Dielectric Studies Of Polyester/Polycarbonate Blends

1989 ◽  
Vol 171 ◽  
Author(s):  
James K. O'Reilly ◽  
Joseph S. Sedita
Keyword(s):  
Free Volume ◽  
Relaxation Times ◽  
Concentration Fluctuations ◽  
Dielectric Studies ◽  
Enthalpic Relaxation ◽  
Wlf Equation

ABSTRACTDielectric and enthalpic relaxation times have been measured as a function of composition and temperature. A fractional exponential (W–W) distribution of relaxation times fits both the dielectric and enthalpic relaxation times with different values which are a function of composition. Free volume parameters calculated using the WLF equation are not simple functions of the composition. Concentration fluctuations are considered to be important in these phenomena.

Dielectric Studies of 4-w-Hexyloxy-4’-Cyanobiphenyl (60CB) at Elevated Pressure

1999 ◽  
Vol 54 (6-7) ◽  
pp. 365-369 ◽  
Author(s):  
S. Urban ◽  
M. Smoluchowski
Keyword(s):  
Dielectric Permittivity ◽  
Order Parameter ◽  
Nematic Phase ◽  
Activation Volume ◽  
Activation Enthalpy ◽  
Ambient Pressure ◽  
Relaxation Times ◽  
Elevated Pressure ◽  
Dielectric Anisotropy ◽  
Dielectric Studies

Abstract The principal dielectric permittivity components in the nematic phase of 4-rc-hexyloxy-4’-cyanobiph-enyl (60CB) were measured as functions of temperature at ambient pressure and as functions of pres-sure up to 100 MPa at several constant temperatures. The dielectric anisotropy is analized in the frame of the Maier-Meier equations. The pressure dependence of the order parameter is deduced. Preliminary results for the activation volume and activation enthalpy from the pressure and temperature dependenc-es of the longitudinal relaxation times are obtained.

Thermo-Mechanical Investigation of Free Volume Theory for Polyamie-6

2016 ◽  
Vol 819 ◽  
pp. 580-584
Author(s):  
Jamal Umer ◽  
Ivan Saprounov ◽  
Igor Emri ◽  
Barbara Zupančič ◽  
Muhammad Wakil Shahzad
Keyword(s):  
Mechanical Properties ◽  
Free Volume ◽  
Polyamide 6 ◽  
Time Dependent ◽  
Effect Of Temperature ◽  
Free Volume Theory ◽  
Wlf Equation ◽  
Mechanical Investigation ◽  
Temperature And Pressure

Polymers always show time-dependent mechanical properties. In order to use polymers in engineering applications, long-term mechanical propertes should be characterized. Free volume theroy is the mostly used theory to predict and model the mechanical properties of polymers. The effect of temperature is modelled thorugh William-Landel-Ferry (WLF) equation, whereas, the combined effect of temperature and pressure is modelled by Filler-Moonan-Tschoegl (FMT) equation. Both of the models are based on free volume theory. A set of expermentations were performed to investigate the validity of free volume concpet for one of the most important engineering polymer; i.e. Polyamide-6.

Rotational Diffusion of Chromophores Inside a Glassy Polymeric Film Studied By Electrooptical Interferometry

1989 ◽  
Vol 173 ◽  
Author(s):  
R. Meyrueix ◽  
G. Mignani
Keyword(s):  
Free Volume ◽  
Broad Spectrum ◽  
Oblique Incidence ◽  
Rotational Diffusion ◽  
Relaxation Times ◽  
Secondary Transition ◽  
Short Term ◽  
Dipole Interactions ◽  
Different Temperatures

ABSTRACTPerot Fabry interferometry under oblique incidence provides a powerful tool for the determination of the complex values of the independant components of the tensors χ2(−ω;ω,ο) and χ3(−ω;ω,ο,ο) of poled films. Deorientation of Disperse Red One chromophore in a poled film can be followed by the decrease with time of two order parameters. In the short term regime, the relaxation times of this process are spread over a broad spectrum. By comparing the chromophore dynamics in PMMA, PS and SAN at different temperatures, it appears that free volume and secondary transition concepts cannot fully explain the chromophore behavior. Chromophore dipole/Polymer dipole interactions are invoked in order to explain the slow deorientation rate in SAN.

