Structural analysis of poly(ethylene terephthalate) modified by polypropylene‐graft‐maleic anhydride from rheological data

Abstract During some investigations on compatibilizing poly(ethylene terephthalate) (PET) blends by maleic anhydride–grafted polyolefins (PO‐g‐MA), the reaction between PET and PO‐g‐MA and the formation of PO‐g‐PET were proposed. However, the effect of PO‐g‐MA on the rheological properties of PET has not been the aim of any specific study. In our study, polypropylene (PP)‐g‐MA was melt reacted with PET, and the effects of its content and grafting degree on the intrinsic viscosity and linear viscoelastic properties of PET were investigated. The results reveal that the addition of PP‐g‐MA leads to increasing intrinsic viscosity, which confirms the reaction between PP‐g‐MA and PET. Rheological measurements suggest that the addition of PP‐g‐MA improves the elastic behavior and increases the complex viscosity of PET. No shear thinning behavior was observed for any samples, indicating that branching is not widespread. The increase in PP‐g‐MA content or grafting degree leads to increases in the intrinsic and complex viscosities and improves the elastic behavior. Furthermore, we reported the unusual observation of an increasing viscosity with frequency in modified sa"mples due to the transesterification phenomenon. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 46896.