Preparation and properties of polyurethane-modified epoxy cured in different simulated gravity environments

Great attention has been paid to the composites with interpenetrating polymer networks (IPNs) because of their special performance. However, the influence of sedimentation and convection from different gravity environments on the formation of IPNs and the properties of IPNs blends has received little attention. To understand their influence, environments with different gravity accelerations of 0g, 1g, and 2g were simulated with a superconducting magnet, and tests, including differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), coefficient of thermal expansion (CTE), scanning electron microscopy, and three-point bending, of the IPNs blends cured in different gravity environments were conducted and analyzed. Fourier transform infrared spectroscopy, DSC, and DMA proved the formation of IPNs during the reaction between the polyurethane prepolymer (PUP) and epoxy resin (E51). The curves of DSC also certified the differences in the curing degree between the different parts along the direction of gravity of a sample. With the increase of mass fraction of PUP, the change trends of the storage modulus presented a linear decrease when samples cured in microgravity environment, but presented a parabolic trend when samples were cured in terrestrial environment. The damping properties of samples cured in simulated microgravity environments are better than those cured in terrestrial environment. With the increase in the simulated acceleration of gravity, the diameter of dispersed phase in a sea-island structure increased, but their number decreased and the bending stress and CTE of the IPN blends all decreased. These results show the formation of IPNs was affected by different gravity values, and the thermal and mechanical properties of the IPN composites were influenced by the changed IPN components. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42063.