Dielectric relaxations in PEEK by combined dynamic dielectric spectroscopy and thermally stimulated current

Abstract

The molecular dynamics of a quenched poly (ether ether ketone) (PEEK) was studied over a broad frequency range from 10-3 to 10 6 Hz by combining dynamic dielectric spectroscopy (DDS) and thermo-stimulated current (TSC) analysis. The dielectric relaxation losses e 00 KK has been determined from the real part e 0 T(x) thanks to Kramers-Kronig transform. In this way, conduction and relaxation processes can be analyzed independently. Two secondary dipolar relaxations, the c and the b modes, corresponding to non-cooperative localized molecular mobility have been pointed out. The main a relaxation appeared close to the glass transition temperature as determined by DSC; it has been attributed to the delocalized cooperative mobility of the free amorphous phase. The relaxation times of dielectric relaxations determined with TSC at low frequency converge with relaxation times extracted from DDS at high frequency. This correlation emphasized continuity of mobility kinetics between vitreous and liquid state. The dielectric spectroscopy exhibits the a c relaxation, near 443 K, which has been associated with the rigid amorphous phase confined by crystallites. This present experiment demonstrates coherence of the dynamics of the PEEK heterogeneous amorphous phase between glassy and liquid state and significantly improve the knowledge of molecular/dynamic structure relationships.

Broadband dielectric spectroscopy of Nafion‐117, sulfonated polysulfone (sPSF) and sulfonated polyether ketone (sPEK) membranes

“…Leonardi et al . reported an E A of 56 kJ mol −1 to a relaxation appearing in PEEK polymer; they attributed this relaxation to the phenyl ring rotation between the ether linkages . In the similar temperature range, the peak observed with sPEK also shifts through the entire frequency range and has an E A of 44.62 kJ mol −1 (Supporting Information Table S1).…”

Dielectric characterization of high-performance spaceflight materials

“…Based on literature results, the relaxation around 400 kHz is likely the β-relaxation and the lower frequency relaxation is like due to Maxwell-Wagner-Sillars (MWS) effects [12]. A small amount of low frequency conductivity was measured within the samples, which increased slightly as the frequency decreased below 1 Hz.…”

“…Maxwell-Wagner-Sillars (MWS) effects are observed within this frequency range (γ in Figure 5), which is an interfacial relaxation present in heterogeneous materials when subjected to an electric field [9,10,11,12]. These heterogeneous sites include amorphous/crystalline regions, impurities or chemicals remaining from processing (i.e plasticizers or catalysts) whose permittivity or conductivity values are different from those of the main phase [10].…”

“…At high frequency, below the glass-transition temperature (143 °C [7]), a broad relaxation occurs which is characterized by the localized non-cooperative motions of the chain fragments, primarily the resonance of the aromatic rings [12]. This process is the β-relaxation and is associated with the initial movement of the glass-transition relaxation (α) which occurs above 143 °C [9].…”

“…The β-relaxation is characterized by the localized non-cooperative motions of the chain fragments, primarily the rotation of the aromatic rings [12]. These two relaxations were observed to have their characteristic relaxation frequency decrease with increased accelerated weathering and thermal aging.…”