Effect of thermal history

Fig. 4. Effect of thermal history on low temperature thermal expansion of vitreous siUca (143), where (-), (---), and (—) represent glasses having ftctive...

Effect of Thermal History. Many of the impurities present in commercial copper are in concentrations above the soHd solubihty at low (eg, 300°C) temperatures. Other impurities oxidize in oxygen-bearing copper to form stable oxides at lower temperatures. Hence, because the recrystallization kinetics are influenced primarily by solute atoms in the crystal lattice, the recrystallization temperature is extremely dependent on the thermal treatment prior to cold deformation. 

In the present work, we use quantitative solid-state 13C NMR spectroscopy to study the polymerization process of multiacrylates and the effects of thermal history/aging on the free radical life in polymultiacrylates. 

EFFECT OF THERMAL HISTORY ON THE RHEOLOGICAL BEHAVIOR OF THERMOPLASTIC POLYURETHANES... 

The effects of thermal history on the nucleation characteristics of CaCl2 6H20 melt without nucleation agent and the same melt with nucleation agent were studied experimentally by the cooling method at constant rate of IK/min. 

Thermal Expansion. Most manufacturers literature (87,119,136—138) quotes a linear expansion coefficient within the 0—300°C range of 5.4 x 10"7 to 5.6 x 10 7 /°C. The effect of thermal history on low temperature expansion of Homosil (Heraeus Schott Quarzschmelze GmbH) and Osram s vitreous silicas is shown in Figure 4. The 1000, 1300, and 1720°C curves are for samples that were held at these temperatures until equilibrium density was achieved and then quenched in water. The effect of temperature on linear expansion of vitreous silica is compared with that of typical soda—lime and borosilicate glasses in Figure 5. The low thermal expansion of vitreous silica is the main reason that it has a high thermal shock resistance compared to other glasses. 

The density of bulk milk (4% fat and 8.95% solids-not-fat) at 20°C is approximately 1030 kg m 3 and its specific gravity is 1.0321. Milk fat has a density of about 902 kg m " 3 at 40°C. The density of a given milk sample is influenced by its storage history since it is somewhat dependent on the liquid to solid fat ratio and the degree of hydration of proteins. To minimize effects of thermal history on its density, milk is usually prewarmed to 40-45°C to liquify the milk fat and then cooled to the assay temperature (often 20°C). 

The most important point is the effect of thermal history upon the equilibrium level of cobalt and zinc ions in solution. Within experimental error, the results obtained with the 45 °C—two day systems are identical to the 45°C systems which had received a prior one-day treatment at 5°C. The duration of the experiments has very little effect upon the equilibrium distribution, as evidenced by the fact that the results obtained by longterm equilibrations at both temperatures and for both ions were nearly identical to those shown in Table III. Most important however is the finding that the equilibrium levels of cobalt and zinc at 5°C are significantly higher than these which are obtained after a 45°C treatment. This indicates that the 5°C distribution over the various possible sites, as induced by a 45°C pretreatment, differs from the normal low-temperature distribution in that a significant portion of the adsorbed bivalent ions which participate in the 45°C equilibrium no longer do so at 5°C. In other words, when returned to 5°C, part of the solid-phase metal ions appear irreversibly sequestered in sites where they are out of reach at low temperature. 

Figure 18 shows the effects of thermal history on the mechanical dispersion peaks in Fiberite 934 epoxy composites. The as-fabricated materials show by far the largest damping which spans from —100 °C to 20 °C. Postcuring completes the crosslinking and results in significantly lower-damping material. 

The relationship between the physical properties of profiles extruded from flexible PVC compounds and the extrusion melt temperature was studied. The properties included tear resistance, tensile properties, brittleness temperature and compression set. The effect of thermal history on surface characteristics of the extrudate, such as surface roughness and gloss, and the relationship of the latter with the processing morphology were also examined. An increase... 

Effects of Thermal History. One of the most useful and fundamental parameters defining the state of a polymer is its enthalpy (or specific heat). Considerable evidence has been adduced to show that the thermal characteristics of glassy polymers such as PC are sensitive to thermal... 

Danch et al. studied the effect of thermal history on the assignment of the glass transition event associated with the biaxial orientation of the smectic... 

Structure development rate (SDR), defined as AG /At, can be measured under isothermal conditions, at different aging temperatures (cure curves), and also during the gelation process promoted by decreasing the temperature of the biopolymer dispersion (non isothermal conditions) (Rao and Cooley, 1993). The analysis of structure development rates (SDRs) under isothermal conditions, as opposed to non-isothermal conditions, can be very useful to avoid the non-equilibrium effects and the effect of thermal history of the system. 

Fig. 5 Effect of thermal history on aggregate size in Zn-EMAA the mean diameter for Zn-EMAA neutralized to 29% (circles) and 78% (diamonds) with Zn increases slightly with annealing time. (Reprinted with permission from Ref.. Copyright 2004 American Chemical Society.)...

Effect of Thermal History of Austenitic Stainless Steels on Susceptibility to Intergranular Corrosion. The time dependence for the local depletion of chromium sufficient to cause susceptibility to intergranular corrosion as functions of temperature and carbon content is of the form represented in Fig. 7.54 (Ref 83). The curves are typical of type 3xx alloys with nominal chromium concentrations of 17 to 25 wt% and, since they represent times for initiation of intergranular corrosion,... 

Effect of Thermal History and Impurities on Phase Transitions in Long-Chain Fatty Acid Systems... 

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