FIGURE 34.3 Shift factor approach and fit to Equation 34.1 for typical field data (modulus). [Pg.959]

Solution The temperature shift factor from 190°C to 230°C may be obtained from [Pg.354]

From the data in Fig. 4.8b, estimate the shift factors required to displace the data at 0 = 0.5 (consider only this point) so that all runs superimpose on the experiment conducted at 128 C at 0 = 0.5. Either a ruler or proportional dividers can be used to measure displacements. Criticize or defend the following proposition Whether a buffered aqueous solution of H2O2 and 1. containing small amounts of S2O3 and starch, appears blue or colorless depends on both the time and the temperature. This standard general chemistry experiment could be used to demonstrate the equivalency of time and temperature. The pertinent reactions for the iodine clock are [Pg.266]

We shall presently examine the physical significance of the shift factors, since they quantitatively embody the time-temperature equivalence principle. For the present, however, we shall regard these as purely empirical parameters. The following Ust enumerates some pertinent properties of a [Pg.258]

In order to allow for the effect of temperature on viscosity a shift factor, ar is often used. The Carreau equation then becomes [Pg.352]

Compo- sition No. Free PS, % Bound PS, % Filler (Aerosil) % Frequency cos-1 Shift factor b(c) used to reduce G (co) [Pg.55]

Use values of the constants for polystyrene from Table 4.4 to calculate the shift factors needed to connect those segments in Fig. 4.17 measured at 96.3 and 108.7°C, with the isotherm measured at Tg = 100.0°C. Are the values reasonable [Pg.261]

Williams, Landel and Ferry developed an empirical relationship for this type of shift factor. This has the form [Pg.117]

Table 4. Effect of specific surface area of filler and its concentration on concentration shift factors aci and ac for composites copolymer + ash (the reference concentration 10%) |

Table 16. Composition", frequency (co) beginning from which one may achieve coincidence of the G values and the shift factors b(c) at 190 °C [344] |

The time-temperature superpositioning principle was applied f to the maximum in dielectric loss factors measured on poly(vinyl acetate). Data collected at different temperatures were shifted to match at Tg = 28 C. The shift factors for the frequency (in hertz) at the maximum were found to obey the WLF equation in the following form log co + 6.9 = [ 19.6(T -28)]/[42 (T - 28)]. Estimate the fractional free volume at Tg and a. for the free volume from these data. Recalling from Chap. 3 that the loss factor for the mechanical properties occurs at cor = 1, estimate the relaxation time for poly(vinyl acetate) at 40 and 28.5 C. [Pg.269]

All amorphous polymers show remarkably similar results when values of log ay are plotted versus T - Tq. Manipulation of these data shows that the empirically determined shift factors can be fitted by the expression [Pg.259]

Williams and Ferryf measured the dynamic compliance of poly(methyl acrylate) at a number of temperatures. Curves measured at various temperatures were shifted to construct a master curve at 25°C, and the following shift factors were obtained [Pg.270]

Thus all the different temperature related data in Fig. 2.58 could be shifted to a single master curve at the reference temperature (7 ). Alternatively if the properties are known at Tref then it is possible to determine the property at any desired temperature. It is important to note that the shift factor cannot be applied to a single value of modulus. This is because the shift factor is on the horizontal time-scale, not the vertical, modulus scale. If a single value of modulus 7, is known as well as the shift factor ar it is not possible to [Pg.117]

Solution To use equation (2.76) it would be necessary to know the properties at - 10°C. In this example, the properties are known at 20°C which becomes the reference temperature (J1). The approach taken will be to get the shift factor at T2 — 60°C) and the shift factor at T — 20°C) and then subtract these to get the shift factor from T to 7. [Pg.118]

It was shown earlier that the variation of creep or relaxation moduli with time are as illustrated in Fig. 2.9. If we now introduce temperature as a variable then a series of such curves will be obtained as shown in Fig. 2.58. In general the relaxed and unrelaxed modulus terms are independent of temperature. The remainder of the moduli curves are essentially parallel and so this led to the thought that a shift factor, aj, could be applied to move from one curve to another. [Pg.116]

Polymers are a little more complicated. The drop in modulus (like the increase in creep rate) is caused by the increased ease with which molecules can slip past each other. In metals, which have a crystal structure, this reflects the increasing number of vacancies and the increased rate at which atoms jump into them. In polymers, which are amorphous, it reflects the increase in free volume which gives an increase in the rate of reptation. Then the shift factor is given, not by eqn. (23.11) but by [Pg.244]

See also in sourсe #XX -- [ Pg.93 ]

See also in sourсe #XX -- [ Pg.130 ]

See also in sourсe #XX -- [ Pg.458 ]

See also in sourсe #XX -- [ Pg.256 ]

See also in sourсe #XX -- [ Pg.55 ]

See also in sourсe #XX -- [ Pg.408 ]

See also in sourсe #XX -- [ Pg.85 ]

See also in sourсe #XX -- [ Pg.26 ]

See also in sourсe #XX -- [ Pg.46 ]

See also in sourсe #XX -- [ Pg.165 ]

See also in sourсe #XX -- [ Pg.228 ]

See also in sourсe #XX -- [ Pg.415 , Pg.416 ]

See also in sourсe #XX -- [ Pg.406 ]

See also in sourсe #XX -- [ Pg.129 ]

See also in sourсe #XX -- [ Pg.479 ]

See also in sourсe #XX -- [ Pg.110 ]

See also in sourсe #XX -- [ Pg.141 ]

See also in sourсe #XX -- [ Pg.33 ]

See also in sourсe #XX -- [ Pg.149 , Pg.173 ]

See also in sourсe #XX -- [ Pg.151 ]

See also in sourсe #XX -- [ Pg.223 ]

See also in sourсe #XX -- [ Pg.192 ]

See also in sourсe #XX -- [ Pg.27 ]

See also in sourсe #XX -- [ Pg.106 ]

See also in sourсe #XX -- [ Pg.101 , Pg.107 , Pg.109 ]

See also in sourсe #XX -- [ Pg.177 ]

See also in sourсe #XX -- [ Pg.7 , Pg.134 ]

See also in sourсe #XX -- [ Pg.269 ]

See also in sourсe #XX -- [ Pg.43 ]

See also in sourсe #XX -- [ Pg.407 ]

See also in sourсe #XX -- [ Pg.96 ]

See also in sourсe #XX -- [ Pg.134 ]

See also in sourсe #XX -- [ Pg.734 , Pg.735 ]

See also in sourсe #XX -- [ Pg.230 , Pg.235 , Pg.238 , Pg.265 , Pg.340 , Pg.362 ]

See also in sourсe #XX -- [ Pg.415 , Pg.416 ]

See also in sourсe #XX -- [ Pg.362 , Pg.456 ]

See also in sourсe #XX -- [ Pg.345 ]

See also in sourсe #XX -- [ Pg.377 , Pg.382 ]

See also in sourсe #XX -- [ Pg.114 , Pg.509 ]

See also in sourсe #XX -- [ Pg.638 ]

See also in sourсe #XX -- [ Pg.341 ]

See also in sourсe #XX -- [ Pg.407 , Pg.453 ]

See also in sourсe #XX -- [ Pg.566 , Pg.568 , Pg.569 , Pg.576 , Pg.577 ]

See also in sourсe #XX -- [ Pg.131 , Pg.132 ]

See also in sourсe #XX -- [ Pg.123 ]

See also in sourсe #XX -- [ Pg.116 ]

© 2019 chempedia.info