• Applied Microscopy
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• v.38 no.3
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• pp.251-257
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• 2008

Human hair experience tensile forces during combing, bleaching and permanent dyeing processes. We have used rheometer to characterize bleached hair tensile response. Also, we investigated to morphological changes after tensile test of virgin hair and bleached hair using scanning electron microscopy. In tensile test, the tensile strength of virgin hair was $14.66g/cm^2$. They were measured as $12.95g/cm^2$, $12.61g/cm^2$ and $11.43g/cm^2$ for after the first, the second and the third trials of bleaching were done, respectively. Virgin hair had a higher tensile force than bleached hair. Tensile strength got lowered as more bleaching trials were done. In the observation of scanning electron microscopy, the fracture and lift-off of the cuticle outer layer were shown in virgin hair and bleached hair. The bleached hair were more lifted off at the outer cuticle layer than virgin hair. Consequently, chemical damage of bleaching agent caused weakening of the outer cuticle in the hair.

• Applied Microscopy
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• v.39 no.1
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• pp.49-56
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• 2009

In this study, we investigated tensile properties and ultrastructural changes of straight permed hair using the rheometer and the scanning electron microscopy. First, we compared the morphological characteristic between the virgin hair and the straight permed hair after testing tensile strength. Cuticle cells were heavily lifted off in straight permed hair than in the virgin hair. Cuticle cells were separated by the destruction of intercellular membrane complex and no destruction or damage were found in cytoplasm. In the comparative test for tensile characteristic between the virgin hair and the straight permed hair, tensile distance of the straight permed hair was decreased by 24.5% or 3.05 mm than the virgin hair. The tensile strength was decreased by 34.63% or $5.62\;g/cm^2$ and the maximum stress by 34.59% or 56.12 g. As a result, the tensile property dropped to the lowest level with the straight permed hair than with the bleached hair or the permanent dyed hair of previous studies.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.4
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• pp.83-87
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• 2022

Recently, as the thickness of the semiconductor package becomes thinner, warpage has become a major issue. Since the warpage is caused by differences in material properties between package components, it is essential to precisely evaluate the material properties of the EMC(Epoxy molding compound), one of the main components, to predict the warpage accurately. Especially, the cure shrinkage of the EMC is generated during the curing process, and among them, the effective cure shrinkage that occurs after the gelation point is a key factor in warpage. In this study, the gelation point of the EMC was defined from the dissipation factor measured using the dielectric sensor during the curing process similar with actual semiconductor package. In addition, DSC (Differential scanning calorimetry) test and rheometer test were conducted to analyze the dielectrometry measurement. As a result, the dielectrometry was verified to be an effective method for monitoring the curing status of the EMC. Simultaneously, the strain transition of the EMC during the curing process was measured using the FBG (Fiber Bragg grating) sensor. From these results, the effective cure shrinkage of the EMC during the curing process was measured.

• Elastomers and Composites
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• v.27 no.4
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• pp.247-254
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• 1992

The purpose of this dissertation is to study the vulcanization characteristics, compression set and other physical properties of NBR vulcanizates according to the various plasticizer and its content. Vulcanization characteristics were investigated by using cure that has obtained by means of rheometer and Mooney viscometer. The result of physical properties, vulcanization characteristics are as fellows. 1. The results of test for optimum cure time in vulcanization characteristics of NBR compounds indicated the rapidity of scorch time according to the increase of amounts of plasticizer. 2. In the test of compression set property, LCR was the best effect. 3. In the test of oil resistance, LCR was the best effect.

• Elastomers and Composites
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• v.16 no.1
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• pp.3-13
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• 1981

The purpose of this dissertation is to study the physical properties of cellular rubber products for industrial use. Vulcanization characteristics were investigated by usingcure curve that had obtained by means of Rheometer. The results of physical properties, vulcanization characteristics and foaming states are as follows. 1. The test results for vulcanization characteristics of NR compounds indicated that in the recipe R-1. When accelerator D is used, the optimum conditions of vulcanizate are obtained, while formula R-2 and R-3 have shown higher torgue at curing time, $1{\sim}2$ minutes. Cellular rubber product test in terms of compression set and compression deflection has also met the requirements of SAE. 2. For SBR compounds, S-1 formula was the best in terns of vulcanization characteristics, and for the blowing structure of cellular rubber products, formula S-3 in which accelerator M is added was fair. All other test results, such as compression set and compression deflection properties met SAE requirements. 3. NBR compound (N-1) including accelerator TT was the best in terms of vulcanization characteristic and also blowing structure. All other properties listed above met requirements, particulary for oil resistance test. 4. In the test of EPDM compounds, when mixed accelerator, M and TT, is used(formula E-1) the best results were obtained. Since EPDM is hydrocarbon elastomer, oil resistance test failed. All other properties met the requirement specified in SAE.

