Isocyanate modified fumed silica and its effects on the mechanical properties of casting polyurethane elastomer

In order to improve the molding fluidity of fumed silica (FS)/cast polyurethane (PU) system, in the process of preparing prepolymer, the fumed silica (FS) was modified by 2, 4-toluene diisocyanate (TDI) to obtain TDI modified silica (NCO@FS), and TDI modified silica/reinforced pouring polyurethane (NCO@FS/PU) elastomer composite material was prepared by in-situ polymerization. NCO@FS and FS were characterized by fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle testing. The results show that the active hydroxyl groups on the surface of FS react with the − NCO groups of TDI to form urethane groups aminoester group (− NHCOO), which improves the interfacial compatibility and interfacial bonding between silica and casting polyurethane. When the mass fraction of NCO@FS in the composite material is 1.5wt%, the tensile and tearing strengths of the NCO@FS/PU composite material are 57 MPa and 110.5 kN/m, respectively, which are 31.6% and 23.6% higher than that of pure casting PU. The glass transition temperature dropped from 3.4°C to –11.2°C, and the loss factor tanδ dropped from 0.59 to 0.46. TDI modified fumed silica is suitable for preparing silica-reinforced cast polyurethane composites. © 2023 Beijing University of Aeronautics and Astronautics (BUAA). All rights reserved.