Higher performance polyurethane-organoclay nanocomposites
thesisposted on 20.01.2011 by Kejian Yao
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A series of polyurethane (PU)-organoclay nanocompositcs were synthcsised by swelling organically-modified layered silicate (organoclay) in a polyol with subsequent polymerisation. The techniques of wide-angle x-ray diffraction (WAXD), small-angle x-ray scattering (SAXS), transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), Fourier transform infer-red spectroscopy (FTIR), modulated differential scanning calorimetry (MDSQ, contact angle measurement and tensile test were used to investigate the effect of addition of organoclay on curing dynamics, phase structure, tensile properties, dynamical mechanical thermal analysis (DMTA), fatigue durability and surface properties of PUs. FTIR and MDSC revealed that the addition of organoclay has an important influence on curing process of PUs. With increasing organoclay, the reaction between -OH group in polyol and- NCO in isocyanate became fast. WAXD and TEM results showed that PU-organoclay nanocomposites prepared in this research were intercalated materials ones. The addition of organoclay has significant influences on the phase structure of PUs. SAXS results revealed that the long period (average thickness of soft and hard segment) decreased with increasing organoclay. Contact angle measurements showed that the organoclay can affect the surface properties of PU nanocomposites. The addition of organoclay resulted in the decrease in surface energy. AFM results revealed that the adhesion force of the surface of PU nanocomposites decreased with increasing organoclay. Tensile strength and elongation of PUs at break were improved significantly by incorporating organoclay. The tensile strength increased up to 100%, and elongation increased up to 120%. At high soft segment content, with increasing organoclay, the modulus decreased slightly, and at low soft segment content, the modulus increased with increasing organoclay. The addition of organoclay improved significantly thermal stability of PUs. Fatigue measurements uggestedt hat the fatigue durability can significantly be improved by incorporating organoclay. A nanospring concept for understanding the enhancemenht as been proposed.
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