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Chemorheological characterization of thermosetting polyurethane formulations containing different chain extender contents
Author(s) -
Haddadi Hamed,
Nazockdast Ehssan,
Ghalei Behnam
Publication year - 2008
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.21229
Subject(s) - extender , materials science , thermosetting polymer , gel point , viscoelasticity , polyurethane , composite material , polymer chemistry , chemical engineering , rheology , engineering
Chemorheological analyses of thermosetting polyurethane (PU) formulations containing various amounts of chain extender were carried out. In the first part of the present research, effect of chain extender content on the gel time and its dependency with temperature were investigated for PU formulations. Gelation temperature ( T gel ) and gel time ( t gel ) of reactive systems were determined using temperature sweep and time test measurements under dynamic linear viscoelastic deformations. The results of temperature sweep experiments for the samples containing various chain extender weight percents showed that the gelation temperature declined by increasing the chain extender content of PU formulations. The analysis made on gel times determined in a wide temperature range indicated that the activation energy for the gelation process declined and 1/ t gel , as a measure of the rate of gelation process, dramatically increased with increasing chain extender concentration. In the second part of this study, calculation of viscoelastic characteristics at the gel point was performed. The results showed that the relaxation exponent ( n ) declined with increasing chain extender, while the fractal dimension increased. These results confirmed that the gel structures became more elastic and with a tighter structure by increasing the chain extender concentration in PU formulations. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers