Axisymmetric squeezing dynamics of resin droplet with surface tension and its numerical solution

하근동 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.12

We investigate the 2D axisymmetric quasi-static dynamics of a UV-curable optically clear resin droplet squeezed between two parallel glass walls using a static force. The radial spreading speed and resulting radial spread are examined using an analytical derivation and a numerical discretized approximation including the effect of the surface tension. Under a boundary condition, the vertical downward velocity of the glass wall is determined by the static force and capillary pressure, and a pressure discontinuity occurs across the air-liquid interface. The capillary pressure is estimated from the Young-Laplace equation. A numerical approximate solution is then derived from the governing equations to obtain a discretized set of linear equations to serve as an alternative theoretical solution. A 2D axisymmetric section with a staggered grid is adopted for a pressure-based segregated velocity-pressure coupled solution process using the SIMPLE algorithm. The change in the rheological properties due to the UV-curing effect is then added to the squeezing dynamics solution with an arbitrary initiation time and the power amplitude of the UV curing. According to a few rheological test results for different UV powers, the relationship between the UV energy (calculated using the UV power) and the resin viscosity is confirmed. The numerical solution is validated, and both theoretical solutions are compared with the experimental results of several squeezing tests with and without UV curing.

에폭시/폴리옥시프로필렌 디아민계의 경화 반응속도 및 동역학 특성 분석

황광춘(Guang Chun Huang),이종근(Jong Keun Lee) 한국고분자학회 2011 폴리머 Vol.35 No.3

비스페놀 A 에폭시 수지와 폴리옥시프로필렌 디아민 경화제계의 경화 반응속도를 시차주사열량계을 이용하여 승온 및 등온 경화조건에서 조사하였다. 승온실험에서는 Ozawa와 Kissinger법을 이용하여 다양한 가열속도에서 얻어진 발열피크의 이동으로부터 활성화 에너지를 구하였다. 또한 등온실험에서 얻어진 데이터는 자촉매 효과를 고려한 Kamal의 속도모델로 분석하였으며, 그 결과 경화반응 초기의 속도우세 구간에서 실험데이터와 잘 맞았다. 반응 후기의 확산우세 구간에서는 확산효과를 적용하여 경화의 전체과정을 기술하였다. 또한 동역학분석을 이용하여 경화 후 저장 탄성률과 가교점간의 평균분자량을 측정하였다. The cure kinetics of a bisphenol A epoxy resin and polyoxypropylene diamine curing agent system are investigated in both dynamic and isothermal conditions by differential scanning calorimetry (DSC). In dynamic experiments, the shift of exothermic peaks obtained at different heating rates is used to obtain activation energy of overall cure reaction based on the methods of Ozawa and Kissinger. Isothermal DSC data at different temperatures are fitted to an autocatalytic Kamal kinetic model. The kinetic model is in a good agreement with the experimental data in the initial stage of cure. A diffusion effect is incorporated to describe the later stage of cure, predicting the cure kinetics over the whole range of curing process. Also, dynamic mechanical analysis is performed to evaluate the storage modulus and average molecular weight between crosslinkages.

