• Membrane Journal
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• v.33 no.6
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• pp.369-376
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• 2023

In this study, the alternative to the energy-intensive conventional vacuum distillation process, an eco-friendly and energy-efficient pervaporation separation was employed in 1,2 hexane diol/water (HDO/water) mixture. The crosslinked PVA-glutaraldehyde was coated inside the alumina hollow fiber membrane (Al-HF). In the HDO/IPA pervaporation separation, optimization of the membrane concerning PVA/GA ratio, curing temperature, and pervaporation operating condition were performed. In the long-term stability test, the sustainable pervaporation separation performance giving flux in the range of 1.90~2.16 kg/m²h, and water content in permeate was higher than 99.5% (separation factor = 68) was obtained from the PVA/GA (molar ratio = 0.08, curing temperature = 80℃) coated Al-HF membrane from HDO/water (25/75, w/w, %) mixture at 40℃. Therefore, this work provides potential and inspiration for PVA-based membranes to mitigate excessive energy requirements in HDO/water separation by pervaporation.

• Journal of Korean Society of Forest Science
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• v.63 no.1
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• pp.12-20
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• 1984

This research was performed to estimate the properties of particleboard based on the press time and temperature which was made of chip of larch that grows in Korea. The results in this study were as follows: 1) Even though the chips, 1:1-35 ratio between length and thickness, are relatively bad condition, the surface smoothness that can easily spread the adhesive evenly and thoroughly and bonding ability of chips can give proper physical properties. 2) It shows more mechanical properties at the press time of 10 min. in MOR (Modulus of Rupture), MOE (Modulus of Elasticity) and SHA (Screw Holding Ability). 3) It is not significant according to the press time 20 min. in MOR, IBS (Internal Bonding Strength) and SHA, for the reciprocal actions between the accelerating aging effect of chip and the softening effect of adhesion are occured. 4) IBS is rising according to the increasing temp at the press time of 10 min. Because it needs to transfer the plate heat to make the proper hardening temp. In the layer. 5) The heat treatment effects have greatly influenced the stahility of dimension by falling the absorption, anisotropy and inhomegenity. As a result of these the values of thickness and linear expansion ratio were respectively dropped by the increase of press temp and the time and so did absorption.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.39.1-39.1
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• 2010

겨울철 혹한지방에서의 차량운행 또는 여름철 혹서지방에서의 장시간 차량 운행시 차체를 구성하고 있는 강판에는 약 $-50^{\circ}C{\sim}150^{\circ}C$의 온도환경에 처하게 된다. 따라서 이러한 저온 고온 환경하에서 차체 충돌상품성 예측 및 충돌안전 설계를 위해 온도에 따른 차체 강판의 기계적 물성평가가 요구된다. 이를 위해 본 연구에서는 자동차용 충돌부재에 주로 쓰이는 HS440MPa, HS590MPa급 냉연 고장력 강판에 대해 $-60^{\circ}C{\sim}200^{\circ}C$의 온도범위로 저온 고온 인장시험을 수행 하였다. 각각의 인장시험 결과로부터 온도 별 항복강도, 인장강도, 연신율, 가공경화지수 등 기계적 물성 변화를 평가하였다. 저온 고온 인장시험은 ZWICK Z250 만능재료시험기를 사용하였고 KS5호 규격의 인장시편을 사용하였으며, 시편에 충분한 온도를 가하기 위하여 목표온도 도달 후 20분간 유지한 뒤 인장시험을 수행하였다. 인장시험결과 HS440MPa, HS590MPa급 두 강종 모두 온도가 낮아질수록 강도 및 연신율 등이 증가하였고, 온도가 증가할수록 강도 및 연신율 등 기계적 물성이 저하 되었다. 즉, 우리가 주로 평가해왔던 상온($25^{\circ}C$)에 비해 저온 고온 환경하에서는 강판의 기계적 물성 변화가 큰 것을 알 수 있다. 따라서 혹한 또는 혹서 지방 등 온도차이가 큰 운행환경하에서의 차체 강도 및 충돌안전성 확보를 위해 온도에 따른 강판의 정확한 물성평가가 필요하고 차체 설계시 온도에 따른 강도변화를 충분히 고려하여야 한다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.2
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• pp.94-99
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• 2018

The purpose of this study is to investigate the effect of combinations of different accelerators mixed on the early age strength development of concrete of 21 to 27MPa in the curing temperature of $10^{\circ}C$ compared with existing early strength agent. The present study was assessed the early strength development of combinations of three different accelerating admixtures with early strength type agent comparing to single accelerating admixture with early strength type agent. As a result of this study, the effect of $CaBr_2+NaSCN+DEA$ combination on strength development showed better than $CaBr_2$ or NaSCN alone with early strength type agent. Therefore, we observed that concrete using $CaBr_2+NaSCN+DEA$ combination with early strength agent was achieved 5MPa 12hours earlier than use of $CaBr_2$ or NaSCN alone.

