Crystalinity Properties of Carbon Nanotube-Polyvinylidene Fluoride Composites
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Crystalinity Properties of Carbon Nanotube-Polyvinylidene Fluoride Composites Xiaobing Shan, Peixuan Wu, Lin Zhang and Z.-Y Cheng Materials Research and Education Center, Auburn University, Auburn, AL 36849 ABSTRACT Single-wall and multi-wall carbon nanotube blends (0 to 0.5 vol% ) with polyvinylidene fluoride (PVDF) have been prepared using solution cast method and characterized. By acid treatment, it has been observed that nanotube has been well functionalized and uniformly dispersed into the polymer. X-ray diffraction analysis coupled with differential scanning calorimetry (DSC) has revealed that carbon nanotube alters the crystallinity of PVDF and thereby enhances the β-phase in PVDF. Experimental results have demonstrated that enhancement of β-phase is a function of carbon nanotube concentration. INTRODUCTION It is well known that due to its novel structural, electronic, and mechanical properties, carbon nanotube has been applied in many fields, such as carbon nanotube composites. Incorporation of carbon nanotube into the organic polymers enables the fabrication of new high performance hybrid materials with good electrical and thermal transport properties [1-3]. A significant increase in thermal conductivity of organic fluid and polymers with relative low concentration of carbon nanotubes has been reported [4-7]. Poly(vinylidene fluoride) (PVDF) has attracted much attention because of its widely applications to high pyroelectric, piezoelectric, and ferroelectric materials. It is known that PVDF exhibit four crystalline phases, namely α, β, γ and δ phases [8]. In those phases, β-phase is especially interest due to its large pyro and piezoelectric effect. Currently, the mainly interest is focused on β-phase PVDF [9-10]. Comparing with P(VDF-TrFE), PVDF homopolymer contains more dipoles in its molecular structure and is at much lower cost. However, α-phase is thermodynamically more stable in PVDF than β-phase. The influence of CNTs on α –β phase transition in PVDF has been investigated by adjusting the CNTs concentration and processing parameters. In this paper, carbon nanotube- Poly(vinylidene fluoride) composites are fabricated and we investigate functionalized carbon nanotubes/ Poly(vinylidene fluoride) (SWNT or MWNT/PVDF) composites with low concentrations of SWNT or MWNT (0 to 0.5 vol%). X-ray diffraction analysis and DSC has been used to study its properties, such as crystallinity, at different annealing temperatures. EXPERIMENTAL The carbon nanotube (SWNT or MWNT) were obtained from a commercial source (Shenzhen Nanotech Port Co. Ltd., China). A commercial SOLEF 1010 Poly(vinylidene fluoride) was supplied from Solvay Solexis, Inc. The carbon nanotube-polymer composite were prepared by traditional casting method and hot pressing techniques. The carbon nanotube was functionalized before mixed with PVDF. The functionalized procedure is shown as following:
1. 3:1 Concentrated H2SO4: HNO3 mixture was chosen for the oxidizing acid in the cutting operation. 2. After weighting the CNT, Stirring the
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