Enhanced mechanical and thermal properties of polyurethane-imide foams with the addition of expended vermiculite

Polyurethane-imide (PUI) foams, in combination with the mechanical performance of polyurethane and flame retardancy of polyimide, were prepared by polyimide prepolymer method. Expended vermiculite (EV), with a wider layer spacing than vermiculite, was used as the filler to further enhance the mechanical and thermal properties of the PUI foams. The effect of filler content on the morphology of foams was also investigated. The results showed that the mean cell diameter of foams became smaller and the cell size distribution was more uniform at low filler content. The addition of EV resulted in a substantial increase in thermal stability. The compression strength increased from 0.024 to 0.065 MPa with an increase in EV content from 0% to 9.6%. The limited oxygen index values increased from 24% to 30.8% with an increase in filler content from 0% to 9.6%. Hence, PUI foams could significantly enlarge its application range with the addition of EV.