The homopolymerization la was attempted with anionic (nbutyllithium), cationic (titanium tetrachloride), and radical (AIBN; benzoyl peroxide; benzoin methyl ether, hv) initiators. In each case, no polymer was obtained and the monomer was recovered.
ZUSAMMENFASSUNG:Um die charakteristischen Unterschiede bei der Kristallisation von gequollenen und ungequollenen Hochpolymeren zu finden, wurde amorphes Polyathylenterephthalat bei 20' bzw. 3OoC bis zur Sattigung in Methanol gequollen und anschlieoend durch eine Erhohung der Temperatur in einem mit Methanol gefiillten Dilatometer zur Kristallisation gebracht. Aus der Volumenanderung wurde der zeitliche Verlauf der Kristallisation bestimmt. Bei der Auswertung der Messungen nach AVRAMI wurden charakteristische Abweichungen von den iiblicherweise gefundenen Geraden beobachtet. Diese kann man damit erklaren, da5 das aus den Kristalliten ausgestoflene Quellmittel an der Oberflache der Spharolithe in zunehmendem MaGe angereichert wird, wodurch sich die Spharolithwachstumsgeschwindigkeit laufend erhoht.Des weiteren wurde eine Gleichung zur Beschreibung des zeitlichen Verlaufs der Kristallisation abgeleitet unter der Annahme, da13 wahrend der Kristallisation eine zusatzliche Menge an Quellmittel in die Probe eindiffundiert. Es zeigt sich, da5 unter diesen Umstanden in vielen Fallen ein Kristallisationsverlauf auftritt, der in der Avmi-Auftragung in erster Naherung zu Geraden fiihrt. Die Quellung bewirkt dabei vor allem eine Parallelverschiebung dieser Geraden.
SUMMARY:I n order to determine the characteristic difference in the crystallization of unswollen and swollen polymers, amorphous polyethyleneterephthalate was swollen in methanol at roomtemperature. Afterwards it was crystallized in a dilatometer filled with methanol by raising the temperature. The time dependence of crystallinity was measured a t different temperatures. The results were evaluated according to the theory of AVRAMI. It was found that there occur characteristic deviations from the straight lines usually obtained. These deviations can be explained by the fact that the swelling agent expelled from the crystals accumulates a t the surface of the spherulites so that the growth rate of the spherulites increases during crystallization.We have also derived an equation for the time dependence of the crystallization process under the assumption that an additional amount of swelling agent penetrates the sample
The flavors produced by stewing, broiling, or roasting make meat one of the most popular items in the human diet. No "key" compounds are responsible for meat flavors. However, protein degradation appears essential to the development of meat flavor precursors whose interactions are responsible for characteristic meat flavors. This review examines simulated meat flavor systems based on the protein degradation products produced by acid hydrolysis using strong mineral acids, yeast autolysis, and enzyme degradation of natural meat proteins by pure proteinases. In addition, the contributions to meat flavor made by heating protein hydrolysates in the presence of sugars and organic sulfur compounds are reviewed. This paper also describes the work in applied meat flavor research carried out in the former East Germany.
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