Synthesis and properties of elastomer-modified epoxy-methacrylate sequential interpenetrating networks

摘要

The structure and properties of copolymerized sequential-interpenetrating networks (SeqIPNs) synthesized from amine-cured epoxies and free-radical polymer-ized dimethacrylates were examined. Materials were synthesized with and without the incorporation of an epoxy-terminated butadiene—nitrile reactive elastomer. Synthesis proceeded through full thermal cure of the epoxy-amine network, followed by polymer-ization of the methacrylate network. The methacrylate reactions were free-radically induced using thermal (peroxide-initiated) or photochemical [electron-beam (e-beam)l techniques. Fourier transform infrared spectroscopy was used to monitor epoxy-amine step-growth polymerization in situ and to measure final cure conversion of methacry-lates. Structural examination of the IPNs using atomic force microscopy and scanning electron microscopy revealed microphase separation in the neat-SeqlPN materials and macroscopic phase separation of rubber-rich domains for elastomer-modified networks. Dynamic mechanical analysis of the SeqIPN determined that the properties of the network are strongly dependent on the cure conditions. Furthermore, the viscoelastic behavior of the e-beam-cured SeqIPN could be adequately described by the Williams-Landel-Ferry and Kohrausch-Willams-Watts equations, presumably because of a strong coupling between the epoxy-amine and methacrylate networks.