Geumcheon gu, South Korea
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Kim K.R.,PBR Chemical Inc. | Park E.-S.,Youngchang Silicone Co.
Plastics, Rubber and Composites | Year: 2016

Electro-conductive poly(vinyl alcohol)/multi-walled carbon nanotube (PVOH/MWNT) and poly (ethylene-co-vinyl alcohol) (EVOH)/MWNT nanocomposites were prepared by precipitation saponification method. The MWNT was functionalised by electron beam irradiation in air at 1200 kGy doses. The electrical resistivity, thermal and mechanical properties, and positive temperature coefficient (PTC) behaviour of these nanocomposites were investigated. The melting and crystallisation peak temperatures of both nanocomposite systems were shifted at a higher temperature with the increase in saponification time. Their crystallinity and mechanical strength also increased with saponification time, indicating an increase in intermolecular hydrogen bond between vinyl alcohol groups. With the saponification time, PTC peak temperature of EVA28/MWNT and EVA40/MWNT nanocomposites was shifted at a higher temperature and followed by a negative temperature coefficient (NTC) of resistivity. However, the saponified PVAc/MWNT nanocomposites showed only NTC behaviour over a temperature range of 30-140°C. © 2016 Institute of Materials, Minerals and Mining.

Jeon H.J.,Sangmyung University | Kim M.-N.,Sangmyung University | Park E.-S.,Youngchang Silicone Co.
Plastics, Rubber and Composites | Year: 2016

A series of biodegradable polyurethane (BIOU) elastomers were obtained by chain extension of polyurethane (PU) prepolymer with the addition of castor oil (CAO), epoxidized CAO (ECAO) or methoxylated CAO (MCAO). The BIOU elastomers obtained were characterised by Fourier transform infrared, scanning electron microscopy, differential scanning calorimetry and tensile tester. The melting peak of BIOU became undetectable with an increase in the content of the chain extender regardless of its type. Some BIOU films, including BIOU-CAO16wt%, BIOU-ECAO16wt% and BIOU-MAO16wt%, showed elastomeric properties with higher tensile strength than pure PU. However the elongation at break and hardness of samples decreased with CAO, ECAO and MCAO content. The biodegradation was also measured by the modified Sturm test method of the BIOU films in a cultured medium with Pseudomonas aeruginosa E7 and Lysobacter soli LW1-1 strains at 37°C. As the increasing three types of chain-extenders the degree and rate of biodegradation of BIOU increased as compared with pure PU. But even then the biodegradability of BIOU by both the strains did not exceed 26% during the modified Sturm test for 31 days. © 2015 Institute of Materials, Minerals and Mining.

Park E.-S.,Youngchang Silicone Co.
Iranian Polymer Journal (English Edition) | Year: 2011

The effects of electron beam (EB) irradiation on dielectric breakdown voltage (BDV) and insulation resistance ρl changes of poly(ethylene-co- tetrafluoroethylene) (ETFE) insulated electric wire were investigated. Electric wire was prepared by extruding pristine ETFE. The samples were irradiated in air at room temperature by a universal EB accelerator by doses ranging from 1 to 20 Mrad. The thermal behaviour of extruded samples has been also investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). When the ETFE insulated wire was exposed to EB irradiation, BDV and ρl were decreased gradually with irradiation dose. As the irradiation dose increased, the char formation and size of breakdown point were decreased significantly (above 10 Mrad). In TGA study, the thermal stability of EB-irradiated ETFE samples decreased significantly with radiation dose. For ETFE-20 the TGA traces showed a shift of the weight loss towards lower temperature with stabilization of 50anddeg;C lower than pristine ETFE. DSC Melting temperature (Tm) and crystallization temperature (Tc) of EB-irradiated ETFE tended to decrease as the irradiation dose increased. The crystallinity (andchi;) was slightly increased up to 5 Mrad irradiation dose and decreased significantly with irradiation dose above 5 Mrad. An increase in andchi; values occurred due to chain scission in the amorphous region, which led to crystallite perfection. The chain scission process created shorter polymer chain links which became easier to fit into a localized crystalline domain. At higher EB irradiation dose, the crystalline structure tended to be destroyed which led to decreases in Tm and Tc. After EB irradiation, the tensile properties and scrape abrasion resistance of ETFE were also decreased with respect to pristine ETFE.

