Effect of CNT as a Nucleating Agent on Cell Morphology and Thermal Insulation Property of the Rigid Polyurethane Foams

Ahn, WonSool,Lee, Joon-Man American Scientific Publishers 2015 Journal of Nanoscience and Nanotechnology Vol.15 No.11

Thermal Decomposition Kinetics of Polyurethane Elastomers Prepared with Different Dianiline Chain Extenders

( Wonsool Ahn ) 한국고무학회 2016 엘라스토머 및 콤포지트 Vol.51 No.2

Thermal decomposition kinetics for two different types of polyurethane elastomers prepared with 2,2``-dichloro- 4,4``-methylenedianiline (MOCA) and 3,5-dimethyl-thiotoluenediamine (Ethacure-300), based on PTMG/TDI isocyanate prepolymer, were studied using non-isothermal thermogravimetric analysis (TGA). Thermograms were obtained and analyzed using Friedman (FR) and Kissinger-Akahira-Sunose (KAS) methods for activation energy, Ea. The results obtained showed that decomposition reaction of both samples was observed similarly to occur through three different stages, i.e., initial stage with vaporization of low molecular weight materials, second stage of urethane linkage decompositions, and later stage of polyol segment decompositions. However, activation energy values at each stage for the sample cured with Ethacure- 300 was much lower than those for the sample with MOCA, exhibiting relatively lower thermal stability for the sample with Ethacure-300 than that with MOCA.

A Study on Magnetic Property Improvement of Rubber Magnets for Heat Loss Reduction of a Refrigerator

( Wonsool Ahn ),( Haakil Lee ),( Ji Soo Ha ) 한국고무학회 2016 엘라스토머 및 콤포지트 Vol.51 No.1

For improving the heat loss of a refrigerator around door gasket, it is very important to reduce the amount of rubber magnet used, of which thermal conductivity is much higher than the plastics, and enhancing the magnetic properties of rubber magnet itself is crucial for this. In the present study, therefore, a relationship between the optimum conditions of rubber magnet fabrication process and raw material compositions in the ferrite powder/CPE binder compounds was investigated for finding a way to enhance the magnetic properties of rubber magnet. Magnetic attraction forces of a sample rubber magnet was measured as function of distance, and thermal properties of the sample ferrite powder/CPE binder compound were analyzed with TG/DTA thermal analyzer. As a results, a rubber magnet strip with enhanced magnetic properties was expected to be fabricated, of which raw material compound was prepared by compounding with higher ferrite magnetic powder concentration.

Open-Cell Rigid Polyurethane Foam Using Lithium Salt of 12-Hydroxystearic acid as a Cell Opening Agent

WonSool Ahn(안원술),Joon-Man Lee(이준만) 한국고분자학회 2018 폴리머 Vol.42 No.6

일반적인 독립 셀 구조의 경질 폴리우레탄 폼을 제조하기 위한 조성비에 12-hydroxystearic acid의 리튬 염(Li-12HSA)을 셀 개방제로 사용하여 개방 셀 구조를 가지는 경질 폴리우레탄 폼을 제조하기 위한 연구를 진행하였다. Li-12HSA는 일반적인 폴리우레탄 폼 조성에 사용되는 실리콘 계면활성제를 기유로 사용하여 합성되었고 기유내에 나노스케일로 잘 분산되도록 하였다. 실험의 결과로서 약 1.0 phr의 Li-12HSA가 사용된 샘플 폼에서 거의 100%의 셀 개방률을 나타내어 Li-12HSA가 적절한 셀 개방제로 사용될 수 있음을 보여주었다. 이는 폼 생성 과정중에서 폴리우레탄의 주사슬에 Li-12HSA가 곁사슬로 형성되어 셀 개방에 크게 영향을 미치기 때문인 것으로 생각되었다. 또한 생성된 개방 셀 구조의 경질 우레탄 폼은 독립셀 구조의 폴리우레탄 폼의 기계적 특성을 크게 저해하지 않으면서도 바람직한 셀 크기, 벌크 밀도, 및 열전도 특성을 가지는 것으로 나타났다. Cell opening characteristics of a polyurethane foam (PUF) with conventional formulation for a closed-cell rigid PUF was studied using lithium salt of 12-hydroxystearic acid (Li-12HSA) as a cell-opening agent. The cell-opening agent, Li-12HSA, was properly prepared in the surfactant silicone oil, in which it existed as uniformly distributed in nanoscale. Cell opening content of nearly 100% could be obtained for the sample with ca. 1.0 phr of Li-12HSA. As the results, it showed that a fully open-cell rigid PUF could be obtained by introducing Li-12HSA as a new reactive cell opener, having a functional group which is able to form a bulky flexible side-chain on PU main chains. Furthermore, the formed open cell rigid PUF showed desirable cell size, bulk density, and thermal conductivity without severe loss of mechanical properties compared to those of the closed-cell PUF which was made without Li-12HSA.

