Abstract A number of diacylperoxides, peroxydicarbonates, peresters and dialkylperoxides with various substituents were chosen to investigate their homolytic decomposition under pressures of up to 3000 bar and high temperatures of up to 200°C, discontinuously in steel autoclaves, in an optical high pressure cell and in flow processes. The measurements, carried out in isododecane as solvent with a peroxide concentration of 1% by weight show that pressure has a strong influence on the decomposition: the half‐life time at 3000 bar is twice that at normal pressure. The pressure dependence, which varies according to the structure of the peroxide and the decomposition mechanism, is interpreted by means of the activation volumes. On the basis of the results, recommendations are made on the choice of peroxides suitable as polymerization initiators for application at high pressures and temperatures.
Der Einfluß der Estergruppe auf den Zerfall organischer Peroxide wurde an Perestern der Pivalin- und der Neodecansäure mit tert-Butyl-, tert-Amyl-, 1-Methyl-propylpentyl- sowie 1,1,4-Trimethylpentylresten bei Temperaturen von 393 bis 473 K und Drücken bis 3000 bar in einer Strömungsapparatur untersucht. Die Zerfallshalbwertszeiten nehmen erwartungsgemäß mit steigender Temperatur stark ab und mit steigendem Druck zu. Mit zunehmender Größe der Substituenten steigen sowohl die Zerfallsgeschwindigkeiten als auch die Aktivierungsenthalpien. Dieser überraschende Effekt kann durch die Vergrößerung der Aktivierungsentropie und des Aktivierungsvolumens erklärt werden. Influence of Substituents on the Enthalpy, Entropy and Volume of Activation in the Decomposition of Organic Peresters The influence of the ester group on the decomposition of organic peroxides was studied on peresters of the pivalic and neodecanoic acid with tert-butyl, tert-amyl, 1-methyl-1-propylpentyl and 1,1,4-trimethylpentyl groups at temperatures of 393 to 473 K and pressures up to 3000 bar using a flow method. As expected the half-live times decrease with increasing temperature and increase with rising pressure. With increasing bulkiness of the substituents the rates of decomposition as well as the enthalpies of activation increase. This surprising fact can be explained by the simultaneous increase of the entropies and the volumes of activation.
