No abstract

a-crystalline phase poly(vinylidene fluoride) (PVDF) film was oriented uniaxially at different draw ratios. Morphological effects of orientation were investigated by X-ray diffraction and differential scanning calorimetry (DSC) measurements on the oriented samples. The dielectric loss factor was measured from 100 Hz to 1 MHz range between 80 and 400 K as a function of frequency and temperature. While the activation energy of the arelaxation transition was not affected by the orientation, it was observed that there is a linear increase in the activation energy of the b-relaxation transition with draw ratio. The relaxation time of the b-relaxation transition was more affected by the orientation process at lower temperatures.

This article addresses the synthesis and characterization of polyaniline (PANI) both in pure and doped forms with various levels of CuCl 2 and ZnCl 2 in HCl medium where ammonium persulphate was used as an oxidant. Synthesized polymeric materials were characterized spectroscopically (UV-visible spectroscopy, Fourier transform infrared spectroscopy, and Atomic absorption spectroscopy), thermally (Differential scanning calorimetry), and morphologically (Scanning electron microscopy). Free adsorption energy was calculated via Langmuir adsorption isotherm based on the quantities of Cu 2þ and Zn 2þ cations in both pre-and post-polymerization process where it was found that Cu 2þ and Zn 2þ are adsorbed physically on PANI surface. The dielectric measurements as a function of frequency and temperature showed that conductivity decreased with increasing doping levels of metal cations at high temperatures.

No abstract

Morphological characteristics of poly(vinylidene fluoride) (PVDF) films, filled with mass fractions (w ≤ 20%) of Barium Chloride (BaCl2), were investigated by X‐ray diffraction (XRD), Fourier transform infrared (FTIR) absorption spectra and differential scanning calorimetry (DSC) measurements. The dielectric properties of films were measured from 250 Hz to 1 MHz range between 100 and 400 K as a function of frequency and temperature. Spectroscopic data revealed that the filled and unfilled films include α‐, β‐, and γ‐crystalline phases. By a 20% filling, 73% increase was obtained in the total degree of crystallinity. Since the BaCl2 formed fluorine bridges over the chain segments on the crystal lamellar surface, the γ‐crystalline phase decreased, whereas the total degree of crystallinity increased. Dielectric measurements showed that maximum of the dielectric loss factor belonging to β‐relaxation transition decreased linearly with filling level. The filling process did not have any effect on the real dielectric constant till α‐relaxation transition region. However, in the α‐relaxation transition region, it was determined that the real dielectric constant increased linearly with filling level. POLYM. COMPOS., 31:1782–1789, 2010. © 2010 Society of Plastics Engineers.

This article reports synthesis of polypyrrole (PPy) and its composites having various amounts of selenium (Se) in the presence of nitric acid in aqueous medium via chemical oxidative polymerization. Samples were spectroscopically characterized using Fourier transform infrared spectroscopy, ultraviolet‐visible spectroscopy, and atomic absorption spectroscopy. Although morphology of the samples was examined by using scanning electron microscopy (SEM), their thermal properties were studied via differential scanning calorimetry (DSC). The alternating current (ac) conductivity and dielectric properties were investigated as a function of temperature. Variation of adsorption free energy obtained from Langmuir adsorption isotherm showed that metal cations were physically adsorbed onto the polymer surface. SEM images showed that filling process significantly changes the morphology of PPy. DSC results indicated that cold crystallization temperature (Tcc) of unfilled PPy decreases with increasing filling level. Dielectric measurements showed that relaxation times for PPy and its composites have decreased linearly with increasing temperature. The conductivity of the PPy, when filled with 1 g of Se, increased ∼ four times at room temperature for 1 kHz. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

In this study, the effect of measurement temperature and uniaxial drawing on the real (dielectric constant, e 0 ) and imaginary (loss index, e 00 ) parts of the complex dielectric constant of a-crystalline phase poly(vinylidene fluoride) (PVDF) was investigated. The samples having different draw ratios (k) were obtained by drawing the PVDF film at constant speed and temperature. The dielectric measurements were performed in the frequency range of 100 Hz-1 MHz and in the temperature range of 80-400 K. Although e 0 and e 00 were not affected by the orientation process during the b-relaxation transition, it was observed that there were systematical variations for the a-relaxation transition. e 0 and e 00 showed different behaviors depending on the draw ratio at different temperatures. Especially, e 00 was more affected by the orientation process at 380 K.

No abstract