Fractionation and characterization of an ethylene–propylene copolymer produced with a MgCl2/SiO2/TiCl4/diester-type ziegler–natta catalyst
✍ Scribed by Qi Dong; Zhi-Qiang Fan; Zhi-Sheng Fu; Jun-Ting Xu
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 252 KB
- Volume
- 107
- Category
- Article
- ISSN
- 0021-8995
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✦ Synopsis
Abstract
An ethylene–propylene copolymer synthesized with a Ziegler–Natta catalyst was fractionated by a combination of dissolution/precipitation and temperature‐gradient extraction fractionation. The fractions were characterized with ^13^C‐NMR, differential scanning calorimetry, and wide‐angle X‐ray diffraction. The fractionation was carried out mainly with respect to the content of ethylene, but the crystallizable propylene sequences could also exert an influence on the fractionation. The copolymer contained a series of components with wide variations in the compositions. With an increase in the ethylene content, the structure of the fractions became blockier and blockier, and the fraction extracted at 111°C had the blockiest structure. A further increase in the ethylene content led to a decrease in the length and number of the propylene sequences. Differential scanning calorimetry results showed that the composition distribution in single fractions was not homogeneous, and multiple melting peaks were observed. Wide‐angle X‐ray diffraction results revealed both polyethylene and polypropylene crystals in most of the fractions. Short propylene sequences could be included in the polyethylene crystals, and short ethylene sequences could also be incorporated into the polypropylene crystals. The incorporation of propylene sequences into polyethylene crystals strongly depended on the sequence distribution and crystallization conditions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008