presenter), Iowa State University,;
Xinwei Wang (Co-Author), Iowa State University, ;

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