Relaxation map analysis

In the work described here, TSC spectroscopy experiments have been performed using a TSC and Relaxation Map Analysis (RMA) dielectric spectrometer developed in our laboratory and available from Settaram. The TSC cell is shown in Figure 11.3. Powdered compounds (some tens of milligrams) were compressed into flat disks of 0.8-cm diameter and approximately 1 mm thick. The sample was placed between stainless steel disks, which ensures electrical contact, thus allowing polarization and current measurement. The maximum applied voltage was 500 V, with an accuracy of 0.1 V. The depolarization current was recorded using a very... 

Solomat Instrumentation X TSC/RMA Spectrometer Thermally Stimulated Current Depolarization/ Relaxation Map Analysis... 

Cambridge University Press, Cambridge. A related technique, that of thermally stimulated current analysis is described by Ibar IP (1993) Fundamentals of Thermal Stimulated Current and Relaxation Map Analysis. SLP Press, New Canaan. 

Relaxation-map analysis (RMA) n. A technique used on the results of a series of thermally stimulated current experiments in which the TSC data are transformed into relaxation times and plotted versus reciprocal absolute temperature to estimate enthalpy and entropy of activation for the molecular relaxations. 

The molecular dynamics of similar chemical structure blends of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN) were investigated using the TSDC technique [74]. Transesterification reactions between the neat components developed during the melt-mixing process. When the a-relaxation processes of the reactive blends were analyzed into their elementary modes by means of relaxation map analysis, the activation energies of the a-relaxation process were found not to be significantly affected by the transesterification reaction. However, the polarizability of the blend was considerably decreased as the PEN content increased, due mainly to the increased stiffness of the polymer backbone. 

A review is presented of the techniques involved in the thermal analysis of polymers. Techniques discussed include differential scanning calorimetry, differential photocalorimetry, thermogravimetric analysis, thermomechanical analysis, dynamic mechanical analysis, dielectric, thermally stimulated current/relaxation map analysis analysis, and thermal conductivity analysis. 381 refs. 

A significant increase in the precision of TSC was achieved when Lacabanne [113] developed the method of windowing polarisation, and this in turn enables the process known as relaxation map analysis to be applied to polymer systems [114, 115]. This also enables fine detail within a polymer to be elucidated and a thorough description of the technique and its capabilities has been provided by Ibar [116]. 

Ibar JP. Fundamentals of Thermally Stimulated Current and Relaxation Map Analysis. New York SLP Press, 1993. 

In a similar fashion. Thermally Stimulated Current spectrometry (TSC) makes use of an appHed d-c potential that acts as the stress to orient dipoles. The temperature is then lowered to trap these dipoles, and small electrical currents are measured during heating as the dipoles relax. The resulting relaxation maps have been related to G and G" curves obtained by dynamic mechanical analysis (244—246). This technique, long carried out only in laboratory-built instmments, is available as a commercial TSC spectrometer from Thermold Partners L.P., formerly Solomat Instmments (247). 

Several recent papers coiqpare the two types of analysis (32-34) (see also the paper herein by Tran and Brady). Brant and Christ coiqpare the abilities of the two approaches to predict experimental behavior in their chapter herein. Two strategies for constructing relaxed maps are discussed in the chapters by Tran and Brady and by French, Tran and P6rez. 

Clearly by working with typical spatial resolutions of approximately 30-50 pm, individual pores within the material are not resolved. However, a wealth of information can be obtained even at this lower resolution (53,54,55). Typical data are shown in Fig. 20, which includes images or maps of spin density, nuclear spin-lattice relaxation time (Ti), and self-diffusivity of water within a porous catalyst support pellet. In-plane spatial resolution is 45 pm x 45 pm, and the image slice thickness is 0.3 mm. The spin-density map is a quantitative measure of the amount of water present within the porous pellet (i.e., it is a spatially resolved map of void volume). Estimates of overall pellet void volume obtained from the MR data agree to within 5% with those obtained by gravimetric analysis. 

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