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Amine/epoxy stoichiometric ratio dependence of crosslinked structure and ductility in amine‐cured epoxy thermosetting resins
Author(s) -
Odagiri Nobuyuki,
Shirasu Keiichi,
Kawagoe Yoshiaki,
Kikugawa Gota,
Oya Yutaka,
Kishimoto Naoki,
Ohuchi Fumio S.,
Okabe Tomonaga
Publication year - 2021
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.50542
Subject(s) - epoxy , stoichiometry , thermosetting polymer , materials science , ultimate tensile strength , ductility (earth science) , composite material , brittleness , curing (chemistry) , elongation , amine gas treating , polymer chemistry , chemistry , organic chemistry , creep
Epoxy‐amine thermosetting resins undergo different reactions depending on the amine/epoxy stoichiometric ratio ( r ). Although many desirable properties can be achieved by varying the stoichiometric ratio, the effects of the variation on the crosslinked structure and mechanical properties and the contribution of these factors to the ductility of materials have not been fully elucidated. This study investigates the brittle‐ductile behavior of epoxies with various stoichiometric ratios and performs curing simulations using molecular dynamics (MD) to evaluate the crosslinked structures. The molecular structure is predominantly branched in low‐stoichiometric ratio samples, whereas the chain extension type structure dominates the high‐stoichiometric ratio samples. As a result, the higher‐stoichiometric ratio samples enhances the ductility of materials and the elongation at break increases form 1.4% ( r = 0.6) to 11.4% ( r = 1.4). Additionally, the tensile strength (105.4 MPa) and strain energy (7.96 J/cm 3 ) are maximum at r = 0.8 and 1.2, respectively. On the other hand, the Young's modulus is negatively impacted and it decreased from 4.2 to 2.7 GPa with increasing stoichiometric ratio.