Solid-state hydroxylation of polypropylene

The solid-state hydroxylation of polypropylene (PP) in water solution was investigated as a simple and attractive way for the surface hydroxylation of PP. The functionalization was initiated by potassium persulfate (K2S2O8) under inert atmosphere. The effect of various reaction parameters and surfactants on the concentration of -OH group bonded on PP backbone ([OH]PP) and the extent of collateral reactions was discussed. The increase of [OH]PP with the increase of initial concentration of K2S2O8 ([K2S2O8]0) was proved by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). β-scission and oxidative degradation of PP was detected with respect to the change of rheological behavior, differential scanning calorimetry (DSC) and FTIR. On the other hand, inverse collateral reaction leading to the increase of molar mass were evidenced at prolonged reaction period. Surface hydroxylation was detected mainly in the amorphous phase, however at prolonged reaction period the reaction occurred even in the crystalline phase.