An Application of a Free Volume Model to Lubricant Rheology 2—Variation in Viscosity of Binary Blended Lubricants

1984 ◽  
Vol 106 (2) ◽  
pp. 304-311 ◽  
Author(s):  
S. Yasutomi ◽  
S. Bair ◽  
W. O. Winer
Keyword(s):  
High Pressure ◽  
Binary Mixture ◽  
Free Volume ◽  
Mineral Oil ◽  
Practical Applications ◽  
Polyphenyl Ether ◽  
Volume Model ◽  
Wlf Equation ◽  
Free Volume Model ◽  
Lubricant Rheology

The modified WLF equation developed in Part 1 was applied to the variation in viscosity, μ(T,P), for two series of binary blended lubricants containing a common synthetic diester (di(2ethylhexyl)sebacate) in a polyphenyl ether (5P4E) and in a naphthenic mineral oil (N1). Dilatometric observations and the viscosity analysis indicate that the relations needed to predict the pressure functions in the modified WLF equation for the binary mixture can be obtained from those of respective components. These relations allow us to estimate μ(T,P) of a binary blended lubricant without measurements of the high pressure viscosity of the blend. For practical applications, the modified WLF equation may also be useful for predicting μ(T,P) of blended lubricant products.

COOPERATIVE FREE VOLUME RATE MODEL APPLIED TO THE PRESSURE-DEPENDENT SEGMENTAL DYNAMICS OF NATURAL RUBBER AND POLYUREA

2019 ◽  
Vol 92 (4) ◽  
pp. 612-624
Author(s):  
Ronald P. White ◽  
Jane E. G. Lipson
Keyword(s):  
Natural Rubber ◽  
Free Volume ◽  
Relaxation Times ◽  
Close Packing ◽  
Rate Model ◽  
Segmental Dynamics ◽  
Glass Forming ◽  
Segmental Relaxation ◽  
The Difference ◽  
New Applications

ABSTRACT We apply the cooperative free volume (CFV) rate model for pressure-dependent dynamics of glass-forming liquids and polymer melts, focusing on two new applications of the model, to natural rubber and to polyurea. In CFV, segmental relaxation times, τ, are analyzed as a function of temperature (T) and free volume (Vfree), where the latter provides an insightful route to expressing dynamics relative to using the system's overall total volume (V). Vfree is defined as the difference between the total volume and the volume at close packing and is predicted independently of the dynamics for any temperature and pressure using the locally correlated lattice equation-of-state analysis of characteristic thermodynamic data. The new results for natural rubber and polyurea are discussed in the context of results on a set of polymeric and small-molecule glass formers that had previously been modeled with CFV. We also discuss the results in the context of recent connections that we have made with the density-scaling approach.

Dielectric Studies of Smectogenic Members of the 4’-alkyl-4-cyanobiphenyl (nCB) Homologous Series

2004 ◽  
Vol 59 (6) ◽  
pp. 316-324 ◽  
Author(s):  
Joanna Czub ◽  
Urszula Gubernat ◽  
Bo Gestblom ◽  
Roman Da̡browski ◽  
Stanisław Urban
Keyword(s):  
Homologous Series ◽  
High Frequency ◽  
Relaxation Times ◽  
Low Frequency ◽  
Activation Entropy ◽  
Viscosity Data ◽  
Dielectric Studies ◽  
Smectic A ◽  
Relaxation Measurements ◽  
Molecular Rotations

Results of dielectric studies of smectogenic members of the nCB (4’-alkyl-4-cyanobiphenyl, n = 9÷12) homologous series are presented. The dielectric relaxation measurements were performed in the isotropic (Is) and smectic A (SA) phases. The relaxation times characterizing the molecular rotations around the short axes (the low frequency, l. f., process) were established for both phases. In the Is phase the high frequency process connected with the molecular rotations around the long axes was also determined. The l. f. relaxation times were analysed using the Arrhenius and Bauer activation equations, which yielded the activation enthalpy ΔH and activation entropy ΔS. All results were analysed together with the literature data on the shorter members of the homologous series as well as on 14CB recently published. The ΔH and ΔS values show typical odd-even alternation that is especially well seen for the shorter members. In the Is phase the l. f. relaxation times are related to the viscosity data measured recently by Jadzyn et al.

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