Life Time Prediction Using Accelerated Ageing Test for a CR/CB Rubber Composite

( Wonsool Ahn ),( Hyung Seok Lee ) 한국고무학회 2017 엘라스토머 및 콤포지트 Vol.52 No.4

The tensile strength (TS) and elongation-at-break (EB) loss of a CR/CB rubber composite sample prepared for the automotive parts were measured after accelerated thermal ageing at temperatures of 100, 120, 140, and 150℃. The change in TS was observed to be linear from the master curve prepared using the time-temperature superposition-principle (TTSP). An Arrhenius type of shift factor, a_T was used to predict the life time of the sample, and a plot of ln a_T vs. 1/T was also shown to be linear. The activation energy (E_a) of the sample was calculated as 70.30 kJ/mole from the Arrhenius plot. The expected life time of the sample was predicted at the given operating conditions by applying Arrhenius analysis. Assuming the E_a value was constant at lower operating condition, life time of the sample was calculated as 2.3 years when the life limit was set as time to reach the 20% decrease of the initial TS value at operating temperature of 40℃.

Cure Kinetics of a Bisphenol-A Type Vinyl-Ester Resin Using Non-Isothermal DSC

( Wonsool Ahn ) 한국고무학회 2018 엘라스토머 및 콤포지트 Vol.53 No.1

In the current research, the curing kinetics of a mixture system consisting of a Bisphenol-A type vinyl ester resin and styrene monomer was studied. Methylethylketone peroxide and cobalt octoate were used as the polymerization initiator and accelerator respectively. Thermograms with several different heating rates were obtained using non-isothermal differential scanning calorimetry. Activation energy values analyzed by the Flynn-Wall-Ozawa isoconversional method showed a three-step change with conversion α: a slight decrease initially for α < 0.1, a constant value of 47.9 kJ/mol in the range 0.1 < α < 0.7, and a slow increase for 0.7 < α. When assuming a constant activation energy of 47.9 kJ/mol, an autocatalytic model of the Sestak-Berggren equation was considered as the proper mathematical model of the conversion function, indicating an overall order of 1.2.

Elastomers and Composites : Research Papers ; A Study on Reaction Kinetics of PTMG/TDI Prepolymer with MOCA by Non-Isothermal DSC

( Wonsool Ahn ),( Seong Ho Eom ) 한국고무학회 2015 엘라스토머 및 콤포지트 Vol.50 No.2

A study on reaction kinetics for a PTMG/TDI prepolymer with 2,2``-dichloro-4,4``-methylenedianiline (MOCA), of which formulations may be generally used for fabricating high performance polyurethane elastomers, was peformed using non-isothermal differential scanning calorimetry (DSC). A number of thermograms were obtained at several constant heating rates, and analysed using Flynn-Wall-Ozawa (FWO) isoconversional method for activation energy, E a and extended-Avrami equation for reaction order, n. Urea formation reaction of the present system was observed to occur through the simple exothermic reaction process in the temperature range of 100 ~ 130oC for the heating rate of 3 ~ 7 oC/ min. and could be well-fitted with generalized sigmoid function. Though activation energy was nearly constant as 53.0±0.5 kJ/mol, it tended to increase a little at initial stage, but it decreases at later stage by the transformation into diffusion-controlled reaction due to the increased viscosity. Reaction order was evaluated as about 2.8, which was somewhat higher than the generally well-known 2nd order values for the various urea reactions. Both the reaction order and reaction rate explicitly increased with temperature, which was considered as the indication of occurring the side reactions such as allophanate or biuret formation.

