Synthesis and Characterization of Organo-montmorillonite/Polyurethane Nanocomposites

• Main Authors: Yun. I. Tien, 田運宜
• Other Authors: K. H. Wei
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/31166888700289741244

博士 === 國立交通大學 === 材料科學與工程系 === 89 === Synthesis and Characterization of Organo-montmorillonite/Polyurethane Nanocomposites Student : Yun-I Tien Advisor : Dr. Kung-Hwa Wei Department of Material Science and Engineering National Chiao Tung University Abstract Two kinds of polyurethane nanoocmposites were synthesized and characterized. In the first part of the experiment, the montmorillonite modified by the benzidine (BZD) was dispersed in the polyurethane containing different hard segment ratios. It was found that the dispersion of silicate became poorer with the increasing amount of BZD-Mont and hard segment, evidenced by the X-ray and TEM results. Hydrogen bonding in the hard segments of the nanocomposites decreased with the increasing BZD-Mont contents regardless of the hard segment ratios, but reached plateau values at 5 wt % BZD-Mont concentration. The maximal reductions of the hydrogen bonding in the polyurethane nanocomposites ranged from 20 to 37 %, depending on the hard segment ratios as compared to that in the pure polyurethane. The maximal strength and the elongation at break of the polyurethane nanocomposites increased dramatically as compared to that of pristine polyurethane, with the maximal values occurred at 1 wt % BZD-Mont concentration. As concerned as the thermal characteristics of BZD-Mont/PU, the presence of less than 5 wt % layered silicates from BZD-Mont can result in hard segments having thermally more stable long-range-order and higher melting temperature, but a loss of crystallinity of hard segment in polyurethane. Additionally, the degradation temperature of the polyurethane nanocomposite was 40 oC higher than that of pure polyurethane. In the second part of the experiment, novel intercalated and exfoliated layered silicates/polyurethane were synthesized by using reactive swelling agent-modified-silicates as pseudo chain extenders for polyurethane prepolymer. The dispersion of layered silicates in polyurethane was found to be transformed from an intercalated to an exfoliated structure when the number of hydroxyl groups of the swelling agent increased as evidenced from the TEM and X-ray analyses. The improved morphology of the nanocomposites resulted in a substantial increase in their mechanical properties, despite variations in the molecular weight and in the extent of hydrogen bonding in the hard segment phase of polyurethane. In particular, a 34 % increase in Young’s modulus, a 1.6 times increase in the maximum stress and a 1.2 times increase in the elongation at break occurred in the nanocomposite of polyurethane containing 1 wt % tri-hydroxyl groups swelling agent modified silicates as compared to that of pristine polyurethane. Moreover, the heat resistance of polyurethane was enhanced by the nano-sized silicates around the hard segments, evidenced by the 39 oC increase in degradation temperature and 17 kJ/mole increase in the activation energy at 10 % conversion as compared with those of pristine polyurethane.