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Network formation in polyurethanes due to allophanate and biuret formation: Gel fraction and equilibrium modulus
Author(s) -
Dušek Karel,
Špírková Miléna,
Ilavský Michal
Publication year - 1991
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19910450112
Subject(s) - biuret test , polymer chemistry , isocyanate , macromolecule , fraction (chemistry) , thermodynamics , branching (polymer chemistry) , modulus , materials science , elastic modulus , chemistry , composite material , organic chemistry , polyurethane , physics , biochemistry , urea
Gel fraction and equilibrium elastic modulus of networks formed from α, ω‐dihydroxypoly(oxypropylene) and bis(4‐isocyanatophenyl)methane (MDI) as a result of side reactions were compared with theoretical predictions based on the theory of branching processes (Macromolecules, 23, 1774 (1990)). If isocyanate is in excess, trifunctional allophanate and biuret groups are formed. The experimental sol fraction can be correlated with theoretical predictions. The resulting networks are rather weak and the measured equilibrium modulus can be correlated with the theoretical values calculated from the concentration of elastically active network chains if the value of the front factor is close to that of a phantom network without a trapped entanglements contribution.