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Second Thermal and Fluids Engineering  Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

Effects of molecular structure on the thermal and mechanical properties of electrospun vinyl polymer nanofibers




Abstract

Polymers are an important class of materials because of their desirable and tunable properties, abundance and low-cost. The properties of individual polymer nanofibers can be significantly different from those of the corresponding bulk. Thus, it is important to characterize both the microstructure and physical properties of polymer nanofibers to establish the structure-property relations, which could help identify the key factors that dominate the properties and provide guidance to engineering the polymer properties for specific applications. We measured the thermal conductivities and Young’s moduli of three different kinds of vinyl polymer nanofibers, i.e., PVDF, PVA and PVC, fabricated by electrospinning, using the thermal-bridge method and three-point bending method, respectively. These fibers have very similar structures, with only one or two atom differences in each monomer. Importantly, the molecular orientation and crystallinity of individual nanofibers was carefully characterized using polarized micro-Raman spectroscopy. Our results show that in addition to the molecular chain orientation, the molecular composition and structure have important effects on thermal transport properties. Among the measured nanofibers, PVA has the highest thermal conductivity and PVC has the lowest thermal conductivity with those for PVDF in between. We attribute the difference in the measured thermal conductivities to the composition and structure of the monomers. Compared with lighter atoms on the side chains, heavier atoms could significantly alter the vibrational modes to reduce the thermal conductivity. Similarly, the observed Young's modulus of PVA nanofibers is higher than that of PVDF nanofibers, which correlates with the measured thermal conductivity trend.

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