Calorimetric glass transition temperature

The temperature range of T5 to Ti is referred as the glass transition region. The calorimetric glass transition temperature (Tg) may be defined as the temperature... 

Table 4 Melting Point (Tm), Critical Temperature (Tc), and Calorimetric Glass Transition Temperature (Tg) of the Alcohols and Polymers Selected...

Abstract Thin polystyrene films are prepared by spin-coating and annealed above the calorimetric glass transition temperature Tg alternatively in vacuum, in a pure nitrogen atmosphere, in the presence of water vapor or in ambient air. 

Bohmer and coworkers " used spin-lattice relaxation weighted stimulated-echo spectroscopy to find evidence for a correlation of the a- and the JG P-relaxation times above the calorimetric glass transition temperature of ortho-terphenyl, D-sorbitol, and cresolphthaleindimethylether (CDE or KDE). They found that the cr-relaxation can be modified by suppressing the contributions of some subensembles of the JG p-relaxation in these glassformers. An earlier deuteron NMR experiment also gave indication of a possible correlation of the a- and JG p-relaxations of polystyrene. ... 

Koh YP, McKeima GB, Simon SL (2006) Calorimetric glass transition temperature and absolute heat capacity of polystyrene ultrathin films. J Polym Sci, Part B Polym Phys... 

Here ar is a shift factor (a = Thn/Treference)- If for l/rreference the relaxation rate at the glass transition temperature is chosen Ci=11.8K and C2 = 67.9K is obtained. The WLF dependence is typical for the dynamic glass transition (Fig. 21.6). It covers nearly 10 decades in the relaxation rate and scales with the calorimetric glass transition temperature as T(Tg) 10 Hz. The dynamic glass transition... 

During the isothermal ciystallization of PET at 97.5 ° C, that is, about 20 °C above its calorimetric glass transition temperature, the peak of the a-process is positioned at 104 Hz, and the shape of the dielectric loss curve is asymmetric as it is typically observed for the a-process of amorphous polymets. Hgure 15 shows contributions from the DC conductivity on the lower frequency side and a tail of the subglass p-process, whose peak exists above 1 MHz. As time passes, the peak value of the a-process deaeases and another peak appears at 10-100 Hz. The shape of the dielectric loss curve of the oo-process is quite different from that of the a-process the peak width is much broader than that of the a-process, and the peak shape is symmetric. Figure 16 shows that Ae of the a-process deaeases with time and eventually... 

Fig. 5. Experimental spectrum of atactic poly(propylene) recorded at T = 260 K, below the calorimetric glass transition temperature. The various resonances are considerably broadened and partly structured...

The PVC sample chosen as an experimental reference has a calorimetric glass transition temperature of Tg = 356 K and was purchased from Polyscience. The share of racemic diads was determined by solution -NMR... 

Experimental CP/MAS spectrum of PVC (b) (recorded at room temperature well below the calorimetric glass transition temperature) in comparison with simulation results for CHCl (c) and CH2 (d). The ne lines denote the contributions of the various geometries, according to Eq. (3.15), whereas the bold lines symbolize the overall simulation including the Gaussian broadening function, Eq. (3.16). The width of both resonances is well met. The small shoulder in the simulated methylene resonance is most likely due to a defective configurational statistics... 

As experimental references, a preferentially isotactic sample (p(mm) > 0.95) and a highly syndiotactic sample (p(rr) = 0.62, p(mr) — 0.30, p(mm) — 0.08) were selected. Crystalline phases were excluded for both samples by WAXS. Calorimetric glass transition temperatures were Tg = 330 K for the isotactic sample, and Tg = 400 K for the syndiotactic modification, respectively. 

Table 2. Calorimetric glass transition temperatures Tg and activation energies Ei of the mechanical yi and Y2-relaxation in in-situ and s f-IPNs...

Figure 6. Calorimetric glass transition temperatures, (o), and TSDC peak temperatures, (o), for the samples listed in Table 1...

Note r , dynamic mechanical peak temperature for glass transition (1 Hz) Tg, calorimetric glass transition temperature Pkww. KWW distribution parameter for glass-rubber relaxation FE V, fractional fiee volume based on density measurements DSC, differential scanning calorimetry. 

Kasapis S, Al-Marhoobi IM, Mitchell JR. Testing the validity of comparisons between the rheological and the calorimetric glass transition temperatures. Carbohydr Res 2003 338(8) 787-794. 

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