A Study on Transformation of Dynamic DSC Results into Isothermal Data for the Formation Kinetics of a PU Elastomer

( Wonsool Ahn ) 한국고무학회 2018 엘라스토머 및 콤포지트 Vol.53 No.2

The present study examines the transformation of dynamic DSC data into the equivalent isothermal data for the formation kinetics of a polyurethane elastomer. The reaction of 2'-dichloro-4,4'-methylenedianiline (MOCA) with a PTMG/ TDI-based isocyanate prepolymer was evaluated. DSC measurement was performed in the dynamic scanning mode with several different heating rates to obtain the reaction thermograms. Then, the data was transformed into the isothermal data through a procedure based on Ozawa analysis. The main feature of this procedure was the transformation of (α-T)β curves from dynamic DSC into (α-t)T curves using the isoconversional (t-T)α diagram. Validity was discussed for the relationship between the dynamic DSC data and the transformed isothermal results.

IIR을 개질제로 이용한 EPDM 고무의 환경내구성 향상에 관한 연구

안원술(WonSool Ahn) 계명대학교 낙동강환경원 2007 環境科學論集 Vol.12 No.1

A study on the enhancement of environmental durability of EPDM rubber materials for the aerator membrane was performed using IIR as a modifier. A conventional EPDM rubber formulation (Sample A) was evaluated as having about 26.0 wt% of oil derivatives from the chloroform immersion test. These oils would be gradually and continuously deleted from the aerator membrane when directly exposed to a waste-water or chemically corrosive fluids, making the membrane less flexible and the performance worse. To improve this, an IIR rubber was utilized as the modifier for a low-ENB type of EPDM rubber formulation having lower oil content (Sample B). The environmental durability of the Sample B was expected to be greatly enhanced compared to Sample A, fully satisfying the specifications for the target aerator membrane, while the mechanical and performance properties such as elongation, tensile strength, and air bubble size, etc. were still maintained as in Sample A. Furthermore, TG/DTG analysis of Sample B showed that there would be partial compatibility between IIR and EPDM. It also showed that the initial degradation temperature would be somewhat increased, and from which, the enhanced compatibility among the components and, thereby, more enhanced environmental durability could be expected.

비등온 TGA를 이용한 고무복합재료의 수명 예측

안원술(WonSool Ahn),최슬기(Seul-Ki Choi) 한국산학기술학회 2014 한국산학기술학회 학술대회 Vol.- No.-

자동차 엔진 부품용으로 많이 사용되는 ACM 고무 샘플에 대하여 150, 160, 170, 및 180oC의 등온 상 태에서 시간에 따른 압축영구줄음율(CS)과 열중량감소율을 측정하여 상관관계를 구하고, 이를 비등온 TGA를 이용하는 Toop의 해석방법에 이용하여 사용온도에서의 수명을 예측하고자 하였다. 노화촉진 시험으로부터 측정된 중량감소율는 CS에 대하여 선형적으로 변화하는 것이 관찰되었으며, 이로부터 CS 40%에 이르는 시간을 재료의 수명시간으로 했을 때 중량감소에 의한 전환율은 4.2%로 나타났다. TGA 곡선으로부터 Flynn-Wall-Ozawa법에 의하여 전환율 4.2%에서의 활성화에너지는 120.2 kJ/mol 로 계산되었으며, 이를 Toop의 해석법에 적용하였을 때의 예측수명은 사용온도 120oC에서 약 9,700 시 간으로 계산되었다.