CNT/PMMA 복합체의 유변물성

초록

In this study, we prepared MWNT/poly(methyl methacrylate) (PMMA) nanocomposites with both a bulk type and a particulate type via a conventional in-situ bulk polymerization and a suspension polymerization, respectively, and then examined their rheological characteristics. Prior to use we purified the MWNT which was synthesized by a thermal chemical vapor deposition method, to eliminate impurities such as metallic catalysts. Purity of the pristine MWNT was 97 %, and it was treated in 3M HNO3 at 60 oC for 12 h, followed by a reflux process in 5 M HCl at 120 oC for 6 h with stirring1. At first, the acid-treated MWNT was dispersed in a liquid state of methyl methacrylate (MMA) monomer. An ultrasound was then applied to the MWNT dispersion using an ultrasonic generator. Polymerizations of MMA and MWNT/MMA dispersion were conducted using 2,2-azobisisobutyronitrile (AIBN) as an initiator in capped glass test tubes at 65 oC. After in situ bulk polymerization, the MWNT/PMMA composites were characterized by a Fourier transform infrared spectrometer. A scanning electron microscopy and a gel permeation chromatograph were adopted to characterize the molecular weight of the PMMAs in a tetrahydrofuran solution. We also used a rotational rheometer with a parallel-plate geometry to measure the shear viscosity in molten state2. On the other hand, MWNT and MMA were synthesized via a suspension polymerization using poly(vinyl alcohol) as a surfactant. The deionized water containing ammonium peroxydisulfate was added later through dropping, with continuous stirring and ultrasonication for 24 h at 20 oC. The MWNT/PMMA composites were separated three times by centrifugation. An ER fluid was prepared by suspending MWNT/PMMA particles in an insulating silicone oil, and its electrorheological property was examined under an applied DC electric field. The flow curves of MWNT/PMMA particles based ER fluid was measured by a rotational rheometer equipped with a high DC voltage generator3.