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Emergence of time‐dependent material properties in chain extended polyureas
Author(s) -
Iqbal N.,
Kumar D.,
Roy P. K.
Publication year - 2018
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.46730
Subject(s) - polyurea , curing (chemistry) , materials science , coating , isocyanate , polymer , stress relaxation , composite material , amine gas treating , polymer chemistry , chemical engineering , polyurethane , chemistry , organic chemistry , creep , engineering
In this article, we report the emergence of material properties of polyurea over a finite time frame. Due to the rapid isocyanate–amine reaction, polyurea formation occurs practically instantaneously. Despite being an “instant‐curing” system, the material properties of polyurea evolve substantially with time: phenomenon, which warrants a methodical study. The curing process of polyurea formulations, containing both aliphatic and aromatic chain extender, has been studied systematically with an aim to gain insight into the time frame associated with its curing and subsequent stress relaxation. Formulations containing aromatic chain extender mandated relatively lesser time to “gel,” but the complete disappearance of NCO absorbance mandated much longer periods ∼7 h. Interestingly, in all the formulations, mechanical properties improved with time and reached their optimal properties over a period of 15 days. This improvement has been attributed to several processes simultaneously occurring within the matrix; the foremost being the relaxation of internal stresses which tend to buildup in the polymer during the spray coating process. In addition, significant changes occur in the internal morphology of segmented polymers, which in turn is a result of H‐bond rearrangement.