Poly(4-methylstyrene) as an Internal Standard Candidate for Quantification of Rubber Components in Environmental Samples Using Pyrolysis-Gas Chromatography/Mass Spectrometry

( Eunji Chae ),( Sung-seen Choi ) 한국고무학회 2024 엘라스토머 및 콤포지트 Vol.59 No.4

An internal standard is essential in quantitative analysis to enhance the accuracy and precision. In the analysis of tire wear particles in environmental samples, a pyrolysis technique such as pyrolysis-gas chromatography/mass spectrometry is commonly employed to quantify rubber components. Deuterated polymers such as deuterated polyisoprene are usually used as internal standards. However, their high cost necessitates the search for alternative standards. In this study, we propose poly(4-methylstyrene) (PMS) as a viable new internal standard. We compare calibration curves constructed using the peak areas of the pyrolysis products from natural rubber with those corrected using the pyrolysis products of PMS. The main pyrolysis products of PMS include 4-methylsyrene, 1,3-bis(4-methylphenyl) propane, 2,4-bis(4-methylphenyl) butene, and 2,4-bis(4-methylphenyl) penta-1,4-diene. The use of the dimeric pyrolysis products of PMS as the internal standard results in an improved correlation coefficient of R² > 0.990.

Characteristics in Size Distributions and Morphologies of Wear Particles Depending on Types of Abrasion Testers

( Eunji Chae ),( Seong Ryong Yang ),( Sung-seen Choi ) 한국고무학회 2023 엘라스토머 및 콤포지트 Vol.58 No.2

Abrasion tests of an SBR compound were conducted using four different types of abrasion testers (cut and chip, Lambourn, DIN, and LAT100). The abrasion test results were analyzed in terms of size distributions and morphologies of the wear particles. Most wear particles were larger than 1000 μm. The wear particle size distributions tended to decrease as the particle size decreased. Except for the Lambourn abrasion test, the wear particles smaller than 212 μm were rarely generated by the other three abrasion tests, implying that small wear particles were produced through friction by introducing talc powder. Shapes of the wear particles varied depending on the abrasion testers. The wear particles generated from the Lambourn abrasion tester had stick-like shapes. The cut and chip abrasion test showed a clear abrasion pattern, but the DIN abrasion test did not show any specific abrasion pattern. The Lambourn and LAT100 abrasion tests showed irregular abrasion patterns.

Extraction Methods of Organic Components from Rubber Composites and Analysis of the Extract Using Gas Chromatography/Mass Spectrometry

( Eunji Chae ),( Sung-seen Choi ) 한국고무학회 2019 엘라스토머 및 콤포지트 Vol.54 No.3

Rubber articles contain various organic additives such as antidegradants, curing agents, and processing aids. It is important to extract and analyze these organic additives. In this paper, various extraction methods of organic additives present in rubber composites were introduced (solvent extraction, Soxhlet extraction, headspace extraction, and solid-phase microextraction), and the extracts were characterized using gas chromatography/mass spectrometry (GC/MS). Solvent and Soxhlet extractions are easy-to-perform and commonly used methods. Efficiency of solvent extraction varies according to the type of solvent used and the extraction conditions. Soxhlet extraction requires a large volume of solvent. Headspace sampling is suitable for extracting volatile organic compounds, while solid-phase extraction is suitable for extracting specific chemicals. GC/MS is generally used for characterizing the extract of a rubber composite because most components of the extract are volatile and have low molecular weights. Identification methods of chemical structures of the components separated by GC column were also introduced.

EFFECTS OF ZINC ACETATE DIHYDRATE ON ZNO THIN FILM PREPARED BY SOL-GEL ASSISTED SPIN COATING METHOD

Eunji Chae,Hyejeong Jeong,Seongjae Boo 한국신재생에너지학회 2011 AFORE Vol.2011 No.-

Preparation of Rubber Particulates for Micro Dust Study using Cryogenic Crushing

( Eunji Chae ),( Chae Eun Son ),( Sung-seen Choi ) 한국고무학회 2019 엘라스토머 및 콤포지트 Vol.54 No.4

Cryogenic crushing techniques have been employed for recycling waste rubber articles and for extracting residual organic additives present in rubber samples. Rubber particulate derived from tire tread abrasion is one of the key components of road dust. Therefore, in this work, we prepared rubber particulates using a cryogenic crusher and characterized their shapes as well as size distributions according to the type of rubber. The rubber particulates exhibited uneven surfaces with the presence of some small pieces. The order of the particle size distribution was observed to be: NR > BR > SBR. Subsequently, carbon black was added; this led to a decrease in the particle size and the shape becoming rougher. The crushed particulates of the carbon black-filled samples comprised agglomerated shapes of small pieces, which were similar in shape to that of wear debris in tire tread. It was discovered that crosslink density was one of the principal factors that led to the formation of small crushed particulates. The small particulates obtained by cryogenic crushing can be utilized as model rubber particulates for researching micro dust.

Analysis of Peroxide Curing Agents in EVA Compounds and Vulcanizates

( Eunji Chae ),( Sung-seen Choi ) 한국고무학회 2020 엘라스토머 및 콤포지트 Vol.55 No.1

Poly(ethylene-co-vinyl acetate) compounds and vulcanizates containing dicumyl peroxide (DCP) (HD) were pre­pared, and the curing agent and reaction products were analyzed using gas chromatography/mass spectrometry (GC/MS). Samples containing trially cyanurate (TAC) and DCP (HDT) were also prepared and analyzed. Some raw DCP were decom­posed in the injector region of GC to produce acetophenone. DCP was detected in the HD compound but was not observed in the HD vulcanizate, and instead acetophenone and 2-phenyl-2-propanol were detected. Both DCP and TAC were observed in the HDT compound but not in the HDT vulcanizate, where acetophenone and 2-phenyl-2-propanol were detected. Thus, some of the DCP decomposed during the compounding process. The formation mechanism for acetophe­none and 2-phenyl-2-propanol during the crosslinking reaction was identified, and differences in the crosslinking reactions of HD and HDT compounds were discussed.

