• Composites Research
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• v.37 no.2
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• pp.68-75
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• 2024

Polypropylene (PP), a thermoplastic resin with excellent mechanical, thermal, chemical, and water resistance properties, has been attracting attention due to its economic efficiency and recyclability. However, repeated processing of thermoplastic resins can lead to property degradation, and the point at which quality degradation occurs varies depending on the processing conditions. In this study, we evaluated the performance changes of composite materials with repeated processing by blending PP resin with various additives and conducting extrusion and injection processes repeatedly. In addition, we evaluated the mechanical properties of composite materials to evaluate the effect of MFI value change during repeated processing on fiber impregnation in composite material processing.

• Journal of Food Hygiene and Safety
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• v.24 no.4
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• pp.352-356
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• 2009

The purpose of this study was to introduce the toxicological study review to evaluate the safety of PDMS on the 69th JECFA meeting. Polydimethylsiloxane is a polymer and its ADI was established at 23rd JECFA meeting in 1979. The ADI was maintained although the specification was expanded at its 26th, 29 th, 37 th meetings. Recently, it was reported that PDMS with low molecular weight and viscosity has high absorption rate and different toxicity, so it was submitted at 69th meeting. Toxicological studies of PDMS were submitted from the sponsor and additional information is collected from a document searching. The toxicological studies were reviewed in accordance with the 'Guidelines for the preparation of toxicological working papers for the Joint FAO/WHO Expert Committee on Food Additives'. In the available acute, sub-chronic and chronic toxicity studies on PDMS, dose-related increases in incidence and severity of ocular lesions(corneal crystal, inflammation of the corneal epithelium etc.) were consistently observed after oral dosing. It seems to be a local irritant effect, but the mechanism by which the ocular lesions arose is unclear, although the lack of absorption of PDMS indicates that it is unlikely to be a direct systemic effect. Consequently, the relevance of the ocular lesions for food use of PDMS could not be determined. The ADI of PDMS was re-established from 0-1.5 mg/kg bw/day to 0-0.8 mg/kg bw/day by applying additional safety factor 2 based on its ocular toxicity. The result of 0-0.8 mg/kg bw/day is a temporary ADI until further data are provided to 2010.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.80-81
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• 2012

Recently, one of the critical issues in the etching processes of the nanoscale devices is to achieve ultra-high aspect ratio contact (UHARC) profile without anomalous behaviors such as sidewall bowing, and twisting profile. To achieve this goal, the fluorocarbon plasmas with major advantage of the sidewall passivation have been used commonly with numerous additives to obtain the ideal etch profiles. However, they still suffer from formidable challenges such as tight limits of sidewall bowing and controlling the randomly distorted features in nanoscale etching profile. Furthermore, the absence of the available plasma simulation tools has made it difficult to develop revolutionary technologies to overcome these process limitations, including novel plasma chemistries, and plasma sources. As an effort to address these issues, we performed a fluorocarbon surface kinetic modeling based on the experimental plasma diagnostic data for silicon dioxide etching process under inductively coupled C4F6/Ar/O2 plasmas. For this work, the SiO2 etch rates were investigated with bulk plasma diagnostics tools such as Langmuir probe, cutoff probe and Quadruple Mass Spectrometer (QMS). The surface chemistries of the etched samples were measured by X-ray Photoelectron Spectrometer. To measure plasma parameters, the self-cleaned RF Langmuir probe was used for polymer deposition environment on the probe tip and double-checked by the cutoff probe which was known to be a precise plasma diagnostic tool for the electron density measurement. In addition, neutral and ion fluxes from bulk plasma were monitored with appearance methods using QMS signal. Based on these experimental data, we proposed a phenomenological, and realistic two-layer surface reaction model of SiO2 etch process under the overlying polymer passivation layer, considering material balance of deposition and etching through steady-state fluorocarbon layer. The predicted surface reaction modeling results showed good agreement with the experimental data. With the above studies of plasma surface reaction, we have developed a 3D topography simulator using the multi-layer level set algorithm and new memory saving technique, which is suitable in 3D UHARC etch simulation. Ballistic transports of neutral and ion species inside feature profile was considered by deterministic and Monte Carlo methods, respectively. In case of ultra-high aspect ratio contact hole etching, it is already well-known that the huge computational burden is required for realistic consideration of these ballistic transports. To address this issue, the related computational codes were efficiently parallelized for GPU (Graphic Processing Unit) computing, so that the total computation time could be improved more than few hundred times compared to the serial version. Finally, the 3D topography simulator was integrated with ballistic transport module and etch reaction model. Realistic etch-profile simulations with consideration of the sidewall polymer passivation layer were demonstrated.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.8 no.2
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• pp.49-59
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• 2002