광중합 복합레진의 중합초기 동적 점탄성의 변화

김민호,이인복 대한치과보존학회 2009 Restorative Dentistry & Endodontics Vol.34 No.5

본 연구의 목적은 새로 개발한 점탄성 측정기를 사용하여 수종의 광중합 복합레진의 초기 동적 점탄성 변화를 측정하는 것이다. 본 연구에 사용된 점탄성 측정기는 세 부분으로 구성되었다. 첫째, 시편이 놓여지는 parallel plates; 둘째, DC 모터와 크랭크로 이루어진 회전진동전단변형 (Oscillatory shear strain)을 발생시키는 부분; 셋째, 전자기적 토크센서를 이용한 응력 측정 부분으로 구성되었다. 본 점탄성 측정기는 최대 2 Ncm의 토크를 측정할 수 있으며, 광중합기의 스위치는 컴퓨터와 연동하여 데이터 획득을 시작할 때 동시에 켜지도록 하였다. 본 연구에서는 시판 중인 6종의 광중합 복합레진 [Z-100 (Z1), Z-250 (Z2), Z-350 (Z3), DenFil (DF), Tetric Ceram (TC), Clearfil AP-X (CF)]을 사용하였다. 점탄성 측정기를 사용하여 동적 회전전단실험을 시행하였다. 직경 3 mm인 유리막대로 구성된 parallel plates 사이에 14.2㎣의 복합레진을 적용시켰으며, 6 Hz의 진동수와 0.00579 rad의 진폭으로 변형을 가하고 발생된 응력을 측정하였다. 광중합이 시작됨과 동시에 측정이 시작되었으며, 광중합 후 10초 동안 점탄성의 변화를 관찰하였다. 각 복합레진에 대해 5 회 반복하여 측정하였고, 실험은 에서 진행되었다. 측정된 변형-응력 곡선으로부터 복소전단탄성계수 G*, 저장전단탄성 계수 G', 손실전단탄성 계수 G"를 구하였고 G*가 10 MPa에 이르는 시간을 구하였다. 각 재료의 복소전단탄성계수 G*와 10 MPa에 이르는 시간에 대해 일원분산분석 (One-way ANOVA)과 사후검정 (Tukey 검정)을 시행하였다 (α= 0.05). 결과는 다음과 같다. 1. 본 연구를 위해 제작한 점탄성 측정기는 광중합 복합레진의 중합 초기 10초 동안의 동적 점탄성 변화를 신뢰성 있게 측정 할 수 있었다. 2. 모든 복합레진은 광조사 개시 후 초의 불응기를 지난 다음 급격한 전단탄성계수의 증가를 보였다. 3. 모든 복합레진은 광중합 10 초간 손실전단탄성계수보다 저장전단탄성계수의 높은 증가를 보였다. 4. 광중합 초기 10초 후 복소전단탄성계수 값은 로, Z-100이 가장 높았고, 그 다음 Clearfil, Z-250, Z-350, Tetric Ceram, DenFil의 순이었다. 5. 복소전단탄성계수가 10 MPa에 이르는 시간은 Z-100이 2.55초로 가장 빨랐고, DenFil이 4.06초로 가장 느렸다. The aim of this study was to measure the initial dynamic modulus changes of light cured composites using a custom made rheometer. The custom made rheometer consisted of 3 parts: (1) a measurement unit of parallel plates made of glass rods, (2) an oscillating shear strain generator with a DC motor and a crank mechanism, (3) a stress measurement device using an electromagnetic torque sensor. This instrument could measure a maximum torque of 2Ncm, and the switch of the light-curing unit was synchronized with the rheometer. Six commercial composite resins [Z-100 (Z1), Z-250 (Z2), Z-350 (Z3), DenFil (DF), Tetric Ceram (TC), and Clearfil AP-X (CF)] were investigated. A dynamic oscillating shear test was undertaken with the rheometer. A certain volume (14.2 ㎣) of composite was loaded between the parallel plates, which were made of glass rods (3 mm in diameter). An oscillating shear strain with a frequency of 6 Hz and amplitude of 0.00579 rad was applied to the specimen and the resultant stress was measured. Data acquisition started simultaneously with light curing, and the changes in visco-elasticity of composites were recorded for 10 seconds. The measurements were repeated 5 times for each composite at . Complex shear modulus G*, storage shear modulus G', loss shear modulus G" were calculated from the measured strain-stress curves. Time to reach the complex modulus G* of 10 MPa was determined. The G* and time to reach the G* of 10 MPa of composites were analyzed with One-way ANOVA and Tukey's test (α = 0.05). The results were as follows. 1. The custom made rheometer in this study reliably measured the initial visco-elastic modulus changes of composites during 10 seconds of light curing. 2. In all composites, the development of complex shear modulus G* had a latent period for seconds immediately after the start of light curing, and then increased rapidly during 10 seconds. 3. In all composites, the storage shear modulus G" increased steeper than the loss shear modulus G" during 10 seconds of light curing. 4. The complex shear modulus of Z1 was the highest, followed by CF, Z2, Z3, TC and DF the lowest. 5. Z1 was the fastest and DF was the slowest in the time to reach the complex shear modulus of 10 MPa.

