Investigation of the Hydrogen-Bonding Structure and Miscibility for PU/EP IPN Nanocomposites by PALS

Effects of hydrogen bonding on the free volume and miscibility were first investigated for polyurethane/epoxy resin (PU/EP) interpenetrating polymer network (IPN) nanocomposites by positron annihilation lifetime spectroscopy (PALS), Fourier transform infrared spectroscopy (FTIR), and dynamic mechanical analysis (DMA). Infrared spectroscopy suggested that the strengths of two kinds of hydrogen-bonding interactions including both between carbonyl group and N−H group and the other between urethane group in PU and silicate layers depended strongly on the dispersed state of the layered montmorillonite (MMT) in the matrix. We found that the stronger the hydrogen-bonding interaction, the higher the average chain packing efficiency and the smaller the free volume hole size, the better the miscibility. On the other hand, from the analyses of distributions of the free volume and the loss factor, it is very interesting that the large differences between the exfoliated structure and the intercalated structure of MMT were observed.