Oxidation of polypropylene in benzene solution

The oxidation of both amorphous and crystalline polypropylene in benzene solution was studied at 100–130°C. tert‐Butyl peroxide was used as an initiator. The kinetic behavior of the amorphous and crystalline forms differs slightly; the oxidation rate of the amorphous type is slower for a given polymer and initiator concentration. The oxidation rate of solutions of the crystalline form can be simply described by the expression: R0 = 1.87 × 1013 exp {−29,000/RT} [t‐Bu2O2]0.58[polypropylene]0.73, mole/l.‐min. Product analyses of the oxidized solutions are incomplete, but the results do show that only ∼40% of the absorbed oxygen is present as hydroperoxide. Further, much of the hydroperoxide is present in low molecular weight polar fragments which are acetone‐soluble. These results show that oxidized polypropylene cannot be regarded simply as “polypropylene hydroperoxide” with repeating hydroperoxide groups attached to the polymer chain in 1,3,5… (tertiary) positions.