Diminotetrefluorophenoxycyclotriphosphazene에 의해 경화시킨 에폭시 수지의 동적점탄성과 열적성질

尹興洙 慶一大學校 1999 論文集 Vol.16 No.5

1, 1-diamino-3, 3, 5, 5-tetrafluorophenoxycyclotriphosphazene was prepared from hexachlorocy-clotriphosphazene and used for the curing agent of phenol novolak type and diglycidyl ether bisphenol A. The effect of the curing agent on the dynamic viscoelastic properties, flame proofing, and heat resistance of the cured epoxy resins were investigated and compared with those for the epoxy resins cured with aliphatic amine and aromatic anime. The epoxy resin cured by 1, 1-diamino-3, 3, 5, 5-tetrafluorophenoxycyclotriphosphazene showed the highest storage modulus and glass transition temperature when cured at postcure temperature, 190℃ for 6 hours. The epoxy resins of phenol novolak type cured with 1, 1-diamino-3, 3, 5, 5-tetrafluoro-phenoxycyclotriphosphazene showed superior flame proofing to those of diglycidyl ether bisphenol A, aliphatic amine, and aromatic amine. Particularly 1, 1-diamino-3, 3, 5, 5-tetrafluorophenoxycy-clotriphopphazene was an effective curing agent for epoxy resins to enhance the storage modulus, flame proofing, and resistance to heat.

슬러지 양생 장치의 건조특성에 관한 연구

정호윤(H. Y. Jung),박재성(J. S. Park),권지혁(J. H. Kwon),이종훈(J. H. Lee),이연원(Y. W. Lee) 한국동력기계공학회 2006 한국동력기계공학회 학술대회 논문집 Vol.- No.-

Recently, we have many problems on the process of the sewage sludge. In past, the sewage sludge was treated by reclaimed land or thrown away in the sea. But these methods caused environmental pollution, Today, many researchers are studying various methods for reducing its volume. One of these method, this study is to reduce the moisture of sewage sludge and to solidify it using a dryer and curing equipment. In this research, we investigated about design parameter and operation condition of the equipment. The curing equipment reduces the percentage of water content from 30% of dryer to 10%. So, we have to study the curing characteristics and performance of curing equipment. For example, there are internal flow characteristics and change of the percentage of water content. And we investigated the change of data at outlet along the initial condition, temperature, humidity and air flow. Using this data, we achieve the experimental results of curing efficiency by each geometry and operating condition. And we also investigated numerical analysis of internal flow using CFD code. This research is basic study for optimal design of the curing equipment.

Effect of isocyanate crosslinkers blocked with amine derivatives on rheological and crosslinking characteristics of automotive clearcoats

Young-Gun June,정인조,Tae Hee Lee,하미란,Seung Man Noh,정현욱 한국유변학회 2021 Korea-Australia rheology journal Vol.33 No.1

Isocyanate crosslinkers with blocking agents based on various amine derivatives were newly synthesized for automotive clearcoat applications. Amine-based blocking agents were prepared by varying the alkyl substituent attached on both sides of the main nitrogen atom (named DEA, DiPA, NtBEA, and NtBiA) to modify their deblocking feature in blocked isocyanates (BIs) and curing reaction under thermal curing conditions. Curing properties of clearcoats containing amine-based BIs were characterized at the normal curing temperature of 150°C and were compared with those by the commercialized BI, Desmodur® PL350. The dissociation ability of the amine-based BIs was interpreted using the density functional theory (DFT) simulation under their optimized geometric configurations. The urethane reaction between isocyanate group in BIs and hydroxyl group in a hydroxyl-functionalized polyol binder within clearcoats was confirmed from the OH stretching absorbance data via Fourier-transform infrared (FT-IR) spectrometer. The real-time crosslinking dynamics of various clearcoats with amine-based BIs were comprehensively investigated using rotational rheometer and rigid-body pendulum tester. The surface mechanical properties of fully-cured clearcoat films were measured by nano-indentation and nano-scratch testers to address the crosslinked network formation caused by amine-based BIs. It is demonstrated that the amine-based BIs could be favorably applied to thermal curing process of clearcoats, based on their reactivity and curing performance.