The main function of plastic materials in food packaging is to preserve a food for safe transportation and storage. The interactions between food and plastic materials in food packaging have become increasingly important for food quality and safety because monomer, low molecular weight components, or additives of plastic packaging materials can migrate into a food. The use of antioxidants in plastic materials can help protect the degradation of film itself and retard the oxidation of a packaged food containing lipid, through the migration of antioxidant from the packaging to a product via an evaporation / sorption mechanism. Nowadays, antioxidant (BHT) impregnated plastic materials are used for commercial food packaging application with the intention of achieving an extended shelf life of food in USA. Alpha tocopherol, as one of the most important free radical scavengers, has been well known in biological systems. Moreover, the potential use of alpha tocopherol as an additive for polymers used in the packaging industry may offer the most positive perception from both consumers and manufacturers. Alpha tocopherol has been used as an antioxidant for polyolefin resins fabricated to both bottles and film and has applications in the food packaging industry as a replacement for BHT. Today, alpha tocopherol offers an attractive choice for use as an antioxidant in polymers. This paper provides an overview of antioxidant effectiveness and applications for its use by the food packaging industry based on the evaporation-sorption mechanism of a packaging model product, where quality is associated with lipid oxidation. Important analytical techniques for predicting antioxidant interaction between the package system and product are discussed.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2005.09a
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• pp.201-212
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• 2005

[ $Epoxy/BaTiO_3$ ] composite embedded capacitor films (ECFs) were newly designed fur high dielectric constant and low tolerance (less than ${\pm}15\%$) embedded capacitor fabrication for organic substrates. In terms of material formulation, ECFs are composed of specially formulated epoxy resin and latent curing agent, and in terms of coating process, a comma roll coating method is used for uniform film thickness in large area. Dielectric constant of $BaTiO_3\;&\;SrTiO_3$ composite ECF is measured with MIM capacitor at 100 kHz using LCR meter. Dielectric constant of $BaTiO_3$ ECF is bigger than that of $SrTiO_3$ ECF, and it is due to difference of permittivity of $BaTiO_3\;and\;SrTiO_3$ particles. Dielectric constant of $BaTiO_3\;&\;SrTiO_3$ ECF in high frequency range $(0.5\~10GHz)$ is measured using cavity resonance method. In order to estimate dielectric constant, the reflection coefficient is measured with a network analyzer. Dielectric constant is calculated by observing the frequencies of the resonant cavity modes. About both powders, calculated dielectric constants in this frequency range are about 3/4 of the dielectric constants at 1 MHz. This difference is due to the decrease of the dielectric constant of epoxy matrix. For $BaTiO_3$ ECF, there is the dielectric relaxation at $5\~9GHz$. It is due to changing of polarization mode of $BaTiO_3$ powder. In the case of $SrTiO_3$ ECF, there is no relaxation up to 10GHz. Alternative material for embedded capacitor fabrication is $epoxy/BaTiO_3$ composite embedded capacitor paste (ECP). It uses similar materials formulation like ECF and a screen printing method for film coating. The screen printing method has the advantage of forming capacitor partially in desired part. But the screen printing makes surface irregularity during mask peel-off, Surface flatness is significantly improved by adding some additives and by applying pressure during curing. As a result, dielectric layer with improved thickness uniformity is successfully demonstrated. Using $epoxy/BaTiO_3$ composite ECP, dielectric constant of 63 and specific capacitance of 5.1nF/cm2 were achieved.

• Journal of the Korean Society for Marine Environment & Energy
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• v.20 no.2
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• pp.107-116
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• 2017

When drilling operation is being performed, many physical and chemical changes are occurred near wellbore. To handle various changes of well condition and keep drilling process safe, additives of bulk, such as bentonite for increasing density of drilling mud, barite for increasing viscosity of drilling mud, polymer for chemical control, or surfactant, are added into drilling mud through a mud shear mixer. Because the achievement of the required material property through mud mixing system is essential to stabilize drilling system, it is of importance to analyze multi-phase flow during mud mixing process, which is directly related to increase mixing performance of the system and guarantee the safety of the whole drilling system. In this study, a series of liquid-solid flow simulation based on a computational fluid dynamics (CFD) are performed with comparing to solid concentration in experiment by Gilles et al. [2004] to understand the characteristics of liquid-solid mixing in a mud shear mixer. And then, the simulation-based design of shear mixer are carried out to improve mixing performance in a mud handling system.

• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.135-140
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• 1998

The constituents of deposits on paper machine and holes/spots in paper have been analyzed by a combination of analytical techniques, such as FTIR, Py-GC-MS, and EDS. FTIR spectroscopy was used prior to Py-GC-MS and EDS analysis, as a preliminary analysis. The analysis of organic components was carried out with a pyrolysis unit connected to a GC-MS, and inorganic components in ash were analyzed by SEM equipped with an EDS analyzer after pyrolysis at $590^{\circ}C$. The deposits on the dryer section were complex pitch, which was the mixture of the organic components of fatty acid ester and starch, and the inorganic components of talc, clay, and calcium carbonate. The complex pitch was estimated to come from the coated broke. We knew the deposits on the metering rod of sym-sizer were associated with the interaction of unstable alkyl keten dimer(AKD) and $CaCO_3$. The compositions of holes or spots varied considerably and were associated with chemical interaction within the system. The holes, spots, and blotches in the finished paper were PE and PP from pulp sources, complex pitch that were caused by the interaction of the different additives in the system, polymer such as flexible PVC that was used for the prop of palette, and hot melt as adhesives that came from the inadequate handling of broke. In addition, we identified that poly(caprolactam) which is used for forming fabrics or press felts, could be mixed with the raw materials by accident and results in streaks on coating.

• Korean Journal of Food Science and Technology
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• v.29 no.1
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• pp.138-144
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• 1997

A new biopolymer YU-122 from Metarrhizium anisopliae (Metschn.) Sorok consisting of glucose and galactose was tested for its physical properties and flow behavior characteristics. Xanthan gum showed slightly higher viscosity than biopolymer YU-122. Viscosity of biopolymer YU-122 at various pHs and temperatures was also tested. The viscosity of biopolymer YU-122 was very stable up to pH 11 and $60^{\circ}C$, indicating that it has a great possibility for the application such as food additives, emulsifier, and drug release agents. Flow behavior index (n) from Power Law equation is 0.173. Biopolymer YU-122 solution was a pseudoplastic non-Newtonian fluid, which indicated that it had one or more side chains. When biopolymer YU-122 was used as a emulsifier, it stabilized the emulsion up to 120 hours, which was much better than xanthan gum. The biopolymer YU-122 could form an excellent but less clear film compared with xanthan and pullulan.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.888-894
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• 2015

Inorganic composite particles have excellent physical and chemical characteristics and have been applied in various industries. Recently, many studies have examined the optical properties, such as light scattering, refraction, transmission characteristics, by coating organic-inorganic materials on a substrate, such as mica. Mica is widely applied as a pigment, plastics, painted products, and ceramics because of its high chemical stability, durability and non-toxicity. Magnesium oxide has a range of properties, such as high light transmittance, corrosion resistance and non-toxicity, and it is used as an optical material and polymer additives. To use the optical properties of mica and magnesium oxide, mica was coated with magnesium hydroxide by a dissolution and recrystallization process. In this study, the optimal conditions for the haze value of the particles were found by adjusting the amount of precursors and pH. Magnesium hydroxide layers were formed on the surfaces of mica and converted to MgO after calcination at $400^{\circ}C$ for 4 h. The results showed that the value of MgO-coated mica haze can be controlled easily by the amount of the magnesium hydroxide and pH. The optical properties of the inorganic composite powder were analyzed using a hazemeter and the highest haze value was 85.92 % at pH 9. The physicochemical properties of the synthesized composite was analyzed by SEM, XRD, EDS, and PSA.

• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.698-706
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• 2019

Over the last few decades, there have been a lot of efforts to develop soft actuators, which can be external stimuli-responsive and applied to the human body. In order to fabricate medical soft actuators with a dynamic precision control, the 3D crosslinked poly(acrylic acid) (PAAc)/poly(vinyl alcohol) (PVA)/poly(ethylene glycol) (PEG) hydrogels were synthesized in this study by using a radiation technique without noxious chemical additives or initiators. After irradiation, all hydrogels showed high gel fraction over 75% and the ATR-FTIR spectra indicated that PAAc/PVA/PEG hydrogels were successfully synthesized. In addition, the gel fraction, equilibrium water content, and compressive strength were measured to determine the change in physical properties of PAAc/PVA/PEG hydrogels according to the irradiation dose and content ratio of constituents. As the irradiation dose and amount of poly(ethylene glycol) diacrylate (PEGDA) increased, the PAAc/PVA/PEG hydrogels showed a high crosslinking density and mechanical strength. It was also confirmed that PAAc/PVA/PEG hydrogels responded to electrical stimulation even at a low voltage of 3 V. The bending behavior of hydrogels under an electric field can be controlled by changing the crosslinking density, ionic group content, applied voltage, and ionic strength of swelling solution.