Thermal, Mechanical, and Electric Properties of Exfoliated Graphite Nanoplate Reinforced Poly(vinylidene fluoride) Nanoc
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1129-V11-25
Thermal, Mechanical, and Electric Properties of Exfoliated Graphite Nanoplate Reinforced Poly(vinylidene fluoride) Nanocomposites Fuan He, Jintu Fan* Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China ABSTRACT Poly(vinylidene fluoride) (PVDF)/exfoliated graphite nanoplate (xGnP) nanocomposites were prepared by a solution mixing method for the first time. The thermal, mechanical and electric properties of these nanocomposites were studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and an impedance analyzer, respectively. The DSC results indicated that xGnP might act as the nucleating agents and accelerated the overall non-isothermal crystallization process of PVDF. Meanwhile, the incorporation of xGnP also significantly improved the storage modulus and conductivity of the PVDF/xGnP nanocomposites with an increment in the graphite nanoplate content, respectively. INTRODUCTION Exfoliated graphite nanoplate (xGnP) has good electrical and thermal conductivity, high mechanical strength, and large aspect ratio [1]. Because of these outstanding features, xGnP has been considered as a promising reinforced agent for the preparation of polymeric nanocomposites [2-8]. Poly (vinylidene fluoride) (PVDF) has received considerable attention because of its good mechanical properties, resistance to chemicals, high dielectric permittivity, and unique pyroelectric and piezoelectric properties [9,10]. In the present work, we attempt to develop new nanocomposites consisting of poly(vinylidene fluoride) (PVDF) and exfoliated graphite nanoplates (xGnPs) by solution mixing method. The effect of different concentrations of graphite nanoplates on the non-isothermal crystallization behavior, dynamic mechanical properties, and conductivity of PVDF/xGNP nanocomposites was investigated. EXPERIMENT xGnPs were obtained from subjecting natural graphite flake to acidic intercalation, rapid thermal treatment, and ultrasonic powdering in sequence (see Figure 1). The PVDF/xGnP nanocomposites were prepared by mixing desired amount of xGnP and PVDF in 100 ml of DMF solution at 80 oC under stirring for 2h and then treated with ultrasonic powdering for another 2h. The resultant products were dried at 70 oC for 3 days. DSC thermal analysis was carried out with a Perkin Elmer DSC-7 differential scanning calorimeter calibrated under a nitrogen atmosphere. Dynamic mechanical property was measured by a Perkin Elmer diamond DMA lab system at a frequency of 1 Hz in a nitrogen atmosphere, with a temperature range from −80 to 80 oC at a scan rate of 5 oC /min. Conductivity of the samples were measured using an Agilent 4294 A impedance analyzer in the frequency range of 50-107 Hz at room temperature.
DISCUSSION Figure 1(b) presents the SEM image of xGnPs, the obtained graphite nanoplates have a size of 20–60 nm in thickness and 0.5–25 µm in diameter. According to the FTIR results reported by other groups [1, 4], there are some functional groups, such as C–O–C
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