Effect of tacticity on the dielectric properties of polystyrene

Abstract

Dielectric properties of polystyrene (PS) were investigated by measuring electrical conduction current and frequency spectra of complex permittivity at temperatures from 20 to 199 °C. To clarify the effects of tacticity, the properties were compared among two kinds of syndiotactic PS (SPS) with different crystallinity values and one atactic PS (APS). Experimental results indicate that the two SPS samples show a high melting point of about 250 °C. The conductivity is lowest in SPS with the low crystallinity in the whole temperature range from 20 to 199 °C, while APS had a breakdown at 140 °C. Moreover, the low‐crystallinity SPS shows the smallest permittivity values and the smallest increase in dielectric loss factor toward low frequencies among the three samples. The high‐crystallinity SPS has α crystals. Since the density of α crystals is lower than the amorphous region, the charge transport and polarization are easier in the high‐crystallinity SPS than in the low‐crystallinity SPS. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Dielectric spectroscopy of nanocomposites based on iPP and aPS treated in the water solutions of alkali metal salts

“…Relative dielectric constant ( ε′ ) was measured in the frequency range from 20 Hz to 9 MHz at a relative humidity of 35%, normal atmospheric pressure, and temperature of 22°C. The measured values of ε′ for untreated samples corresponded with the literature data for iPP and aPS . Frequency dependence of ε′ for iPP and aPS were very steady since they belong to nonpolar polymers.…”

“…Pillai and Rashmi have submitted evidence that permittivity is independent of frequency within the range of investigations (310 to 9600 Hz). Also, Hikosaka and Ohki have measured frequency dependence of relative permittivity ( ε ′) and noticed small changes of ε ′ in a frequency range from 10 −2 to 10 5 Hz of about 1,5%.…”

Complex Permittivity Spectra of Various Insulating Polymers at Ultrawide‐Band Frequencies

“…Various properties of each polymer [1][2][3][4][5][6] Sample ε r ʹ @ 500 Hz 33 GHz to 110 GHz, 1.5 THz to 4.0 THz) were measured using different instruments. First, using Solartron SI126096W impedance analyzer, we applied ac voltage with effective value of 3 V to a 4 cm × 4 cm samples with aluminum foil (diameter: 2 cm) fixed at the middle on both sides, measured the electrostatic capacitance and the dielectric loss tangent (tanδ) at 10 mHz to 1.0 MHz by varying temperature from room temperature to 200°C at an increment of 20°C, and calculated ε r ′ and ε r ′′ .…”

Space charges remaining in polymers after electron beam irradiation and the role of conductivity in their decay profiles

“…Further, it is reasonable to assume that τ 1 satisfies the relation where ɛ , ρ , and σ are the permittivity, resistivity, and conductivity of each polymer, respectively. Using the relative permittivity values as 2.2 for LP, 3.4 for PT, 2.7 for SP, and 2.9 for PN , σ of each polymer was calculated from the respective τ 1 values. The σ values calculated by this procedure are shown by inverted closed triangles (▼) in Fig.…”