• Design & Manufacturing
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• 제17권1호
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• pp.1-5
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• 2023

In multi-material injection molding, since two or more materials with different process conditions are used, it is essential to maximize process efficiency by operating the cooling or heating system to a minimum. In this study, Liquid silicone rubber (LSR) that can be cured at a low temperature suitable for the multi-material injection molding was selected and the cure behavior according to the process conditions was analyzed through differential scanning calorimetry (DSC). Dynamic measurement results of DSC with different heating rate were obtained, and through this, the total heat of reaction when the LSR was completely cured was calculated. Isothermal measurement results of DSC were derived for 60 minutes at each temperature from 80 ℃ to 110 ℃ at 10 ℃ intervals, and the final degree of cure at each temperature was calculated based on the total heat of reaction identified from the Dynamic DSC measurement results. As the result, it was found that when the temperature is lowered, the curing start time and the time required for the curing reaction increase, but at a temperature of 90 ℃ or higher, LSR can secure a degree of cure of 80% or more. However, at 80 ℃., it was found that not only had a relatively low degree of curing of about 60%, but also significantly increased the curing start time. In addition, in the case of 110 ℃, the parameters were derived from experimental result using the Kamal kinetic model.

• 한국전기전자재료학회논문지
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• 제17권1호
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• pp.59-64
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• 2004

We have fabricated the polymer dispersed liquid crystal (PDLC) cell where a control of phase separation is very important. The factors to influence the phase separation are mixing ratio of LC and polymer, curing temperature and UV intensity. In this paper, we inspected the change of a phase separation as a function of curing temperature for the mixture of E7 and. NOA65 with different ratios. When the LC concentration is less than polymer such as LC:NOA65 = 40:60wt％, the PDLC cell is influenced strongly by the curing temperature. However, when the LC concentration is much less than polymer such as LC:NOA65 = 80:20wt％, it is influenced slightly by the curing temperature. The reason is because the mixture shows upper critical solution temperature behavior and therefore it is important to know the behavior of phase separation as a function of curing temperature of the mixture.

• 접착 및 계면
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• 제10권2호
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• pp.84-89
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• 2009

The objective of this research was to investigate the curing behavior and adhesion performance of urea-melamine-formaldehyde (UMF) resin for the four types of UMF-1, UMF-2, UMF-3, and UMF-4 which synthesized by the staged addition of melamine. Also, various network structures of these resin types were discussed based on their different curing behavior and adhesion performance. The curing behavior was evaluated by DMTA and thermal stability was checked by TGA. Adhesion performance was evaluated by dry and wet shear strengths and the pH value of each cured resin was checked to see its effect on the adhesion performance. The results indicated that the UMF-1 resin type by the addition of melamine initially with the urea and formaldehyde at the same F/(U+M) rate showed the lowest thermal stability, rigidity (${\Delta}E^{\prime}$), temperature of tan ${\delta}$ maximum ($T_{tan}\;_{\delta}$), and wet shear strength, and pH value of cured resin. In wet shear strength, however, the UMF-4 resin type appears to be slightly higher than UMF-1 resin type.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표회 논문집(I)
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• pp.185-190
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• 1998

Corrosion of steel reinforcement is the most significant factor of deterioration in reinforced concrete structures. Chloride ion is considered one of the most common culprits on the corrosion of steels in concrete. The main objective of this study is understanding behavior of chloride ion in hardened cement pastes at different stages of curing. Cement pastes with water-cement ratio of 0.5 are allowed to hydrate in sealed containers for 28, 70, 180 days. And than pore solution is expressed. It was found that the $Cl^-$ concentrations in pore solution is decreased with increasing curing time in all Nacl addition level, the $OH^-$ concentrations is increased to 70 days but decrease at 180 days in all Nacl addition level. The $Cl^-$/$OH^-$ in pore solution is increased with increasing curing time in all Nacl addition level, however $Cl^-$/$OH^-$ of maximum Nacl addition level(Nacl 0.54% by weight of cement) is under the onset of depassivation level 0.3.

• Korea-Australia Rheology Journal
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• 제12권1호
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• pp.77-81
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• 2000

Rheological behavior of thermoset/thermoplastic blends of epoxy/polyethersulphone (PES) was monitored during curing of the epoxy resin. During the isothermal curing of the mixture, a fluctuation in viscosity just before the abrupt viscosity increase was observed. This fluctuation is found to be due to the phase separation of PES from the matrix epoxy resin during the curing. The experimentally observed viscosity fluctuation is simulated with a simple two phase suspension model in terms of the increase in domain size. The viscosity profiles obtained experimentally at different isothermal curing temperatures are in good agreement with the predictions from the simple model taking into account the viscosity change due to the growth of PES domain and the network formation of the epoxy matrix.

