Diffusion coefficients of Cu2+ in the form of its carboxylate have been measured in isotactic polypropylene as a function of temperature (90–128°C) and extent of preoxidation. Diffusion take place from the metal catalyst/polymer interface into the bulk polymer. The diffusion is dependent on the extent of preoxidation and temperature but not on the type of catalyst (Cu, CuO, CuO0.67). Analysis of polymer sections for Cu2+ ions was carried out with a selective Cu2+ electrode. Diffusion in isotactic polypropylene is about 1000 times faster than in lowdensity polyethylene. The carboxylate anion appears to have about 7 C‐atoms for diffusion in isotactic polypropylene compared with 29 C‐atoms for low‐density polyethylene.

SynopsisThe kinetics and mechanism of H 2 0 and CO, evoluticjn during uncatalyzed and cop pedoxidekatalyzed (Cu, CuO, C U O~.~) oxidation of isotactic polypropylene have been investigated in detail for various catalysts over a range of temperatures (90-1WC). These volatilea were determined chromatographically; HZO and CO, represent the main volatiles of the oxidation, comprising about 80 mol % of all volatiles. Uncatalyzed oxidation evolves ca. 1 mol of H 2 0 and 1 mol of CO, for each unit mole of polymer oxidized, while catalyzed oxidation produces 2 mol of H20 and ca. 1.2 mol of CO, for each unit mole of polymer. These results indicate that secondary as well as tertiary H atoms on the polymer chains are involved in hydroperoxide formation and decay. The oxidation mechanism has been formulated and evaluated on this basis. It consists essentially of two parallel oxidation reactions involving tertiary and secondary g r o u p (H atoms and hydroperoxides), respectively. The mechanism can be represented by firstand peuddht-order reactions in series: (1) oxygen absorption showing induction periods; (2) hydroperoxide formation and decay (plateaus are reached); (3) H 2 0 evolution from the decay of hydroperoxides; and (4) subsequent COP production involving chain scission. Arrhenius parameters for all oxidation reactions (uncatalyzed and catalyzed) are also presented. It appears that CuO,, is the most efficient catalyst of those investigated. EXPERIMENTAL ApparatusThe apparatus is shown in Figure 1. At J the system ends in a Hg diffusion pump and a rotary oil pump; a liquid N2 trap and a McLeod gauge are connected to the diffusion pump. Oxidation is carried out in the quartz tube located inside the tube furnace (Phoenix Equipment Corp.). The reaction vessel containing the polymer film is first held outside the furnace in a Pyrex tube connected to the quartz tube. At time t = 0 the vessel is pushed