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Polyurethane tri‐block copolymers—Synthesis, mechanical, elastic, and rheological properties
Author(s) -
Arun Araichimani,
Baack Kasper K.J.,
Gaymans Reinoud J.
Publication year - 2010
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.21579
Subject(s) - materials science , copolymer , crystallinity , polyurethane , composite material , polymer chemistry , dynamic mechanical analysis , differential scanning calorimetry , polymer , rheology , thermodynamics , physics
A series of polyurethane tri‐block copolymers were synthesized by reacting a 4,4′‐methylenebis(phenyl isocyanate) (MDI)‐endcapped poly(tetramethylene oxide) (PTMO, M n = 2,000 g/mol) with a monoamine‐diamide (6T6m) hard segment (HS). The concentration of the HS in the copolymer was varied between 9 and 33 wt % by changing the length of the soft mid‐block segment. The structure of the copolymers was analyzed by nuclear magnetic resonance, the amide crystallinity was investigated by Fourier transform infra‐red and the thermal properties were studied by differential scanning calorimetry. The mechanical and elastic properties of the tri‐block copolymer were subsequently explored by dynamic mechanical analysis, compression set and tensile experiments, and the melt rheological behavior was studied by a parallel plate method. The amide end groups displayed a high crystallinity and the modulus of the tri‐block copolymers was relatively high. The fracture strain increased strongly with the molecular weight and the copolymers demonstrated a ductile fracture behavior for molecular weights above 6000 g/mol. Good compression set values were obtained for the tri‐block copolymers despite their low molecular weight. In the molten state, the tri‐block polymers displayed a gelling effect at low frequencies, which was believed to be a result of a clustering of the end‐segments. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers