• Bulletin of the Korean Chemical Society
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• 제27권11호
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• pp.1819-1824
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• 2006

The general objective of the present study was to investigate the potential application of the UV spectroscopic method for determination of the polymeric additives present in papermaking fibrous stock solutions. The study also intended to establish the surface-chemical retention model associated with the adsorption kinetics of additives on fiber surfaces. Polyamide epichlorohydrin (PAE) wet strength resin and imidazolinium quaternary (IZQ) softening agents were selected to evaluate the analytical method. Concentrations of PAE and IZQ in solution were proportional to the UV absorption at 314 and 400 nm, respectively. The time-dependent behavior of polymeric additives obeyed a mono-molecular layer adsorption as characterized in Langmuir-type expression. The kinetic modeling for polymeric adsorption on fiber surfaces was based on a concept that polymeric adsorption on fiber surfaces has two distinguishable stages including initial dynamic adsorption phase and the final near-equilibrium state. The simulation model predicted not only the real-time additive adsorption behavior for polymeric additives at high accuracy once the kinetic parameters were determined, but showed a good agreement with the experimental data. The spectroscopic method examined on the PAE and IZQ adsorption study could potentially be considered as an effective tool for the wet-end retention control as applied to the paper industry.

• 공업화학
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• 제16권1호
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• pp.117-122
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• 2005

가시광선 중합형의 치아수복용 고분자 복합체(polymeric dental restorative composites, PDRC)에 있어서 여러 종류의 3급 아민계 광증감제가 PDRC의 치과적 물성에 미치는 영향을 기계적 물성과 심미적 특성을 분석한 후 고찰하였다. PDRC 제조에 사용한 barium silicate 필러는 아크릴계 resin matrix와의 혼화성 증가를 위해 표면을 소수성으로 처리하여 사용하였다. 광중합에 필요한 광개시제로는 resin matrix를 기준으로 camphorquinone을 0.5 wt%로 하여 사용하였다. 그 결과, 제조된 PDRC의 기계적 물성과 심미적 특성은 사용한 광증감제의 함량보다는 화학적 구조에의 의존성이 더 큼을 알 수 있었다.

• Steel and Composite Structures
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• 제21권4호
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• pp.849-862
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• 2016

This paper investigates the static buckling behaviours of Functionally Gradient Polymeric Material (FGPM) shells in the form of hemispherical segment. A new FGPM model based on experimental was considered to investigate the buckling problem of thin-walled spherical shells loaded by the external pressure. The spherical shells were formed by FGPM which was produced adding the two types of graphite powders into epoxy resin. The graphite powders were added to the epoxy resin as volume of 3, 6, 9, and 12%. Halpin-Tsai and Paul models were used to determine the elastic moduli of the parts of FGPM. The detailed static buckling analyses were performed by using finite element method. The influences of the types and volume of graphite powders on the buckling behaviour of the FGPM structures were investigated. The buckling loads of hemispherical FGPM shells based on Halpin-Tsai and Paul models were compared with those determined from the analytical solution of non-graphite condition existing for homogeneous material model. The comparisons between these material models showed that Paul model was overestimated. Besides, the critical buckling loads were predicted. The higher critical buckling loads were estimated for the PV60/65 graphite powder due to the compatible of the PV60/65 graphite powder with resin.

• Carbon letters
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• 제1권1호
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• pp.1-5
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• 2000

The effect of surface free energy on the positive temperature coefficient (PTC) of carbon black/thermoplastic resin composites was investigated. The thermoplastic resins such as EVA, LDPE, LLDPE and HDPE were used with the addition of 30 wt.% of the carbon black. The surface free energy of the composites was studied in the context of two-liquid contact angle measurements, i.e., deionized water and diiodomethane. It was observed that the resistivity on PTC composites Was greatly increased near the crystalline melting temperature, due to the thermal expansion of polymeric matrix. From the experimental results, it was proposed that the decrease of surface free energy induced by interactions between carbon black surfaces and polymer chains is an important factor to the fabrication of a PTC composite made of carbon black and polymeric matrix.

• 공업화학
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• 제16권5호
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• pp.672-676
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• 2005

치아수복용 고분자 복합체(polymeric dental restorative composite, PDRC)의 전치부와 구치부에의 응용 가능성을 높이고자 PDRC를 구성하는 실리카 충진재를 다양한 온도에서 열처리시켜 siloxane 기로 연결된 구조의 개질된 실리카를 제조하고 이를 PDRC 제조에 사용하였다. 제조된 PDRC의 중합 특성을 중합전환률, 중합깊이, 그리고 체적 중합수축률 등을 분석하여 고찰하였다. 실험 결과, 사용된 실리카의 열처리 온도가 높아짐에 따라 제조된 PDRC의 중합깊이는 감소하였고 체적 중합수축률과 중합전환률 값은 실리카 입자의 평균크기 감소에 따른 PDRC 내 resin matrix의 상대적 양의 증가로 인해 일정하게 증가함을 알 수 있었다.

• Steel and Composite Structures
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• 제32권6호
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• pp.753-767
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• 2019

Vibration control in mechanical equipments is an important problem where unwanted vibrations are vanish or at least diminished. In this paper, free vibration active control of the porous sandwich piezoelectric polymeric nanocomposite microbeam with microsensor and microactuater layers are investigated. The aim of this research is to reduce amplitude of vibration in micro beam based on linear quadratic regulator (LQR). Modified couple stress theory (MCST) according to sinusoidal shear deformation theory is presented. The porous sandwich microbeam is rested on elastic foundation. The core and face sheet are made of porous and three-phase carbon nanotubes/resin/fiber nanocomposite materials. The equations of motion are extracted by Hamilton's principle and then Navier's type solution are employed for solving them. The governing equations of motion are written in space state form and linear quadratic regulator (LQR) is used for active control approach. The various parameters are conducted to investigate on the frequency response function (FRF) of the sandwich microbeam for vibration active control. The results indicate that the higher length scale to the thickness, the face sheet thickness to total thickness and the considering microsensor and microactutor significantly affect LQR and uncontrolled FRF. Also, the porosity coefficient increasing, Skempton coefficient and Winkler spring constant shift the frequency response to higher frequencies. The obtained results can be useful for micro-electro-mechanical (MEMS) and nano-electro-mechanical (NEMS) systems.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.793-796
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• 2003

This study dealt with the manufacturing process of self-healing microcapsules for damage repair in polymeric composites. The microcapsule was consisted with a DCPD (dicyclopentadiene) as the healing agent and a urea-formaldehyde resin as the wall section. The size distribution of microcapsules were measured by a particle size analyzer using a laser diffraction technique. Thermal stability of microcapsules was investigated by using a TGA under continuous and isothermal heating conditions. According to the results, these microcapsules were verified to be to thermally stable and have a great potential to be applicable for damage repair in polymeric composites.

• 한국분말재료학회지
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• 제17권1호
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• pp.59-64
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• 2010

8 mol% Y-doped $SrTiO_3$ powder was synthesized by Pechini method from titanium isopropoxide, strontium nitrate, yttrium nitrate, citric acid and ethylene glycol. A $Y_2Ti_2O_7$ pyrochlore phase-free perovskite powder was obtained by calcining a polymeric resin, which was prepared from a precursor solution, at $500^{\circ}C$ in an air atmosphere. Low temperature calcination could lead to a fine-grained microstructure. In the case of a solid-state reaction, an extended heat-treatment at high temperature in a reduced atmosphere needed to obtain a single phase perovskite $SrTiO_3$.

• Korean Chemical Engineering Research
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• 제48권5호
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• pp.568-573
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• 2010

본 연구에서는 polyester 섬유표면에 활성기를 부여하기 위한 전처리제로 isocyanate를 이용하여 농도에 따른 접착력을 평가하였다. 이 후 HNBR compound와 polyester fabric의 접착 시 접착력이 우수한 RFL 용액용 latex 선정 및 F/R mole ratio, F/R resin/latex 무게 비에 따른 실험을 진행하였다. 그 결과 전처리제의 농도가 7 wt%인 경우 가장 높은 접착력을 나타내었으며, RFL 용액용 latex로는 HNBR 컴파운드와 상용성이 높은 NBR latex가 우수한 결과를 나타내었고 F/R mole ratio, FR resin/latex 무게비가 각각 1/1, 20%일 때 가장 높은 접착력을 나타내었다. 또한, peel test와 FTIR 분석을 이용해 RF resin의 열처리 온도에 따른 접착강도와 spectra의 peak 변화를 평가해 본 결과 최적의 열처리 온도는 $200^{\circ}C$이었다.

• 도시과학
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• 제11권2호
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• pp.25-30
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• 2022

Resin Transfer Molding FRP (RTM FRP) is a fiber reinforced polymeric plastic which is manufactured by applying pressure to fibers, injecting resin into a mold, and then impregnating it. RTM FRP is a new construction material suitable for producing non-continuum structural elements such as sole plate because it has excellent strength and can produce many members in a short time. In this study, experiments were conducted to estimate the capacity of the bolted connection of RTM FRP. First, a tensile test was conducted to confirm the mechanical properties such as the tensile strength of the RTM FRP to be used for the bolted connection experiments. In addition, experiments were conducted on the bolted connection with the thickness of the RTM FRP and the edge distance of the bolt as variables. In the first experiment, F4.8 bolts were used, and shear failure of the bolt occurred before the RTM FRPs were failed. The F4.8 bolt is a general structural bolts used for the sole plate of a bridge bearing, and it was confirmed that the RTM FRP has a higher bold bearing strength than the shear strength of a F4.8 bolt. In the second experiment, G12.9 bolts were used, and shear failure of the bolt and bearing failure of the RTM FRP occurred simultaneously. In addition, as the thickness of the RTM FRP and the edge length of the bolt increased, the strength of the joint increased. When analogized with the bearing fracture equation of steel plate, the bolted connection of RTM FRP showed a bearing strength coefficient of 0.420 to 0.549 compared to the tensile strength, and it is considered that further research is needed.