Synthesis of Epoxy and Block Oligomer Modified Clay Nanocomposite
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Synthesis of Epoxy and Block Oligomer Modified Clay Nanocomposite Kang Hung Chen and Sze Ming Yang* Department of Chemical and Material Engineering, National Central University, Chung-Li, Taiwan 320. *To whom all correspondence should be addressed. ABSTRACT Acrylic triblock (AxMyBz) and diblock (MyBz) oligomers containing methyl methacrylate (MMA, M), methacrylic acid (MAA, A) and dimethylaminoethyl methacrylate (DMAEMA, B) groups are intercalated into the layers of montmorillonite. The results indicate that the block oligomer lay flatly between the clay layers. ICP analyses of Na+ content indicate no unexchanged sodium ions are left in the intercalated clay. Nanocomposites of epoxy and clay modified with block oligomers were synthesized. Glass transition temperature (Tg) of the nanocomposite is 129.6oC (M18B2424+ modified clay) compared to 84.1oC for the physical mixture of epoxy and unmodified clay. Tg increases with decreasing amount of modified clay. When modified clay content are below 2 phr, Tg higher than 131.7 oC can be obtained. Water resistance and light transmittance of the nanocomposite is also improved over composite of epoxy and unmodified clay. INTRODUCTION Clay or other inorganic materials have been added into polymer as fillers in order to improve the properties of the polymer such as dimensional stability, conductivity, mechanical, thermal and other potential properties.[1,2]. The intercalation of modified ions into the layers affects the exfoilation of the clay layer in the composite. Lan and Pinnavaia reported the enlargement of dspacing to 18.0 Å by intercalation of onium ions [3,4]. The largest d-spacing of modified montmorillonite reaches 20.27 Å [5]. It is interesting to understand the intercalation of the clay such as montmorillonite. Acrylic block oligomers were synthesized in different chain length, hydrophobicity, sequence and charge density. Onium ions such as [H3N(CH2)n-1COOH]+, [H3N(CH2)n-1CH3]+, [H3N(CH2)nNH2]+ and [H3N(CH2)nNH3]2+ were reported to be intercalated into the clay layers. When n>17, the compounds become too hydrophobic to be soluble enough in water. In contrast, the acrylic oligomers are soluble in water even when the atomic weight is about 7,000 Da. With these advantages, we used acrylic block oligomers as the exchanged ions to be intercalate in the layers of montmorillonite and study the effects of electron charge, charge density, hydrophobicity and block sequence on intercalation. Nanocomposites of epoxy and
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acrylic block oligomers intercalated montmorillonite were synthesized. The properties of the nanocomposites including Tg, water resistance and light transmittance are also reported. EXPERIMENTAL Mater ials Na+-montmorillonite with an exchange capacity of 145 mequiv/100g (CWC) was obtained from Nanocor Inc. Na+-montmorillonite with an exchange capacity of 96 mequiv/100g (CL-42) was donated by Pai Kong Ceramic Materials Co. LTD. All block copolymers were provided by Prof. Hui Chen of Department of Chemical and Material Engineering, National Central Unive
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