Characterization of Chlorinated NR using Pyrolytic Technique

( Eunji Chae ),( Sung-seen Choi ) 한국고무학회 2020 엘라스토머 및 콤포지트 Vol.55 No.4

Vehicle wiper blades are typically treated with chlorine to lower their friction coefficient with the windshield surface. In this study, a chlorinated, natural rubber (NR) vehicle wiper blade was characterized using a pyrolytic technique. Unchlorinated and chlorinated wiper blades were pyrolyzed and the pyrolysis products were analyzed using gas chromatography/ mass spectrometry (GC/MS). Besides isoprene and dipentene, the other principal pyrolysis products such as 1,5,8- p-menthatriene (MTT) and p,α-dimethylstyrene (DMS) were observed. The MTT and DMS ratios did not vary for the chlorinated nor unchlorinated samples when the entire rubber lip of the wiper blade was pyrolyzed. However, when only the lip surface of the wiper blade rubber was pyrolyzed (via scratching with a knife) the relative ratios of the chlorinated sample were much greater than those of the unchlorinated sample. As MTT is produced from the conjugated backbone of chlorinated NR that forms through HCl elimination during initial pyrolysis, and DMS is generated by the dehydrogenation of MTT, these two products could be used as markers for detecting chlorinated NR.

Building Calibration Curve for Py-GC/MS Analysis of SBR/BR Blend Rubber Compounds

( Eunji Chae ),( Sung-seen Choi ) 한국고무학회 2020 엘라스토머 및 콤포지트 Vol.55 No.4

A calibration curve is needed to determine the SBR and BR blend ratio of SBR/BR blend rubber compounds using pyrolysis-gas chromatography/mass chromatography (Py-GC/MS) or Py-GC. In general, a calibration curve is obtained using reference SBR/BR vulcanizates with various blend ratios. In this study, the calibration curves were obtained using reference samples made of rubber solutions and were compared to those plotted using the reference SBR/BR vulcanizates. Calibration curves using variations of 1,3-butadiene/styrene, 4-vinylcyclohexene (VCH)/styrene, 2-phenylpropene (PhP)/butadiene, PhP/VCH, 4-phenylcyclohexene (PhCH)/butadiene, and PhCH/VCH ratios with the BR content were examined for the suitability. We found that the calibration curves obtained using the mixed rubber solution references (1,3- butadiene/styrene and PhP/butadiene) could replace those constructed using the reference SBR/BR vulcanizates. The calibration curves of 1,3-butadiene/styrene and PhP/butadiene obtained using the raw references can be used for the determination of the SBR/BR blend ratios by applying some correction factors.

A Retrospective and Prospective Follow-up Study of Psychological Distress in the Danwon High School Survivors of the Sewol Ferry Disaster

EunJi Kim,HeeSun Nam,HakBeom Kim,Unsun Chung,SoHee Lee,JeongHo Chae 대한신경정신의학회 2018 PSYCHIATRY INVESTIGATION Vol.15 No.3

Objective-We monitored a group of students from Danwon High School who survived the Sewol ferry disaster for 27 months to examine the course of their psychological symptoms. Methods-We performed a chart review at the Danwon High School Mental Health Center at the following time points (T): 9 months (T1), 12 months (T2), and 15 months (T3) after the disaster. Additionally, we performed a follow-up review at 27 months (T4). Subjects completed the ‘State’ section of the State-Trait Anxiety Inventory for Children, the Center for Epidemiological Studies-Depression assessment, the Child Report of Post-traumatic Symptoms, and the Inventory of Complicated Grief. Data from the 32 subjects who completed all four assessments were used in the statistical analyses. Results-Scores of psychological variables tended to increase until T2 and then slowly decreased until T4. The severity of anxiety and complicated grief symptoms changed significantly over time, but the severity of depression and posttraumatic stress symptoms did not. Conclusion-We found that the symptoms of anxiety and complicated grief reported by Sewol ferry survivors from Danwon High School were exacerbated at the first anniversary of the disaster, but these symptoms subsided after the students graduated from high school.

공공연구성과 실용화를 위한 데이터 기반의 기술 포트폴리오 분석: 빅데이터 및 인공지능 분야를 중심으로

전은지 ( Eunji Jeon ),이채원 ( Chae Won Lee ),류제택 ( Jea-tek Ryu ) (사)한국빅데이터학회 2021 한국빅데이터학회 학회지 Vol.6 No.2

Since small and medium-sized enterprises fell short of the securement of technological competitiveness in the field of big data and artificial intelligence (AI) field―core technologies of the Fourth Industrial Revolution, it is important to strengthen the competitiveness of the overall industry through technology commercialization. In this study, we aimed to propose a priority related to technology transfer and commercialization for practical use of public research results. We utilized public research performance information, improving missing values of 6T classification by deep learning model with an ensemble method. Then, we conducted topic modeling to derive the converging fields of big data and AI. We classified the technology fields into four different segments in the technology portfolio based on technology activity and technology efficiency, estimating the potential of technology commercialization for those fields. We proposed a priority of technology commercialization for 10 detailed technology fields that require long-term investment. Through systematic analysis, active utilization of technology, and efficient technology transfer and commercialization can be promoted.