• Polymer(Korea)
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• v.25 no.1
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• pp.78-89
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• 2001

Morphological changes of unsaturated polyester/polyvinylacetate semi-IPN were studied while the phase separation and the cure reaction occurred in a competing fashion. The light scattering and thermal analysis techniques were used to investigate the phase separation rates and mechanical properties resultantly induced by molecular diffusion of thermoplastic polymer during the curing process of thermosetting polymer. The reaction activation energy was calculated by using Flynn-Wall method and the semi-IPN structure exhibited various phase-separation morphological characteristics. When PVAc composition was 10 wt%, the phase separation was not observed during the curing reaction, but the phase separation occurred in a similar fashion to nucleation and growth(NG) mechanism at room temperature. On the other hand, when PVAc composition was over 11.65 wt%, the phase separation was generated in the middle of the curing process. Consequently, the phase separation seemed to influence the curing reaction rate, which was also supported by the changing activation energy with conversion and PVAc composition. Finally, the total scattered intensity was measured at various temperature, and subsequently the diffusion rates of phase separation R(${\beta}m$) were evaluated.

• Magazine of the Korea Concrete Institute
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• v.6 no.5
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• pp.203-212
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• 1994

The setting and hardening of concrete is accompanied by nonlinear temperature distribution caused by developing heat of cement hydration. This leads to tensile stresses that may exceed the strength of the young concrete, and cracks occur. In this present study, the heat of hydration characteristics are obtained from a study in which insulated concrete cubes were tested. Based on test results, concrete heat of hydration characteristics according to unit weight cement and flyash replacement quantity are determined, then employed in a numerical temperature analysis that consider both environmental interaction and concreting phases. The numerical results are performed by ADINA - T. The analytical results are in good agreement with experimental data.

• Journal of the Korean Society of Safety
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• v.19 no.4 s.68
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• pp.135-140
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• 2004

Wear mechanisms may be briefly classified by mechanical, chemical and thermal wear. A plane strain finite element method is used with a new material stress and temperature fields to simulate orthogonal machining with continuous chip formation. Deformation of the workpiece material is healed as elastic-viscoplastic with isotropic strain hardening and the numerical solution accounts for coupling between plastic deformation and the temperature field, including treatment of temperature-dependent material properties. Effect of the uncertainty in the constitutive model on the distributions of strait stress and temperature around the shear zone are presented, and the model is validated by comparing average values of the predicted stress, strain, and temperature at the shear zone with experimental results.

• Applied Chemistry for Engineering
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• v.17 no.1
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• pp.33-36
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• 2006

The kinetics of photopolymerization of urethane-acrylate oligomer which has many applications in photopolymerizable adhesives was analysed to investigate the influence of polymerization temperature and functionality of oligomer using the autocatalytic model. It was revealed that the maximum polymerization rate decreased as the polymerization temperature increased. The reaction rate constant, k, showed little change with the increase in polymerization temperature, while exponents m and n exhibited an increase. These results could be related to the diffusion and mobility restriction of reactive species during the cross-linking reaction. The decrease in photopolymerization rate with increase of temperature was mainly controlled by the reaction order n.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.2
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• pp.46-53
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• 2005

We have analyzed the temperature and humidity aging test results of a composite solid propellant. The temperature aging test was performed to evaluate the storage life of a propellant, while the humidity aging test could provide the hygroscopicity of Ammonium Perchlorate(AP) exposed to .elative humidity (RH) 10, 30, $50\%$ environment. A specimen was used in the temperature test, and a block of propellant from the actual motor was used in the humidity test. We report that the 4-month storing at 60 degree is equivalent to the 10-year 60 degree condition. The composite solid propellant with HTPB binder showed signs of hardening with time lapse but the effect of humidity up to RH $50\%$ was not noticeable.

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.117-124
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• 2006

The effects of binder content and recycling mixed waste plastics(PA) content on the workability, work life and hardening shrinkage of fresh polymer concrete using mixed waste plastics are examined. As a result, the workability of the polymer concretes using mixed waste plastics tend to improve with increasing binder content, PA content and filler content. The work life of the polymer concretes using mixed waste plastics is shortened with an increase in the initiator content and curing temperature. The length change of the polymer concretes using mixed waste plastics tend to increased with Increasing binder content and PA content. The result of the present research is expected to make a contribution to the recycling of final mixed waste plastics and the continuing efforts for the development of use of the recycled products are thought to expand the horizon for the recycling of the final mixed waste plastics.