• Elastomers and Composites
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• 제52권4호
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• pp.266-271
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• 2017

This study describes the influence of the amount of curing agent and curing temperature on the kinetics of polyurethane elastomers. The urethane prepolymer series was prepared by reacting toluene diisocyanate with polytetramethylene ether glycol at $80^{\circ}C$ for 1 h, and 4,4'-methylene bis(2-chloroaniline) was used as the curing agent. The ratio of the amine group of the curing agent to the isocyanate group of the urethane prepolymer was controlled from 0.85 to 1.05 at curing temperatures ranging from 80 to $120^{\circ}C$. The curing rate of the urethane prepolymer was monitored by observing the change in heat flow during the curing process using differential scanning calorimetry (DSC). As either the content of curing agent or the curing temperature was higher, the conversion rate to the polyurethane elastomer was high. The DSC results were compared with those obtained from using real-time FT-IR.

• International Journal of Precision Engineering and Manufacturing
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• 제1권1호
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• pp.33-41
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• 2000

Fiber reinforced metal laminates(FRMLs) were new type of hybrid materials. FRMLs consist of high strength metals(Al 5052-H34) and laminated fiber with structural adhesive bond. The effect of resin mixture ratios on the fatigue crack propagation behavior and mechanical properties of aramid fiber reinforced aluminum composites was investigated. The epoxy, diglycidylether of bisphenol A(DGEBA), was cured with methylene dianiline(MDA) with or without an accelerator(K-54). Eight kinds of resin mixture ratio were used for the experiment ; five kinds of FRMLs(1)(mixture of epoxy and curing agent) and three kinds of FRMLs(2)mixture of epoxy, curing agent and accelerator). The characteristic of fatigue crack propagation behavior and mechanical properties FRMLs(2) shows more effecting than that of FRMLs(1).

• 한국세라믹학회지
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• 제35권5호
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• pp.437-442
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• 1998

In order to investigate the mechanical properties of several fibers for reinforced cement these speciments with 2wol% of ARG and organic fibers were formed by vacuum extrusion process. After steam curing and autoclaving the flexural strength and the elastic modulus of FRC were measured. It was found that the ARG-FRC showed the elastic-brittle fracture behavior in both steam cured and autoclaved condition. And also the steam cured PP and PVA-FRC had elstic-plastic behavior but their ductility were reduced and changed to the elastic-brittle after autoclaving This change in mechanical behavior was found to be related to the thermal stablity of thes organic fibers.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 춘계학술대회 논문집
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• pp.177-181
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• 1995

Lead-acid battery is used widely as a power source in the automobile, industrial machines, folk lifts U.P.S etc. But this battery has man\ulcorner disadvantages such as heavy low energy density, environment problem etc. In this paper, we have studied the physicochemical and electrochemical properties of lead-acid battery positive plates with regard to the method of curing. It has been observed that curing conditions strongly influence electrode composition and electrchemical performance.

• 콘크리트학회논문집
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• 제20권5호
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• pp.543-548
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• 2008

프리캐스트 제품은 소요의 강도를 단기간에 얻기 위하여 일반적으로 상압 증기양생을 실시하며, 칼슘-실리케이트의 수열합성반응을 이용할 경우 1차 양생 이후에 오토클레이브 양생이라는 2차 양생도 실시하고 있다. 여기에서 제품의 강도발현에 커다란 영향을 미치는 양생 방법의 경우, 2차 양생 방법에 대한 연구는 각종 연구로 부터 수열반응에 적합한 조건이 구명되는 등 많은 연구가 수행되었으나, 1차 양생 방법에 대한 검토는 아직 미비한 실정이며 생산업체별로 양생 방식을 달리하여 제품을 생산하고 있어 제품의 소요강도 획득에 문제점을 가지고 있다. 이에 본 연구에서는 수열합성 경화체에 있어서 보다 높은 강도를 얻기 위한 1차 양생 방법에 대한 자료를 얻고자 실험적 연구를 수행하였다. 즉 수열합성 경화체에 있어서 1차 양생 방법을 건식과 건/습식 그리고 습식으로 실시한 후에 각각의 시험체에 대하여 수화특성을 알아보기 위하여 SEM, XRD, DT-TGA 및 porosimeter 시험을 실시하였으며, 강도 특성을 알아보기 위하여 압축강도 시험을 실시하였다. 측정 결과, 1차, 2차 양생 후 각 양생조건에 따른 시험체의 압축강도는 건/습식 양생조건이 강도발현에 유리한 것으로 나타났으며, 그 차이는 크지 않은 것을 알 수 있었다. 수화도 분석을 위한 SEM, XRD 및 DT-TGA의 측정 결과, 건/습식 양생조건의 경우가 건식과 습식 양생조건에 비해 가장 많이 수화가 진행된 것을 알 수 있었고, porosimeter의 측정 결과에 있어서도 건/습식 양생조건이 강도특성에 유리한 공극특성을 갖는 것으로 나타났다.