Seob Jong Y.,Polyone Technology Co. | Han S.-H.,Korea Polytechnic University | Park E.-S.,Youngchang Silicone Co.
Polymer Composites | Year: 2011

Various output heating elements were extruded with carbon black (CB)-filled high-density polyethylene (HDPE) composites. After thermal aging near melting point of HDPE, the effects of thermal aging on the morphology, resistivity, and thermal properties of the extruded and electron beam (EB)-irradiated heating elements were examined using scanning electron microscopy (SEM) megohmmeter and differential scanning calorimetry, respectively. The heating element was insulated with a polytetrafluoroethylene tape wrap. The SEM image of HDPE is covered with microvoids that leave a dimple-like structure on the surface. As the percolation threshold is achieved, CB aggregates are usually located in oval cavities larger than the particles themselves. During the resistivity- temperature cycling test, significant change in resistivity was observed for extruded and EB-irradiated heaters. In case of thermal-aged samples at 140°C for 120 h, both heaters showed good stability without pronounced changes in resistivity after resistivity-temperature cycling test. After thermal aged at 140°C for 120 h, the Heater02-EB composite recovered the oval cavity structure, whereas for Heater02, the amorphous region became narrower and formed a more electroconductive pathway. © 2011 Society of Plastics Engineers.

Lee E.-J.,Korea Engineering Plastics Co. | Park E.-S.,Youngchang Silicone Co.
Polymer Composites | Year: 2015

Poly(ethylene-co-vinyl alcohol)/carbon black (EVOH/CB) composites were prepared by a solvent-casting saponification (-D) and precipitation saponification (-P) methods with a poly(ethylene-co-vinyl acetate)/CB (EVA/CB) toluene suspension. The effects of the CB content and saponification time on the morphology, electrical resistivity, thermal, and mechanical properties of EVA/CB composites were examined. The volume resistivity (ρv) of the EVA/CB-D and EVA/CB-P samples decreased significantly with increasing CB content and the percolation threshold of such composites was determined about 10 wt%. At 10 wt% of CB content, the ρv of EVA/CB-D composite decreased significantly with the saponification time, whereas ρv of EVA/CB-P composites did not change. As the saponification time increased, EVA/CB25wt% composites form cavity structure which CB is usually located in oval cavities larger than the particles themselves. This oval cavity structure almost resembles extruded high-density polyethylene (HDPE)/CB composites. The morphology and PTC behavior of prepared composites were compared with those of HDPE/CB and the mechanism of PTC and NTC effects was discussed. © 2015 Society of Plastics Engineers.

Lee E.-J.,Inha University | Yoon J.-S.,Inha University | Park E.-S.,Youngchang Silicone Co.
Journal of Applied Polymer Science | Year: 2012

Multiwalled carbon nanotubes (MWNTs) were functionalized by electron-beam (EB) irradiation in air at room temperature. As the EB dose was increased to 1000 kGy, Fourier transform infrared analysis detected the formation of carbonyl groups in the irradiated MWNTs. Poly(ethylene-co-vinyl alcohol)/MWNT nanocomposite particles were prepared by the incorporation of EB-irradiated MWNTs in a poly(ethylene-co-vinyl acetate) (EVA)/toluene solution and saponification in an ethanol/KOH solution. Scanning electron microscopy observation showed that the nanocomposite particles had a highly porous, spongelike structure of connected matrix polymers and MWNTs. At low EVA/MWNT concentrations, the particles were less porous, and the precipitated polymer phase had a granular structure. At high concentrations, the porosity increased, and the precipitated polymer phase became spongelike. The thermal and mechanical properties and the electrical resistivity change of the prepared nanocomposites were investigated. © 2012 Wiley Periodicals, Inc.

Lee S.S.,Si Chemical Co. | Lee S.S.,Korea Polytechnic University | Kim K.R.,Si Chemical Co. | Han S.-H.,Korea Polytechnic University | And 3 more authors.
Journal of Reinforced Plastics and Composites | Year: 2011

The nanocomposite powders of poly(ethylene-co-vinyl alcohol)/Na +-montmorillonite (EVOH/MMT) and EVOH/Loess were prepared by a solution-precipitation and saponification method. EVA/toluene/nanoclay suspensions were precipitated and saponified in ethanol/KOH solution in a heterogeneous manner. Tensile properties, morphology, and thermal behavior of the prepared nanocomposites have been evaluated using UTM, SEM, and DSC, respectively. The tensile strength and elongation at break of EVA/MMT-50% and EVA/Loess-50% nanocomposites were significantly increased up to 1 h saponification time and thereafter gradually decreased. At 1 h saponification time, the tensile strength of EVA/ Loess-50% nanocomposite was increased by 5.4-fold to 14.7 MPa, whereas EVA/MMT-50% increased the tensile strength by 2.2-fold to 10.4 MPa compared to the un-saponified one. With the increase in saponification time, melting and crystallization peak temperature of both nanocomposites was shifted at a higher temperature. The antibacterial activity of saponified EVA/MMT-50% and EVA/Loess-50% powders was also determined by shake flask test against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Among the nanocomposites used in this study, EVA/MMT-50%-6 h exhibited strong antibacterial activity against the two kinds of bacteria. © The Author(s) 2011.

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