High-temperature short time replacements

There are some obvious opportunities where tailor-made natural aromas or precursors can find immediate application. These include direct application in formulated foods and beverages, as well as processes where precursors release the desired aromas (e.g., high temperature/short time operations). There are many other opportunities, especially with regard to natural aromas as replacement for synthetic ones. But the biggest opportunity is to give consumers what they want — a high quality natural aroma, readily available, at reasonable cost. 

The very rapid oxidation of phenols by solvent radical cations can be expected to yield phenol radical cations as the first products. These species are short-lived, except in highly acidic solutions, and were not observed in the microsecond pnlse radiolysis experiments described above. They were detected, however, in frozen matrices and with nanosecond pulse radiolysis Gamma irradiation of phenols in w-butyl chloride or in l,l,2-trichloro-l,2,2-trifluoroethane (Freon 113) at 77 K produced phenol radical cations, which were detected by their optical absorption and ESR spectra . Annealing to 133 K resulted in deprotonation of the radical cations to yield phenoxyl radicals. Pulse radiolysis of p-methoxyphenol and its 2,6-di-fert-butyl derivative in w-butyl chloride at room temperature produced both the phenol radical cations and the phenoxyl radicals. The phenol radical cations were formed very rapidly k = 1.5 x 10 ° M s ) and decayed in a first-order process k = 2.2 x 10 s ) to yield the phenoxyl radicals. The phenoxyl radicals were partially formed in this slower process and partially in a fast process. The fast process of phenoxyl formation probably involves proton transfer to the solvent along with the electron transfer. When the p-methoxy group was replaced with alkyl or H, the stability of the phenol radical cation was lower and the species observed at short times were more predominantly phenoxyl radicals. 

IFP s paper on their Spanish plant described their hydrocracked stocks as having about the same stability to oxidative storage conditions as those from solvent refining. This has generally not been industry experience elsewhere. In fact, unfinished first-stage hydrocracked base oils, waxy or dewaxed, have been found to darken in color over relatively short times and form haze or insoluble deposits, and these effects are accelerated when samples are exposed to high (about 100°C) temperatures or sunlight in so-called window tests, which were later replaced by more specific exposure to ultraviolet (UV) sunlamps. This was... 

At each reload, the fuel failure fraction in the core decreases due to the replacement of the oldest one half of the fuel in the core with fresh fuel. The results indicated that the predicted fuel particle failure due to temperature effects was very small even at the high temperature points (at the outer boundary of the active core in the proximity of the control rods) since such high fuel temperatures are maintained for only short periods of time. The predicted pressure vessel failure was negligible. Thus, the overall particle failure was predicted to be caused by manufacturing defects, primarily by particles with missing buffer layers. 

All materials have their limitations and the solution to high-temperature problems is often a compromise between careful materials selection when the cause of a problem is known, process control in order to impose a safe limit for temperature or gas composition, for example, and better design specifications to recognize mechanical constraints at elevated temperature or resulting from thermal cycling. The ultimate choice will be a compromise based on what is available and how much it costs. In some cases it is rational to accept a short life expectancy with a high reliability factor where the component is replaced on a planned time schedule [1]. 

Some spun fibers are reported to be very useful in bone implants and similar applications, where it is desirable that a fiber degrade and be absorbed in a relatively short time. Here, these fibers would lend green strength to a composite that is ultimately replaced by normal bone. Some more recent systems are also showing some promise as high-temperature spun amorphous phosphate fibers. This utility may eventually be possible. 

Until now the use of crosslinking systems based on thiuram disulphide for compounds which reach high temperatures has been difficult owing to the inadequacy of the scorch times. However, Leibbrandt has drawn attention to the development of systems comprising tetramethyl thiuram disulphide (or preferably dimethyl diphenyl thiuram disulphide), N-morpholinyl-2-benzothiazyl sulphenamide, a special retarder (Vulkalent E), and 0-5-0 8 phr of sulphur which, especially in the case of NBR, combine high processing safety with short vulcanisation times. The thiuram disulphide can be replaced by other sulphur donors (see Table 3 and Fig. 9). 

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