A commercial high‐impact polypropylene (hiPP) was fractionated by temperature‐gradient elution fractionation into nine fractions. All fractions were studied using Fourier transform infrared spectroscopy and differential scanning calorimetry. The amount of ethylene in the fractions was also determined. The results demonstrate that the ethylene–propylene statistical copolymer (or ethylene–propylene rubber, EPR) content in this hiPP is rather low and the amounts of ethylene–propylene segmented copolymer and ethylene–propylene block copolymer (that act as adhesive and compatibilizer between elastomeric phase and matrix, respectively) are negligible. Furthermore, the morphology of the resin was studied using scanning electron microscopy observations of microtome‐cut original and etched samples, which reveals that EPR particles are too large and their distribution inside the matrix is not uniform. Copyright © 2010 Society of Chemical Industry

Infrared spectroscopy is a powerful technique for studying the microstructure and determining the short-chain branch distribution of polyethylene. In this work, the types and amounts of short-chain branches in low-density polyethylene were investigated with Fourier transform infrared spectroscopy, and a new and simple method for the determination of butyl short branches was discovered. The amount of each unsaturated species in low-density polyethylene was also determined with Fourier transform infrared after the bromination of samples. Furthermore, the resin was fractionated by preparative temperature rising elution fractionation, and the branch distribution and melting endotherm of each fraction were analyzed with attenuated total reflectance/Fourier transform infrared and differential scanning calorimetry.

Four different grades of commercial, highimpact polypropylene (hiPP) were fractionated by temperature-gradient extraction fractionation, and the chain structure and melting behavior of the fractions were studied by Fourier transform infrared spectroscopy and differential scanning calorimetry. Furthermore, the morphology of the disperse phase in the resins was characterized by scanning electron microscopy of the microtome-cut etched and original samples. The results show that there was a strong relation between the chain structure, content, and distribution of the dispersed phase and the mechanical properties of hiPP. These parameters of the elastomeric phase are really critical in reaching the best rigidity-impact balance in hiPP.