Temperature for polymers

The Arrhenius equation holds for many solutions and for polymer melts well above their glass-transition temperatures. For polymers closer to their T and for concentrated polymer and oligomer solutions, the WiUiams-Landel-Ferry (WLF) equation (24) works better (25,26). With a proper choice of reference temperature T, the ratio of the viscosity to the viscosity at the reference temperature can be expressed as a single universal equation (eq. 8) ... 

Plots of loss modulus or tan 5 vs temperature for polymers give peaks at energy absorbing transitions, such as the glass transition and low temperature secondary transitions (Fig. 20). Such plots are useful for characterizing polymers and products made from them. 

Figure 17.1 and Table 17.1 give melting points for metals and ceramics and softening temperatures for polymers. Most metals and ceramics have high melting points and, because of this, they start to creep only at temperatures well above room temperature... 

For benzene - one of the best-suited calibration fluids - the error is 4% at room temperature. For polymers errors of up to 65% (polystyrene at room temperature) have been verified both theoretically and experimentally. 

One of the central problems in the study of diffusion is to evaluate D for a given system as a function of such parameters as penetrant concentration and temperature. For polymer-penetrant systems with which we are concerned in this article two experimental methods are typical for this purpose. They are the sorption method and the permeation method. 

Figure 11. Mechanical loss vs. temperature for polymer K and its 50/50 blend with aMS/AN copolymer...

This method has given results of acceptable reproducibility with a wide variety of organosiloxane polymers, although each type of polymer has its optimum temperature of oxidation in the combustion tube. In general, the oxidation temperatures for polymers with... 

An increase of the craze stability of tensile-induced crazes with rising M has been noted in various glassy polymers. In a study made on thin PS films by Berger and Kramer the craze extension ratio was determined at various temperatures for polymers of varying M. For measurements made at room temperature, X varied little with molecular weight but, as the temperature was raised, and chain disentanglement processes became more probable, the situation changed. For example, at 50 °C,... 

Camacho-Zuniga, C. and Ruiz-Trevino, F.A. (2003) A new group contribution scheme to estimate the glass transition temperature for polymers and diluents. Ind. Eng. Chem. Res., 42, 1530-1534. 

An alternative procedure would be to mix the reactants at a temperature above the ceiling temperature for polymer formation. After a given period of time (during which peroxides would be destroyed harmlessly) the mixture would then be cooled to the desired polymerization temperature and polymerization initiated. This procedure is quite laborious and time consuming and was not given serious consideration. As will be shown later, the addition of a small amount of SO2 to the olefin leads to kinetic complications. Subsequent modification of the purification apparatus and procedure proved to be simple and efficient and rendered the addition of SO2 unnecessary. 

Figure 3.58. An example showing (a) the variation in molar mass with extent of reaetion and (b) the variation of modulus versus temperature for polymers with three different crosslink densities, as determined by DMTA. Adapted from Figures 1 and 4 (Labana, 1985). Copyright (1985). Reprinted with permission of John Wiley and Sons, Inc.

Harismiadis, V.I. et al.. Application of the van der Waals equation of state to polymers. III. Correlation and prediction of upper critical solution temperatures for polymer solutions. Fluid Phase Equilibria, 100, 63-102, 1994. 

FIGURE 82 Response to shear stress, shown here as the polymer HLMI/MI ratio, as a function of catalyst activation temperature for polymers made in the slurry process with Cr/silica-titania catalyst. Reaction temperature was varied (102-110 °C) to produce three series of polymers of constant melt index. (Compare with Figure 83.)... 

Viscosity Relations. Several equations have been proposed to describe the dependence of the viscosity of the system on temperature. For polymer systems the Williams Landel-Ferry (WLF) equation is often used. It reads... 

The calculated Tg of PVC containing 8 weight %. C02, the limiting solubility at 25° and unit activity, is about 27°C. Thus, the solubility and Cg of C02 in PVC at room temperature are nearly equal i.e., liquid C02 can plasticize PVC virtually into the rubbery state at room temperature. For polymers in which C02 is more soluble, such as PMMA or poly(vinyl benzoate), depression of the glass transition to below room temperature, as evidenced by the isotherm inflections, is quite in accord with the predicted high plasticizing efficiency of C02... 

Another group of thermally stable polymeric materials for electronic application includes poly(ether-imide-benzoxazolejs. Mercer and McKenzie [228] prepared the polymer by polycondensation of 2,2 -bis[2-(4-aminophenoxy)benzoxazole-6-yl] hexafluoropropane with pyromellitic, biphenyl, benzophenone etc., followed by thermal imidization of polyamic acid films. The polymers showed an onset temperature for polymer degradation in the range of 424°-456°C and glass transition temperatures in the range of 299 -337°C. 

Table 4.5 Approximate glass transition and melting temperatures for polymers ...

Figure 24. Spontaneous polarization versus temperature for polymer XVI.

Whenever, the thermodynamic Debye temperature for polymers exceeds their condensed-state temperature. Therefore the quantum statistics of atomic vibrations should be taken into account. As the F (6/T) function has no a precise analytical form, the true activation parameters cannot be evaluated precisely. Nevertheless, in the Tb < T < range, only two vibrational modes, those with the Vt and Vb frequencies, are shown to give the greatest contributions in... 

Some well established models that correlate free volume fraction to the glass transition temperature for polymers support the free volume concept. The fractional free volume of a liquid, f, is defined as f=Vi/vq, where Vj is the free volume and Vg is the occupied volume. The empirical Boyer-Sumha mle relates the ftee volume fraction, f to the cubic... 

Figure 10.34. Various kinds of concentration dependencies of the glass transition temperature for polymer-plasticizer systems. 1 - PVC-ethyl stearate, 2 - PVC-dibutyl phthalate, 3 - butadiene rubber SCD-trans-former oil, ° 4 - line connecting the points corresponding to the glass transition temperature of transformer oil and the point corresponding to the system 3 with the largest fraction of plasticizer.

Fig. 3. Orientational order parameter S as a function of temperature for polymer la. 

Figures 14.34 —14.36 show the temperature dependence of the stiffness constants of polymers A, B and C, respectively. As a result of the high frequency (4 GHz) of Brillouin scattering measurements, the sound absorption maximum (and hence the dynamic glass transition temperature for polymer C was found to be located at 390 K,...

Evenhuis CJ, Guijt RM, Macka M, Marriott PJ et al (2005) Internal electrolyte temperatures for polymer and fused-silica capillaries used in capillary electrophoresis. Electrophoresis 26 4333-4344... 

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