Jung-Yeol Kim

Intercalated polypyrrole/Na+-montmorillonite nanocomposite via an inverted emulsion pathway method

An inverted emulsion pathway polymerization method was introduced to synthesize conducting polypyrrole (PPy) into the layer of inorganic clay within a nanolevel, using dodecylbenzenesulfonic acid (DBSA) as both an emulsifier and a dopant. The synthesized PPy/Na þ montmorillonite (MMT) nanocomposite was confirmed to have a layered structure with a folded or penetrated PPy from X-ray diffraction, and it was further characterized via FT-IR spectroscopy. Four probes method was adopted to examine electrical DC conductivity. Electrorheological (ER) behavior of the nanocomposite dispersed in silicone oil was also investigated using a rotational rheometer equipped with a high voltage generator. q 2002 Published by Elsevier Science Ltd.

Synthesis and electrorheology of emulsion intercalated PANI-clay nanocomposite

Polymer-clay nanocomposite particles with polyaniline (PANI) and Na + -montmorillonite (MMT) were synthesized using an emulsion intercalation method and then adopted for electrorheological (ER) fluids by dispersing the synthesized nanocomposite particles in silicone oil. Insertion of the PANI into the layer of clay was examined by X-ray diffraction, which confirmed that the conducting PANI polymer chain was aligned with the layers of clay. Dodecyl benzenesulfonic acid (DBSA) adopted as both an emulsifier and a dopant was found to play an important role for PANI-clay nanocomposite, affecting conductivity of the nanocomposite particles and their ER properties. Furthermore, ER fluids composed of PANI-clay composite were observed to exhibit typical ER behavior with higher static yield stresses under an applied electric field.

Synthesis and electrorheological characteristics of polyaniline derivatives with different substituents

Various polyaniline (PANI) derivatives from different monomers such as o-methoxyaniline (MOA), o-ethoxyaniline (EOA), o-methylaniline (MA) and o-ethylaniline (EA) were chemically synthesized and then examined for their electrorheological (ER) application, by dispersing the synthesized PANI derivative particles into a non-conducting oil. Characteristics of PANI derivative particles were also studied by FT-IR, TGA and SEM analysis. Depending on the type of substituents in the polymer chain, electrical conductivity of the particles varied, possibly due to a steric hindrance of the substituent and different interchain interaction. From the steady shear ER measurement, the conductivity of particle was found to affect the ER property of the suspension.

Electron spin resonance signal of nanocomposite of conducting polypyrrole with inorganic clay

The sharp and broad electron spin resonance (ESR) signals from nanocomposites of conducting polypyrrole (PPy) with inorganic Na+-montmorillonite (MMT) clay were simultaneously observed. The decomposed linewidths (ΔHP-P) of the sharp and broad ESR peaks of the nanocomposites at room temperature were 0.44 G and 21 G, respectively. However, we observed one broad ΔHP-P(∼12 G) for the conducting PPy without the Na+–MMT clay. From the analyses of the observed ESR signals, we propose that the narrow ΔHP-P originates from the weak spin–orbit interaction of the intercalated nanolayers of the nanocomposites, while the broad ΔHP-P originates from the bulky conducting PPy on the outside of the clay particles. The thermogravimetric and differential scanning calorimeter results showed that intercalation in the nanocomposites induced the thermal stability. Coulomb interactions between the positively charged polymers of the intercalated nanolayers and the negatively charged surface of the clay play an important role in t...

Miscibility and rheological characteristics of biodegradable aliphatic polyester and linear low density polyethylene blends

Abstract Miscibility characteristics and rheological properties for blends of biodegradable aliphatic polyester (BDP) and linear low density polyethylene (LLDPE) were examined by both a dynamic mechanical thermal analyzer and rheometers. Eventhough this blend system was found to be immiscible from the glass transition values, the shear viscosity of the blend lies between both of the constituent components following the additivity rule with respect to the blending ratio and is fitted with Carreau model. Loss moduli are observed to be higher than storage moduli below a frequency of 10 s −1 , and storage modulus and loss modulus increase with the increase in LLDPE contents. In addition, modified Cole–Cole plots for both blend compositions at a fixed temperature and temperature at a fixed composition show that they are immiscible.

