Synthesis and properties of polyurethane/clay nanocomposites

Abstract

In this dissertation, we prepared the organoclays which can form stable suspension in polar organic solvents via treatment with chain-extended organifiers and introduced the organoclays in polyurethane/clay nanocomposites. The effect of the chemical structure of the organifiers on the properties of the organoclays such as d-spacing, ion-exchanged fraction, and suspension stability in polar organic solvents was investigated. The effects of the organoclays on the properties of the nanocomposites such as the morphology, molecular weight, glass transition temperature, barrier property, thermal stability, and tensile properties of the nanocomposites were also investigated. In chapter 2, the effect of the chemical structure of the organifiers on the properties of organoclays was investigated. When the organifiers had ester group, ion-exchanged fraction(IEF) depended on the interaction between layered silicate and polyol. There can be attractive interaction between hydrophilic PEG (poly(ethylene glycol)) and hydrophilic layered silicate, so the organifier having ester group and PEG showed higher IEF than the organifier having ester group and PTMG (poly(tetramethylene ether glycol)). However, although there was hydrophobic PTMG in the organifier having urethane group, the organifier had high values of IEF due to the formation of hydrogen bonding between the urethane groups in the organifiers and the layered silicates. The d-spacing of organoclays increased with increasing the molecular weight of organifier due to the increase of its chain length. Because the urethane groups in the organifiers could form hydrogen bonding with layered silicates, the organifier having urethane group showed high values of both IEF and d-spacing. Hydrophobic PTMG chain of the organifier tries to retain its coil-like conformation and the conformation of hydrophilic PEG chains of organifier is rather flat, so the d-spacing of the organifier having urethane group and PTMG was rapidly increase...