• Elastomers and Composites
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• v.50 no.1
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• pp.49-54
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• 2015

Dynamically vulcanized PMMA/ACM (80 wt%/20 wt%) blend using DCP as a curing agent was prepared using internal mixer. The morphology, mechanical properties, optical properties, melt viscosity and die swell were characterized by using FE-SEM, tensile test, Izod impact test, dynamic mechanical analysis, ARES and capillary rheometer, respectively. The blends show a phase-separated morphology in which ACM are dispersed in PMMA matrix. Dynamically vulcanized blend exhibits higher mechanical properties, higher melt viscosity, and die swell as compared to simple blend. And, the dynamically vulcanized blend showed total transmittance of more than 75% and haze of higher than 90%, which enable it to find potential applications to fabricate an optical diffuser by extrusion process.

• Elastomers and Composites
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• v.55 no.1
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• pp.40-45
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• 2020

In this study, the mechanical and flame-retardant properties of ethylene-propylene-diene-termonomer (EPDM) based rubber compounds and various other environmentally friendly inorganic flame retardants were investigated. Alumina trihydrate (ATH) and magnesium hydroxide (MDH) were used as inorganic flame retardants. The mechanical properties after thermal oxidation aging and the flame-retardant properties of the EPDM compounds were measured using a moving die rheometer, a universal testing machine, a compression set, and a UL 94 V flammability test. We focused on how the properties were affected by the type and amount of flame retardants. The results demonstrated that the optimal mechanical and flame-retardant V-0 grade properties were obtained at an ATH content of 200 phr.

• Journal of the Korean Society of Safety
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• v.33 no.6
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• pp.50-57
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• 2018

The purpose of this study is to evaluate the practical application of the self consolidating concrete for the steel concrete pannel (SCP) in module LNG storage tank proposed in the previous research. We evaluated the physical properties and filling performance of developed concrete for the SCP module. First, a slump flow test was conducted to evaluate the performance of the proposed guidelines for the filling test. As a result, all of the concrete used showed satisfactory performance. Based on the results of the previous study, it was found that the reliability of the required time measured by the $T_{500}$ test and the rheometer results measured before and after pumping was 0.94 which means the separation and blocking should not occur. The L-box test and the U-box test were conducted before and after pumping. All of the guidelines suggested showed satisfactory performance. SCP module for LNG storage tanks was fabricated on actual size scale to evaluate the practical application at the final site. As a result, it was confirmed that satisfactory filling performance was obtained in all the specimens.

• Journal of the Korean Graphic Arts Communication Society
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• v.23 no.2
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• pp.1-14
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• 2005

Generally, printing inks are composed of pigment, vehicle and additive. Among others, the vehicle transfers the pigment to substrate and then binds it on the surface. So, rheological properties of the vehicle are an important factor which has influence on printability. Thus, in this study, rheology of the vehicle was investigated by using rotational rheometer according to molecular weight of resin. Also, emlusion rheology of water in oil type and its microstructure were examined with increasing the shear rate. Consequently, the following results were obtained: (1) By viscometric flow test, zero shear viscosity and shear thinning index of vehicle increased with increasing the molecular weight of resin. (2) By relaxation and creep test, relaxation time and retardation time of vehicle increased with increasing the molecular weight of resin. (3) By frequency sweep test, crossover point of vehicle increased with increasing the molecular weight of resin. (4) G' and G" of emlusions increased with increasing the molecular weight by amplitude sweep test. (5) The shape of water drop in emlusions was changed to the capillary tube.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.3
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• pp.311-316
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• 2008

Calcium phosphate cement (CPC) has been used as bone substitute successfully due to good biocompatibility and osteoconductivity. One of the important mechanical characteristics of CPC is flowablility, which can be evaluated by measuring rheological parameters. However, there have been few studies that measured rheological properties of CPC. The purpose of this study was to evaluate the rheological properties of CPC paste mixed with 2 kinds of setting solutions, 2% hydroxyprophyl methylcellulose (HPMC) and 35% polyacrylic acid (PAA). The CPC used was dicalcium phosphate dihydrate (DCPD). Rheological properties of CPC paste were measured using rheometer. The statistical analysis was carried out with Mann-whitney test with Bonferronis collection. CPC with both setting solutions showed shear thinning behavior. CPC with 2% HPMC showed signigicantly higher complex viscosity than CPC with 35% PAA(p<0.05).