Physical characteristics of aniline/pyrrole copolymer

To prepare the copolymers composed of aniline (ANI) and pyrrole (PY), three different molar ratios of ANI and PY were adopted for a chemical oxidation polymerization. Characteristics of the synthesized copolymers were examined via an FT-IR, TGA and SEM analysis. The dc electrical conductivity σ dc (T) was also measured and then explained based on the polymeric structural changes using a variable range hopping (VRH) model.

Synthesis and characterization of polypyrrole/organoclay nanocomposite

*Soluble polypyrrole (PPY) was synthesized using sodium di(2-ethylhexyl) sulfosuccinate (NaDEHS) as a doping agent and then adopted to prepare an intercalated PPY/organo clay nanocomposite. Insertion of the PPY polymer chain into the layer of clay was confirmed by an X-ray diffraction. Its various physical characteristics were also examined via a TEM, SEM, TGA and NMR. Furthermore, its electrorheological (ER) property when the nanocomposite particles were dispersed in silicone oil was examined under an applied electric field.

Electrorheological fluids based on chitosan particles

Electrorheology (ER) is concerned with the effect of an applied electric field on the flow of fluids, including a sharp increase in shear viscosity and exhibition of a yield stress. Typical ER fluids are suspensions of polarizable particles dispersed in insulating oils [1]. Under an imposed electric field, the viscosity increases drastically, and the suspensions may even become solidlike due to induced particle dipoles. Furthermore, all the physical and mechanical property changes are virtually reversible as soon as the applied electric field is switched off [2]. The formulation of ER suspensions with optimal properties to control ER effects is determined by a number of factors such as particle concentration, particle size and size distribution, and electric and dielectric properties. Conventional fluids require active substrates, such as water [3], surfactant [4] and glycerin [5]. However, the main disadvantage of the water-activated systems is their limited temperature range [6]. Viscous and conductive heating of the fluid also causes waterloss, which results in a decrease in the fluid effectiveness. Furthermore, the presence of substantial amounts of water could lead to dielectric breakdown, corrosion, and high power consumption. Novel dry-base ER systems composed of inorganic and polymeric materials [7–9] possess several advantages and have been studied to meet the requirements of a broad working temperature range, reduced abrasion, and a relatively low current density. Examples include carboneous particle [10], zeolite [11, 12], and various polymer semi-conductors, such as acene quinone radical polymers [13, 14], poly(p-phenylene) [15], polyaniline [16–18], polyphenylenediamine [19], and copolyaniline [20, 21]. Recently, organic-inorganic hybrid particles, such as polyaniline-clay nanocomposite [22], polyaniline coated silica particle [23] and SANclay nanocomposite [24, 25], have also been adopted as materials for dry-base ER fluids. It is noted that these synthetic organic polymers possess either branched polar groups, such as amino, hydroxy, and amino-cyan, or repeated semi-conducting groups. The polar groups may affect the ER performance by acting as electron donors.

An Algorithm for Hoisting Time Calculation in Super-tall Building Construction

An installation of the construction lift has a few limitations by many constrains and these have influences on labor productivity, that can be changed by vertical-transportation management. In the super-tall building construction, a management of construction lift operation is one of the most important factor, but existing methodologies depend on skilled practitioners` experiences. And it is true that the expertise resulted by the experiences does not transfer to the next generation. This study is a part of lifting-management simulation development which aims at the optimal construction lift management. A proposed algorithm is focus on lifting time calculation considering an acceleration capability. This research evaluates the result accuracy using comparative analysis on simulation result and field measuring time.

EPR Signal of Nanolayer in Conducting Polypyrrole (PPy) Nanocomposites

We observed the very sharp EPR signals of the nanolayer of the intercalated PPy-DBSA in PPy-DBSA/Na + -MMT clay nanocomposite synthesized by inverse emulsion polymerization method. The g-value of EPR signal of the PPy-DBSA and the nanocomposite sample was 2.00432 (±0.00005) and 2.00263 (±0.00003), respectively. The line-widths (ΔH p-p ) of the broad peak and the sharp peak of the nanocomposite sample were 21.4 G and 0.44 G respectively at room temperature. The small ΔH p-p of the nanolayer of the nanocomposite originates from the weak spin-orbit interaction. The spin-spin relaxation time of the sharp EPR signal was ∼1.3×10 -7 sec, which is longer than that (∼5.5×10 -9 sec) of PPy-DBSA sample without clay. The density of states of the system was ∼0.085 states/ (eV ring) for the nanocomposite and ∼0.11 states /(eV ring) for the PPy-DBSA.