Amine/epoxy stoichiometric ratio dependence of crosslinked structure and ductility in amine-cured epoxy thermosetting resins

Nobuyuki Odagiri, Keiichi Shirasu, Yoshiaki Kawagoe, Gota Kikugawa, Yutaka Oya, Naoki Kishimoto, Fumio S. Ohuchi, Tomonaga Okabe

Research output: Contribution to journalArticlepeer-review

Abstract

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/cm3) 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.

Original languageEnglish
Article number50542
JournalJournal of Applied Polymer Science
Volume138
Issue number23
DOIs
Publication statusAccepted/In press - 2021

Keywords

  • crosslinking
  • mechanical properties
  • structure-property relationships
  • thermosets

ASJC Scopus subject areas

  • Chemistry(all)
  • Surfaces, Coatings and Films
  • Polymers and Plastics
  • Materials Chemistry

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