Course of degradation and build‐up reactions in isotactic polypropylene during peroxide decomposition

In the investigation of the course of degradation and build‐up reactions during the decomposition of the tert‐butyl perbenzoate (TBPB) (at eight different concentrations) in isotactic polypropylene (iPP), it was found that, at the beginning of the peroxide decomposition at all investigated peroxide concentrations from 4.62–200 mmol/kg iPP, the degradation reactions of iPP prevailed. At the TBPB concentration of ≤37.0 mmol/kg iPP during the whole period of peroxide decomposition, degradation reactions leading to a lower of molecular mass of PP prevailed. But at higher peroxide concentrations of TBPB ≥74.4 mmol/kg iPP and at the later stage of peroxide decomposition, a predominance of the build‐up reactions, that is, an increase the molecular mass, was observed. The degradation and build‐up reactions were determined from the measurements of the melting‐flow indexes of the peroxide‐treated iPP samples. The reaction mechanism of the degradation and build‐up reactions in iPP is discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 886–893, 2000