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The rheology of polypropylene—the influence of molecular weight distribution on melt elasticity
Author(s) -
Petraglia G.,
Coen A.
Publication year - 1970
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760100205
Subject(s) - dispersity , tacticity , rheology , polypropylene , molar mass distribution , materials science , branching (polymer chemistry) , melt flow index , elasticity (physics) , fractionation , polymer chemistry , swelling , thermodynamics , composite material , polymerization , chemistry , polymer , chromatography , copolymer , physics
The structure of isotactic polypropylene, obtained by means of Ziegler‐Natta catalysis, can be characterized only by molecular weight distribution. The mechanism of stereospecific catalysis eliminates other variables, i.e., short and long branching. In this case it is possible to develop a rheological study dependent only by polydispersity. The spectrum of relaxation times of five samples of polypropylene have been calculated from swelling measurement in the molten state and from flow master curves. The molecular weight distribution of the samples has been calculated by means of the relaxation spectrum, as suggested by Ferry. This information has been compared with that obtained by a fractionation method. There is a good agreement between the calculated and measured polydispersity curves.