Time-temperature window

Because a high rate of deformation corresponds to a short time, we can see that the rubbery behaviour is manifested only within a certain time-frame. It is manifested within a certain temperature-frame also. Putting the time and temperature frames together, it is called the time-temperature window . Only when a polymer is within this window, does it exhibit rubbery behaviour. Outside of the window at the higher rates (shorter times) or... 

When the mill processability is in Region II, it is within the time-temperature window, which defines the rubbery state. The Region I is the border (transition) between the... 

C/s-1,4-butadiene rubbers (c/s-l,4-BR) tend to go into Regions III and IV, even though they are very long and thin molecules, 100% of their MW being in the main chain. This is because their T, is very low, -112 -120 °C. The normal milling temperature lies at the upper border of the time-temperature window. 

A more recent process, the P2 etch [60], which uses ferric sulfate as an oxidizer in place of sodium dichromate avoids the use of toxic chromates, but still provides a similar oxide surface morphology (Fig. 15) allowing a mechanically interlocked interface and strong bonding [9]. The P2 treatment has wide process parameter windows over a broad range of time-temperature-solution concentration conditions and mechanical testing confirms that P2-prepared surfaces are, at a minimum, equivalent to FPL-prepared specimens and only slightly inferior to PAA-prepared surfaces [61]. 

Time-temperature superposition [10] increases the accessible frequency window of the linear viscoelastic experiments. It applies to stable material states where the extent of reaction is fixed ( stopped samples ). Winter and Chambon [6] and Izuka et al. [121] showed that the relaxation exponent n is independent of temperature and that the front factor (gel stiffness) shifts with temperature... 

Figure 5 Time-resolved IR thermographic imaging of the enantioselective hydrolysis of epoxide (48c) catalyzed by >S,//-(50a-c) after (a) 0, (b) 2.5, (c) 4, (d) 5, (e) 7, (g) 8, (h) 15, and (i) 32 min. In (f) the same images is shown as in (e), except that the temperature window ranges over 10 K. The bar on the far right of each image is the temperature/colour key of the temperature window used (°C).SS...

The purpose of tip annealing is to remove the contaminants and oxides without causing blunting. Because tungsten has a very high melting temperature (3410°C), the temperature-and-time process window is wide. 

From bench-scale experiments it seems that the effect of finite-rate mixing on SNCR is to narrow the temperature window for the process at high temperatures. Assess whether this is in agreement with model predictions, using an estimated mixing time (90%) of 100 ms. 

Figure 8.35. Porosity versus time-temperature index of maturity (TTI) for various carbonate rock units. The TTI values are based on Lopatin s (1971) method. The onset and end of oil generation (the "oil generation window") in terms of TTI units are from Waples (1980). The log linear equations of best fit between porosity and TTI data are also shown. = porosity. (After Schmoker, 1984.)...

Figure 8.37. Burial history plot for Helderberg Group rocks and other strata. Helderberg Group is shaded, whereas the base of Ordovician strata, base of Silurian strata and base of Mississippian strata are shown as thin lines marked O, S and M. Dashed lines are time-temperature indices of maturity (TTI see Waples, 1980). The oil generation window represents the necessary conditions of time and temperature for potential oil generation. The 50° oil preservation deadline is the upper TTI limit for occurrence of oil with API gravity of 50°. (Modified from Dorobek, 1987.)...

The similarities of the isothermal curves permit the construction of a master curve (thick dashed curve in Figure 13.4) for any reference temperature To by the well-known time-temperature superposition principle [30,36]. The superposed master curve expands the experimentally accessible a> window for these examples by about three decades relative to that measured at any single temperature. This wider window is critical to understanding fabrication performance. 

Birefringence setups can be designed to characterize molten materials undergoing isothermal homogeneous flow. The ranges of strains and strain rates also often coincide with those of rheometers, and consequently may be limited relative to those used in fabrication. Similarly, time-temperature superposition approaches may be used to expand the rate window. State-of-the-art setups suitable for rapid screening of new materials with research-scale quantities (5-20 g) are available for shear flow [72] and startup of uniaxial extensional flow [73,74]. 

The use of this time-temperature equivalence allows one to obtain "master curves" at a reference temperature, which enlarges considerably the experimental window. For glass-forming materials such as polystyrene, polymethylmetacrylate, polycarbonate, polymerists describe the shift factor aj in terms of the WLF equation ... 

The screen for each chemical kinetic calculation simultaneously displays a variety of characterizations in multiple windows and allows analysis of time/temperature-dependent species and reaction information including species concentrations, species steady-state analysis, individual reaction rates, net production/destruction rates, reaction equilibrium analysis and the temperature/time history of the system. The interactive user-sorting of the species and reaction information from the numerical simulations is mouse/cursor driven. An additional feature also allows interactive analysis and identification of dependent and independent species and reaction pathways, on-line reaction network analysis and pathway/flowchart construe-... 

Once the NO has been formed in the combustion process, if it is not removed it largely converts to NO2. This is the source of the brownish plume often seen from power plant stack discharges. Unlike sulfur, it is not easily reacted with absorbents to form a solid sludge. Instead, it is catalytically reduced with ammonia or urea to form N2 and water. This catalytic reduction requires injection of the reductant into the flue gases within a particular temperature window, with adequate residence time and catalytic surfaces to complete the reduction process. This can be integrated with scrubbers for other materials, such as sulfur and... 

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