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SynopsisThe oxidative degradation of isotactic polypropylene films coated on well-defined Cu(CuzO), Cu00.67, and CuO films in a temperature range of 96120°C in a quartz-spoon-gauge-reaction vessel was studied, This catalytic reaction has been compared with the oxidation of polypropylene without copper or oxide films. The reaction vessel contained, if needed, P~0 5 and/or KOH as "getters" for HzO and COz; these substances could be monitored continuously. Cu(Cuz0) films were transformed during oxidation of the polymer to yellow CuO0.67 below l00OC and above this temperature to black CuO in the presence of H20 and Con, whereas in the absence of these compounds CuO was formed below 100°C and C U O~.~~ a t 120°C. Characteristic autoxidation curves obtained in the absence of HzO and COz showed induction periods that were shorter for copper oxide-polymer interfaces than for glass-polymer interfaces (i.e., for uncatalyzed oxidation). Abnormalities were observed for Cu (Cuz0)-polymer interfaces because of further oxidation of Cu during the reaction. The rates of oxygen consumption were faster for CuOo.67-polymer and CuO-polymer than for the uncatalyzed reaction; the catalytic action of Cu00.67 was somewhat larger than that of CuO. The important observation was made that the mechanism of oxidation is not the same in the absence and presence of reaction products; that is, HzO and Con. This was confirmed by ion beam scattering experiments, which also revealed that an oxidation-reduction process takes place a t Cu and their oxide interfaces. A mechanism for the catalytic oxidation process, based on the ease by which copper ions are released from the metal oxides a t the interface, was formulated. These ions diffuse subsequently as cations of carboxylate anions into the bulk of the polymer. Arrhenius equations of oxygen consumption are given for all cases; the energy of activation calculated for the initiation of the uncatalyzed oxidation agrees with its literature value. The energy of activation for the initiation of the catalyzed reaction was a few kilocalories lower than that for the uncatalyzed reaction. Catalytic action is mainly operative for the initiation reaction at the interface and for the decomposition of hydroperoxides by copper ions. Preventing the delivery of copper ions to the polymer would be the most efficient way of inhibiting the catalysis.

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Poly(α‐methyl styrene), produced in various ways, was degraded in a closed system over a range of temperatures from 260 to 320°C. in the absence of air. Except for the initial parts of the degradation reaction (up to about 20% conversion to monomer), all samples had a random initiation reaction, followed by a depropagation step with a number‐average kinetic chain length larger than the number‐average polymer chain length. The energies of activation, after the initial part of the degradation, were all of similar magnitude (ca. 63 kcal./mole) and agreed with values found by previous workers. A few samples showed distinct maxima during the first 20% conversion in their curves of rate of monomer versus conversion, whereas others showed only constant rates or slowly decreasing rates during the initial periods of the reaction. The latter rates can be accounted for by chain‐end initiation (kinetic chain length ≫ polymer chains) or by a random initiation process followed by depropagation and disproportionation as termination reaction. The initial maxima found in some samples could be accounted for by a theory of random initiation in conjunction with a number‐average kinetic chain length larger than the polymer chains, which is inhibited by a reaction of polymer radicals with catalyst fragments. The inhibitor is consumed during the reaction.

IR specular reflectance spectra with respect to hydrogen peroxide formation during uncatalyzed and Cu (oxide)‐catalyzed oxidation of isotactic Polypropylene films have been measured as function of time and temperature (90–130°C). Energies of activation for the various cases have been obtained. The originally proposed kinetic scheme based on oxygen‐absorption measurements has been modified in order to accommodate the spectroscopical results. The amount of ROOH groups present at any time on the polymer is very small, indicating relatively slow rates of ROOH formation and fast rates of their decomposition. The kinetic scheme fits well the experimental data. However, the reasons for the variations of the relevant energies of activation obtained for the catalyzed oxidation in absence and presence of the main volatile reaction products, H2O and CO2, are not yet understood, i.e., the mechanism needs further investigations.