• Composites Research
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• v.27 no.6
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• pp.236-241
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• 2014

This paper aims to evaluate material property variation of polymer concretes under ultra-violet exposure condition. The components and mixing ratio of the polymer composite specimens were determined by the previous research results. The equivalent UV exposure time was calculated with the consideration of the power of metal halide lamp and maximum 3 years were selected for the experiments. From the tests, it was found that the generated heat during UV exposure affected much the material properties of polymer concrete by means of post cure. As a result, the compressive strength increased and ductility factor decreased.

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.1
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• pp.119-124
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• 2001

Dimethyl terephthalate (DMT). 1.4-butanediol (1.4-BD) and poly (tetramethylene ether) glycol (PTMG) in the molecular weight of 2000 (g/mol) were used to synthesize poly(ether-b-ester) thermoplastic elastomers (TPEEs). The final copolymers were annealed to improve thermal stability at elevated temperatures and mechanical properties. This study showed that as the proportion of soft segment increases melting temperature and degree of crystallinity of TPEEs decrease constantly. In case of mechanical properties like flexural strength and flexural elastic modulus. $35-PTMG^{2000}$ indicates the highest values due to more efficient physical interlock.

• Polymer(Korea)
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• v.24 no.5
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• pp.599-609
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• 2000

In order to improve the mechanical properties of unsaturated polyester (UPE) resins, the UPE resins with different glycol molar ratios were prepared. The effects of molar ratios of the UPE resins on the curing behaviors and mechanical properties were investigated. The microgel reaction mechanism was employed to characterize the system. It was found that the final conversion increased with increasing NPG molar ratios, and the conversion at the peak of differential scanning calorimetry (DSC) thermogram appeared to decrease with increasing NPG molar ratios. The flexural strength, tensile modulus, water resistance, and infiltration increased with increasing NPG content, but the tensile strength, tensile elongation, and flexural modulus decreased. Among the UPE resins prepared from the glycols with the molar ratios (PG/NPG) of 0.5/0.5, 0.25/0.75, those of laminated composites plates showed better mechanical properties.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.56-56
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• 2004

섬유강화 복합재료는 응용범위가 산업계 전반으로 빠르게 확대되고 있다. 개발 초기에는 하중을 감당하지 않는 이차 구조물에 주로 사용되어 왔으나, 점차 산업 전반의 I차 구조물(Primary Structure)에 쓰이는 등, 그 사용범위가 넓어지고 있으며, 취약한 두께방향 물성 향상의 필요성을 충족시키기 위해 다축경편(MWK) 복합재료에 대한 연구가 진행되고 있다. 본 논문에서는 다축경편(MWK) 복합재료의 기계적 체결부에 관한 응력해석을 연구하였다.(중략)

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.341-349
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• 1996

To improve the dyeability of polyurethane (PU) resin, low molecular weight diols containing dye site in the molecular structure was added as a chain-extender. PU resin were synthesized with the variations in the chain extender, polyol type, and hard segment/soft segment (HS/SS) ratio. When HS/SS ratio is 1.4 and dimethylolpropionic acid(DMPA) or N-butyldiethanolamine (BDEA) was used as a chain extender, because of heterogeneity of reaction mechanical properties were diminished. But when N-methyldiethanolamine (MDEA) was used as a DCE, and HS/SS ratio lowed to 1.3, mechanical properties and dyeability improved. In particular, when linear type 1,4-BD was formulated with MDEA, hydrolysis resistance and mechanical properties of PTMG type PU was improved. And initial elasticity, tensile strength and elongation could be controlled by the variation of HS/SS ratio, DCE mixing ratio of 1,6-HD or NPG.

• Polymer(Korea)
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• v.27 no.3
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• pp.183-188
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• 2003

The dielectric constants of fluorine-containing epoxy resins, 2-diglycidylether of benzotrifluoride(FER)/4,4'-diamino-diphenyl methane (DDM) and diglycidylether of bisphenol-A (DGEBA)/DDM systems were evaluated by dielectric spectrometer. Glass transition temperature and thermal stability factors, including initial decomposed temperature, temperatures of maximum rate of degradation, and decomposition activation energy of the cured specimens were investigated by dynamic mechanical analysis and thermogravimetric analysis. For the mechanical properties of the casting specimens, the fracture toughness, flexural, and impact tests were performed, and their fractured surfaces were examined by scanning electron microscope. The dielectric constant of FER/DDM system was lower than that of commercial DGEBA/DDM system, and the mechanical properties of the cured specimens showed higher values than those of DGEBA/DDM system. This was probably due to the introduction of trifluoromethyl (CF$_3$) group into the side chain of the epoxy resins, resulting in improving the electric and mechanical properties of the epoxy cure system studied.

