有機蒙特納石/聚胺基甲酸酯奈米複合材料之製備與分析

Abstract

為了改善聚胺基甲酸酯（PU）之機械及耐熱性質，本論文將蒙特納石的矽酸鹽層以奈米尺寸分散在PU中，製備PU奈米複合材料；研究可分為兩大部分：第一部分將有機蒙特納石（BZD-Mont）經摻合分散在硬鏈段含量不同之PU中（PU39，PU50，PU63），探討矽酸鹽在不同硬鏈段含量PU中的分散情況及其性質變化；結果顯示矽酸鹽於PU內分散之均勻性隨硬鏈段或蒙特納石含量增加而下降。另外，因為板狀矽酸鹽的阻隔減低了硬鏈段間氫鍵程度，使得PU39、PU50和PU63三個系統中之硬鏈段氫鍵連結指數分別下滑19.7 %、34.1 %和36.5 %。而在機械性質部分，得知奈米級矽酸鹽可補強PU；於PU39系統中，其楊氏模數、最大拉伸應力和斷裂伸長率可分別增加至25.97 MPa、7.94 MPa 和610 %。關於該PU奈米複合材料之熱性質，則發現矽酸鹽並不影響軟鏈段相玻璃轉移點與硬鏈段相之熔點，但會減低硬鏈段相中微結晶的程度，於此同時，長範圍規則排列之硬鏈段數量變多，使得△H2可增加17 J/g；另外因為矽酸鹽會限制硬鏈段分子的運動，所以其T2隨矽酸鹽含量增加至多提升9 oC。而耐熱性則因奈米矽酸鹽保護了PU硬鏈段分子獲得34 oC改善。 第二部分利用膨潤劑製備出不同反應性的有機蒙特納石（1OH-Mont，2OH-Mont，3OH-Mont），並將其當作仿鏈延伸劑連結PU39預聚合體，探討有機蒙特納石反應性高低與矽酸鹽層分散形態間的關係；結果發現矽酸鹽於PU39中之分佈隨膨潤劑羥基數目增加或矽酸鹽含量減少而愈顯均勻，尤以3OH-Mont/PU39不規則排列的矽酸鹽形態最為特別。再則，因為該反應型有機蒙特納石扮演鏈延伸劑之角色，所以反應性較低者會阻礙預聚合體的鏈延伸反應，導致1OH-Mont/PU39中PU39分子量下降50 %。至於硬鏈段間氫鍵程度則同樣因矽酸鹽阻隔而減低，且此效應隨蒙特納石含量增加愈為顯著，其最低值較純PU39下降12 %。在PU39奈米複合材料機械性質的部分，矽酸鹽層不規則排列之奈米矽酸鹽可更有效補強PU39；以1wt % 3OH-Mont/PU39為例，楊氏模數、最大拉伸應力和斷裂伸長率分別上升至28.03 MPa、23.62 MPa和1167 %。最後，分析其軟、硬鏈段相玻璃轉移過程，推測矽酸鹽層藉氫鍵或膨潤劑連結而分佈在PU39中的硬鏈段相，進而保護硬鏈段分子延遲其裂解，使得PU39奈米複合材料之耐熱溫度和裂解活化能最多較純PU39提高40 oC和17 kJ/mole。

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.