Mechanical properties of reactive polyetherimide-modified tetrafunctional epoxy systems

• Published in: Polymer (Guilford) Vol. 270; p. 125763
• Main Authors: Chen, Hengxi, Zhu, Zewen, Patil, Dadasaheb, Bajaj, Devendra, Verghese, Nikhil, Jiang, Zhiyuan, Sue, Hung-Jue
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 27.03.2023
• Subjects: Fracture toughness; Functional oligomers; Particle bridging; Reaction-induced phase separation; Reactive polyetherimide; Tetrafunctional epoxy resin; Tetrafunctional epoxy resin; Reaction-induced phase separation; Reactive polyetherimide; Functional oligomers; Particle bridging; Fracture toughness
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2023.125763

Highly crosslinked multifunctional epoxy resins are commonly brittle. Thermoplastic toughening agents have been used to improve the fracture toughness of crosslinked epoxy resins. However, toughness improvement is limited due to poor interfacial adhesion between epoxy matrix and thermoplastic toughener. Furthermore, it is desired that toughness improvements should not come at the expense of other properties, including modulus, thermal properties and processability. In this work, amine functionalized reactive polyetherimide (rPEI) having two different molecular weights and loading levels were incorporated in tetraglycidyl-4, 4′-diaminodiphenyl methane (TGDDM) epoxy resin to study the structure-property relationship, including effects of reaction-induced phase separation on fracture toughness. Results demonstrate that the phase morphologies of rPEI in an epoxy resin can be drastically affected by the functionality, molecular weight and loading levels of rPEI. The mode-I fracture toughness (KIC) of rPEI-toughened epoxy is increased by up to 140% versus untoughened epoxy control. An investigation into the fracture mechanisms of rPEI-toughened TGDDM epoxy showed evidence of rPEI particle bridging as one of the key mechanisms of toughening. Our work further demonstrated that the rPEI-toughened TGDDM epoxy maintained both high modulus and high Tg, rendering it suitable for a wide range of applications. [Display omitted] •High performance thermosets based on TGDDM epoxy can be significantly toughened using telechelic rPEI with –NH2 end-group.•The –NH2 functionality on PEI telechelics can participate in epoxy crosslinking process to achieve strong interfacial adhesion.•Different molecular weights of rPEI can influence miscibility and phase morphology in epoxy.