• Applied Chemistry for Engineering
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• v.24 no.1
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• pp.104-111
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• 2013

Poymer blends of two degradable aliphatic polyesters, relatively expensive material polylactic acid (PLA) and relatively inexpensive material poly(butylene adipate-co-terephthalate) (PBAT), were used in this study. Three different kinds of modifiers were used with various amounts. Diisocyanate type methylenediphenyl 4,4'-diisocyanate (MDI) and hexamethylene diisocyanate (HDI) were used as modifiers and epoxy type coupling agents also used. The melt flow index (MFI) and dynamic viscoelasticity of various compositions of PLA/PBAT blends were studied. The mechanical property and morphology with respect to the fracture surface of PLA/PBAT blends were also investigated using tensile test and field emission scanning electronic microscopy, respectively. These tests were also used to verify the compatibility of PLA/PBAT and the effect of mechanical properties due to the use of modifiers. Tensile properties of PLA/PBAT blends modified with HDI were improved remarkably.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.4
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• pp.113-117
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• 2020

In this paper, We investigated the effect of heat treatment process using photo-thermal effect in order to improve mechanical properties of nanostructure on polymer films made by nanoimprint process with hybrid resin. Nanostructures which have a low refractive characteristic were fabricated by UV nanoimprint and after that heat treatment was performed using IPL (intense pulsed light) under process condition of 550 V voltage, pulse width 5 ms, frequency 0.5 Hz. The transmittance and mechanical property of fabricated nanostructure films were evaluated to observe changes in the pattern transfer rate and mechanical properties of nanostructures. The transmittance of the nanostructure was measured at 97.6% at 550 nm wavelength. Nanoindentation was performed to identify improved anti-scatch properties. Result was compared by the heat source. In case of post treatment with IPL, hardness was 0.51 GPa and in the case of hotplate was 0.27 GPa, resulting the increase of hardness of 1.8 times. Elastic modulus of IPL treated sample was 5.9GPa and Hotplate treated one was 4GPa, showing the 1.4 time increase.

• Journal of Aerospace System Engineering
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• v.16 no.6
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• pp.8-17
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• 2022

This paper presents a novel geometric modeling technique to predict the mechanical properties of an aircraft wing's skin-stringer integrated panel. Due to mechanical and adhesive fastening, this panel is vulnerable to stress concentration and debonding, so we designed it to integrate the skin and stringer using three-dimensional woven composites. Geometric modeling was conducted by measuring the geometric parameters of the specimen and defining the pattern of the yarns as functions. We used a weighted average model with iso-strain and iso-stress assumptions to predict the mechanical properties of the panel parts. We then compared the results of a finite element analysis with a compression test to verify the accuracy of our model. Our proposed technique proved to be more efficient than the traditional experimental method for predicting the mechanical properties of skin-stringer integrated panels.

• Elastomers and Composites
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• v.37 no.4
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• pp.258-264
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• 2002

In this work, the influence of thermal treatment on surface properties of silicas and mechanical interfacial properties of silicas/polyurethane composites was investigated. The surface properties of thermally treated silicas were studied in the context of Fourier Transform-IR (FT-IR), solid-state 29Si NMR spectroscopy, and contact angle. And the mechanical interfacial properties of the silica/polyurethane composites were evaluated by composite tearing energy (GIIIC). As a result, it was found that the thermally treated silica surfaces became hydrophobic in nature, due to the condensation of surface hydroxyls and the formation of siloxane bonds, resulting in increasing the London dispersive component of surface free energy. From which, the increase of the London dispersive component of the silicas led to an improvement of the dispersion of silicas in a polyurethane matrix, finally resulting in improving the tearing energy (GIIIC) of the silicas/polyurethane composites.