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Study of the curing of a polyurethane using the Weissenberg Rheogoniometer
Author(s) -
Hartley Mark D.,
Williams H. Leverne
Publication year - 1981
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.760210305
Subject(s) - materials science , branching (polymer chemistry) , polybutadiene , dispersity , dynamic mechanical analysis , curing (chemistry) , gel permeation chromatography , shear modulus , viscoelasticity , molar mass distribution , polyurethane , isocyanate , polymer , polymer chemistry , dynamic modulus , shear rate , modulus , composite material , swelling , analytical chemistry (journal) , viscosity , chromatography , chemistry , copolymer
Gel Permeation chromatography (GPC) yielded high values for branching frequency. Low polymers persisting long into the reaction and impurities resulted in almost constant number average molecular weights and steeply rising polydispersity. The percent insolubles was low and passed through a maximum attributed to a 1,2,3‐propantriol/isocyanate reaction product which was insoluble and became solubilized by the addition of polybutadiene. The dynamic viscosities of the products rose with conversion. When studied over various shear rates, the curves could be extrapolated to zero shear values. The relationship between zero shear viscosity and molecular weight yielded a slope of 3.5 for linear samples and a lightly branched sample prepared using 1,6‐hexamethylene diisocyanate. The lightly branched samples made using 2,4‐toluene diisocyanate yielded slopes less than 3.5. The highly branched samples yielded slopes well above 3.5. The moduli increased rapidly with reaction time and then levelled off. In the absence of 1,2,3‐propantriol, the loss modulus surpassed the storage modulus. When 1,2,3‐propantriol was added, the moduli increased more rapidly, levelled off at higher values, and the storage modulus exceeded the loss modulus. Studies of the swelling of the final product showed that these measurements yielded abnormally high values for the molecular weight between crosslinks; evidence of poor network formation.