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|標題:||The Study of Interfacial Modification on Physical Properties of Polystyrene/Montomrillonite Nanocomposites
|關鍵字:||Montmorillonite;蒙脫土;Styrene;Methyl methacrylate;Surface Polymerization;Bulk Polymerization;Adsolubilization;Admicelle;CTAB;苯乙烯;甲基丙烯酸甲酯;表面聚合;塊狀聚合;溶化;吸附微胞;CTAB||出版社:||化學工程學系||摘要:||
This thesis is aimed at surface modification of Montmorillonite (MMT) by coating styrene-acrylate copolymer via surface polymerization. We tried improve the adhesion between MMT and styrene-acrylate copolymer by the interaction between carbonyl polar group of acrylate and polar of MMT. These modified MMT platlets were easily dispersed and swollen in styrene monomer. Polystyrene-clay nanocomposites were prepared through bulk polymerization .
Cetyltrimethyl ammonium bromide (CTAB) was used to perform the ion-exchange with Na+ on MMT surface and to form admicelle on MMT surface. The adsolubilization of styrene and methyl methacrylate into CTAB bilayers (admicelles) adsorbed on MMT was measured by HPLC. Results showed that the adsolubilization constant of styrene was 800M-1 which was nearly constant despite varying equilibrium concentration of styrene in the aqueous phase. While the adsolubilization constant of methyl methacrylate decreased with increasing equilibrium concentration . In the mixed monomer system , adsolubilization constants for styrene and methyl methacrylate were all decreased with increasing monomer equilibrium concentration in the aqueous phase. Samples after surface polymerization were analyzed with respect to the d-spacing by X-ray diffraction (XRD) and glass transition temperature by DSC. The molecular weight of copolymer formed on MMT was measured with GPC/light scattering. The PS/MMT nanocomposites contained 1 wt% and 3 wt% MMT in the polystyrene matrix were prepared. X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated the exfoliation of MMT in polystyrene. Some local areas appeared to contain a bundle of 2-6 parallel silicate layers with basal spacing equals to 3-4 nm that is consistent with the XRD analysis. Also , these nanocomposites were analyzed by DMA for measuring storage modulus (E'') , loss modulus (E") and loss factor (tanδ). The storage modulus of nanocomposites containing 3 wt% MMT modfied by styrene-acrylate copolymer was 1.4 times that of polystyrene without clay. For MMT modified by poly(styrene-methyl methacrylate) copolymer, storage modulus and loss modulus were 1.2 times that of MMT modified by polystyrene. In this research, we have prepared PS/MMT nanocomposites with good mechanical properties through surface copolymerization of styrene and acrylate on MMT to enhance the interfacial bonding between polystyrene and MMT.
本研究利用表面聚合 (Surface Polymerization) 方式，在蒙脫土表面聚合披覆一層聚苯乙烯-壓克力高分子共聚合物，藉由壓克力之極性碳醯基與蒙脫土互相作用，增強蒙脫土表面與共聚合物的黏著力，再將此改質之蒙脫土加至苯乙烯單體中膨潤分散，並經塊狀聚合形成聚苯乙烯/蒙脫土奈米複合材料。
本實驗使用四級銨界面活性劑Cetyltrimethyl Ammonium Bromide (CTAB) 與蒙脫土的鈉離子進行離子交換，形成吸附微胞結構，再加入苯乙烯及甲基丙烯酸甲酯 (MMA) 進行溶化，結果顯示苯乙烯的溶化平衡常數為一常數值800M-1，不會隨著苯乙烯平衡濃度而改變，當MMA的平衡濃度增加時，MMA的溶化平衡常數逐漸減少，在混合單體加入系統中，當苯乙烯及MMA的平衡濃度增加時，苯乙烯及MMA的溶化平衡常均減少。將已溶化單體進行表面聚合形成親油化蒙脫土，以DSC、XRD及光散射分析蒙脫土表面共聚合物的玻璃轉移溫度、層間距離分佈及分子量分佈。在苯乙烯中添加1 wt%及3 wt%蒙脫土進行塊狀聚合形成Polystyrene/Clay奈米複合材料，由XRD及TEM觀察蒙脫土在聚苯乙烯中成剝離狀，但在某些區域仍有2-6片蒙脫土成束在一起層間距離仍維持3-4 nm。添加3 wt%蒙脫土經聚苯乙烯-壓克力改質的聚苯乙烯/蒙脫土奈米複合材料的儲存模數 (E'') 比純聚苯乙烯高出1.4倍，另外，蒙脫土經由聚苯乙烯-甲基丙烯酸甲酯共聚合物改質的抗折模數 (E''及E") 比蒙脫土經純聚苯乙烯改質高出1.2倍。
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