Imidazolium ionic liquids as fracture toughening agents in DGEBA-TETA epoxy resin

• Published in: Polymer testing 2020-07, Vol.87, p.106556, Article 106556
• Main Authors: Fonseca, E., Demétrio da Silva, V., Klitzke, J.S., Schrekker, H.S., Amico, S.C.
• Format: Article
• Language: English
• Subjects: Bisphenol A; Crosslink density; Curing agent; Imidazolium salt
• ISSN: 0142-9418; 1873-2348
• DOI: 10.1016/j.polymertesting.2020.106556

Although epoxy resins are used in a broad variety of applications due to their good mechanical and thermal properties, their low fracture toughness is a limitation, exhibiting brittle behavior. This study explored the potential use of imidazolium ionic liquids (IL) as toughening agents for epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) with triethylenetetramine (TETA) as curing agent. Fracture toughness was evaluated for DGEBA-TETA epoxy resins with eleven imidazolium IL and the best results were found for the IL with the chloride anion and the shortest N-alkyl side chain, C4MImCl. The use of 1.0 phr of C4MImCl lead to the reduction of the crosslink density of the post-cured resin, resulting in the increase of 25.5% in stress intensity factor and 8.2% in tensile strength with no significant loss in other mechanical properties. •The highest fracture toughness of DGEBA-TETA epoxy resin was achieved with the ionic liquid additive 1-n-butyl-3-methylimidazolium chloride.•No significant losses in other mechanical properties occurred with the addition of a low amount of 1-n-butyl-3-methylimidazolium chloride.•1-n-Butyl-3-methylimidazolium chloride reduced the reaction energy for epoxy resin curing, and the post curing cross-linking density.•An inverse relationship between cross-linking density and fracture toughness was found.