Effect of Elevated Temperatures

Here we must distinguish between the effect of temperature both before and after the development (drying of the plate) and the effect of heat during chromatography. In the first case, the choice of a more suitable solvent system can prevent loss or decomposition of volatile or temperature-sensitive test substances. In the second case, development should be performed at lower temperatures, e.g. in a TLC Thermo-Box (see Section 4.2.3 Effect of Temperature in Chromatography ). 

---

Table 3.36. Effect of Elevated Temperatures on Strength of Titanium and Alloys [35]...

The Effect of Elevated Temperature on the Lower Flammable Limit of Combustible Solvents as Encountered in... 

Table 5-5 Effects of elevated temperature and chemical agents on stability of plastics...

In the case of reservoir systems that rely on the cohesivity of the blend due to interparticle interactions, studies are required on vibrational stability in simulated storage, transport, and use tests, including determination of the effects of elevated temperature and humidity. 

Figure 32. Effect of elevated temperatures on dissolution from Li1.05Mn1.95O4 stored in LiPFe/EC/DMC (2 1). The Mn + concentrations in the electrolytes were determined by atomic absorption spectroscopy. (Reproduced with permission from ref 301 (Figure 1). Copyright 1999 The Electrochemical Society.)...

Much of the recent impetus for temperature control has focused on exploiting the effects of elevated temperature on viscosity and diffusion coefficients [2], These lead to faster separations and also allow smaller particle diameters to be employed with conventional HPLC hardware. As the viscosity of solvents decreases, the column pressure drops. This can be exploited by using faster flow rates and smaller particle diameters. All of this leads to faster separations. In one experiment in this laboratory, a separation which required 8 min at room temperature was reduced to 2 min at 50°C without changing the column. Speed enhancements of as much as 50-I00-fold have been reported [13] as shown in Figure 9.1. 

A less obvious effect of elevated temperature is on plate height. The equation describing plate height (H) can be written as follows [14] ... 

The other significant effect of elevated temperature is in the capacity factor, k. In most cases, k decreases as temperature increases, but there are enough exceptions to this general rule that a more detailed discussion is needed. This will be addressed in Section 9.3. 

Heat resistance - The property or ability of rubber articles to resist the deteriorating effects of elevated temperatures. 

The target consists of a printed circuit board with two circuits. One circuit is exposed. The second circuit is protected and is used to compensate for the effect of elevated temperature on the electrical resistance of the circuit. The target is removed from the chamber 1 h after the start of a test and the reduction of the electrical resistance of the exposed circuit is measured. The target is then exposed to an atmosphere of 23°C and relative humidity of 75% for 24 h. The electrical resistance is measured again after the 24 h post-test exposure. The electrical resistance measurements are converted to the equivalent reductions in metal thickness, C, and C2 respectively, expressed in nanometers. 

In ceramics, the term firing implies heat treatment of green ware which is thereby strengthened. In this way its shape is fixed and its characteristic properties are created. The process of spontaneous strengthening of fine-grained porous bodies through the effect of elevated temperature is called sintering. 

Effect of Elevated Temperature on Decay of Physical Crosslinks. 

Abe, T. Messner, W.C. Reed, M.L. Effects of elevated temperature treatments in microstructure release procedures. J. Microelectromech. Syst. 1995, 4, 66-75. 

The effect of elevated temperatures or certain solvents is to remove only part of the film adsorbed on ordinary metal surfaces the rest of the adsorbate is tenaciously retained. Desorption from noble metals such aS platinum is total. 

Only a few studies concerning the temperature dependence of sensitized cis trans isomerization have been reported [2, 108, 184, 196, 236], A small effect of elevated temperature on ([c]/[t])scns for stilbene has been found [2,196] at 59°C the photostationary state is somewhat richer in cis isomer than at 28°C if sensitizers with Er > 222 kJ mol-1 are used. However, Yamashita et al. [184] have obtained activation energies of 2 and 3kJmol 1, respectively, for benzophenone-sensitized trans- cis and cis- trans isomerization (25 to -78°C, liquid state) they observed that both reactions still proceed even at — 196°C (solid state). In contrast Malkin and Fischer [108] found no temperature dependence of the benzophenone-sensitized isomerization down to — 140°C. 

S.J. Balsone The Effect of Elevated Temperature Exposure on the Tensile and Creep Properties of Ti-24A1-1 INb In Oxidation of High Temperature Interinelallics.T. Grobstcin and J. Doychak eds.,TMS, 1989, p. 219. 

Figure 2 shows the reactor, built by Autoclave Engineers, Inc. It was constructed of Type-316 stainless steel so that it could be used later to test the effects of elevated temperatures on catalyst stability. A magnetic drive rotates the stirrer shaft. The reactor has an inside depth of 12 in. and an inside diameter of 3 in. For CSTCR operation, two inserts are installed which reduce the inside depth to 2-13/16 in. 

Sisler, E.C. Effects of elevated temperature on tobacco leaf respiration and 0-phenol oxidation Tob. Sci. 15... 

B.I. Shekhter et al, Effect of Elevated Temperatures and Hydrostatic Pressure on the Detonation Characteristics and Sensitivity of Explosives , FizGoreniyaVzryva 1978,14 (5), 163-67 (Russ) CA 90, 57482 (1979) [Expts were performed with elongated cartridges of HMX inserted in 0.5mm wall thickness A] castings which were exposed to a temp range of 150—230° and pressures of 80—ISOMPa. Ati 170°, the deton vel Increased by 3—5%. Above 170°, the deton vel decreased because of the thermal decompn of HMX. The saturation of the HMX cartridges with liq at elevated press and temps increased the sensy of HMX]... 

The effect of elevated temperatures resulting from the energy released by the radioactive decay must be included in the evaluation of release and near Held migration (i.e. within the repository volume). Elevated temperatures could alter the geology as well as the chemical speciation and solubility of the released nuclides. If the temperature exceeds the boiling point of water in the fluids, it would result in a drier repository with reduced or no release and migration. 

Mukhopadhyay R. and S.K. De. 1978. Effect of elevated temperature on the unaccelerated and accelerated sulphur vulcanization of natural rubber. Rubber Chem. Technol. 51 704-17. 

Manothermosonication (MTS), a combined treatment of heat and nltrasonnd nnder moderate pressure, is another alternative to conventional heat treatment in order to inactivate enzymes and microorganisms [120-122], The ultrasound generates the cavitation or bnbble implosion in the media. This implosion can cause inactivation of the enzyme and destrnction of microorganisms. The simultaneons pressnre treatment maximizes the intensity of the explosion, which increases the level of inactivation. The MTS technique avoids the adverse effects of elevated temperatures on quality and also resnlts in reduced energy requirements and therefore rednced costs. 

---