Mechanical and Thermal Properties of Epoxy Resins Modified by a Novel Thermoplastic-polyimide

In this paper, a novel polyimide with trifluoromethyl group (PIS) was synthesized successfully and used to improve the toughness of epoxy resins. Five modified epoxy resins (5, 7.5, 10, 12.5 and 15 wt%) were prepared and investigated, respectively. The structure, thermal properties, tensile properties, viscoelastic properties, toughness and morphology of modified epoxy resins were studied by Fourier Transform Infrared Spectroscopy (FT-IR), thermogravimetric analysis (TGA), Instron 5967, Dynamic Mechanical Analysis (DMA), and Scanning Electron Microscopy (SEM). The results showed that the epoxy resins modified with PIS exhibited good thermal stability which the glass transition temperatures increased from 135.9 °C to 146.4 °C. Tensile strength of modified epoxy resins increased from 40.4 MPa to 92.3 MPa. The KIC values increased from 0.86 MPa·m1/2 to 1.56 MPa·m1/2 indicated that the toughness enhancement was markedly. The fracture modes also were examined by SEM images and exhibited the fracture mode changed from the brittle one to ductile fracture with varied weight of the novel trifluoromethyl-polyimide.