승온 반응속도식을 이용한 LED용 실리콘 렌즈의 경화공정해석

송민재,홍석관,박정연,이정원,김흥규,Song, Min-Jae,Hong, Seok-Kwan,Park, Jeong-Yeon,Lee, Jeong-Won,Kim, Heung-Kyu 한국금형공학회 2014 한국금형공학회지 Vol.8 No.2

Silicone is recently used for LED chip lense due to its good thermal stability and optical transmittance. In order to predict residual stress which causes optical briefringence and mechanical warpage of silicone, finite element analysis was conducted for curing process during silicone molding. For analysis of curing process, a dynamic cure kinetics model was derived based on the differential scanning calorimetry(DSC) test and applied to the material properties for finite element analysis. Finite element simulation result showed that the slow cure reduced abrupt reaction heat and it was predicted decrease of the residual stress.

동적 패턴 생성기를 이용한 3차원 미세 구조물의 경화특성

하영명(Y. M. Ha),최재원(J. W. Choi),안대건(D. K. Ahn),이석희(S. H. Lee),하창식(C. S. Ha) 한국정밀공학회 2005 한국정밀공학회 학술발표대회 논문집 Vol.2005 No.10월

Microstereolithography(MSL) has evolved from the stereolithography technique, and is also based on a light-induced layer-stacking fabrication. Although integral MSL allows the manufacture of a complete layer by one irradiation only, there is a problem related with shape precision due to the light-intensity distribution of focused image. In this study, we developed the integral MSL apparatus using Digital Micromirror Device (DMDTM, Texas Instruments) as dynamic pattern generator. It is composed of Xenon-Mecury lamp, optical devices, pattern generator, precision stage, controllers and the control program. Also, we have studied curing depth and width of photocurable resin according to the change of exposure energy.

Preparation and Properties of Barium Titanate Nanopowder/Epoxy Composites

Chandradass, J.,Bae, Dong-sik TaylorFrancis 2008 Materials and manufacturing processes Vol.23 No.2

<P> This article is focused on the preparation of barium titanate nanopowder/epoxy composites and studying the effect of barium titanate nanopowder on improving mechanical and thermal characteristics of the epoxy polymer. Composites are prepared by dispersing barium titanate nanopowder in epoxy resin and, subsequently, cross-linking by using diamino diphenyl methane (DDM) curing agents. Synthesis of barium titanate nanopowder/epoxy composites is carried out for different concentrations (1, 3, and 5 by weight) of barium titanate nanopowder at high temperature. High-temperature curing (HTC) involves mixing the resin-nanopowder solution followed by DDM hardener and curing at 120°C. Tensile, flexure, and impact results showed a maximum value of 72.7 MPa, 2.98 GPa, and 2 J/cm, respectively. DSC analysis revealed that curing occurs at low temperature in the presence of barium titanate nanopowder. Thermogravimetry analysis (TGA) showed the increased thermal stability in the nanoparticle filled epoxy composites as compared with the pure epoxy counterparts. Dynamic mechanical analysis (DMA) revealed, maximum storage modulus of 6400 MPa and glass transition temperature of 154°C for 3 wt% barium titanate nanopowder.</P>

이산화탄소 반응경화 시멘트 블록양생기 내부 유동의 CFD 해석 연구

이종명,임민혜,안광옥,김창범 한국폐기물자원순환학회 2023 한국폐기물자원순환학회지 Vol.40 No.6

Research on reducing greenhouse gas emissions from cement production, including carbon capture and storage (CCS), is actively ongoing. Many studies have focused on using captured carbon dioxide to enhance the carbonation reaction in cement production. The carbonation reaction of calcium silicate-based cement (CSC) is expected to be primarily applied to blocks because of challenges such as rebar corrosion. This study employed computational fluid dynamics (CFD) analysis to examine the internal flow and carbonation reactions on the mold surface within a carbonation reactor designed for block production using CSC cement. The analysis results revealed that the rotational flow inside the reactor was well formed, effectively dispersing gas outward due to the rotation. This ensured that, despite the injection of high concentrations of carbon dioxide, a consistent carbon dioxide concentration and flow distribution were maintained adjacent to the mold. These findings affirm that the design of the carbonation reactor was well executed. Furthermore, it was anticipated that the carbonation reaction between carbon dioxide and carbonate would start across the entire mold surface after 150 seconds inside the carbonation reactor. This study established an analysis model for the internal flow and reactions within the carbonation reactor, specifically for carbonating carbon dioxide. This provides a foundational basis for appropriately designing the reactor, even when its size and shape undergo modifications. The findings from this research are expected to contribute to future studies focused on improving the performance of carbonation cement and blocks.