Cure behaviors of vinyl ester resins with low profile thermoplastic additives and thermoplastic elastomers = 수축 억제용 열가소성 수지 및 열가소성 탄성체가 첨가된 열결화성 비닐 에스테르 수지의 경화 거동
서명 / 저자 Cure behaviors of vinyl ester resins with low profile thermoplastic additives and thermoplastic elastomers = 수축 억제용 열가소성 수지 및 열가소성 탄성체가 첨가된 열결화성 비닐 에스테르 수지의 경화 거동 / Myung-Sun Hong.
저자명 Hong, Myung-Sun ; 홍명선
발행사항 [대전 : 한국과학기술원, 1991].
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학술문화관(문화관) 보존서고

DCE 9113

휴대폰 전송






Vinyl ester was prepared from diglycidyl ether of bisphenol A based epoxy resin and methacrylic acid and then dissolved in styrene monomer at the mole ratio of vinyl ester/styrene=1/2. The cure reaction, a free radical growth crosslinking copolymerization, was performed in the presence of various kind of additives. The additives were poly(methyl methacrylate) [PMMA], poly(vinyl acetate) [PVAC] having function of low profile additive and vinyl terminated butadiene-acrylonitrile copolymer [VTBN] having function of toughening agent and poly (styrene-ethylene-butylene-styrene) block copolymer[S-EB-S], poly(styrene-isoprene-styrene) block copolymer[S-I-S] having function of thermoplastic elastomer. Those additives were characterized by compatibility and reactivity with vinyl ester resin. A series of experiments were performed to characterize the cure kinetics and cure behaviors of vinyl ester resins with various kind of additives. Differential scanning calorimeter(DSC) was used to investigate the rate of cure, the degree of cure and the vitrification time. It was also used to determine kinetic parameters and physical property such as glass transition temperature. The rate of cure passed through a maximum and then decreased as the degree of cure increased. The maximum value became smaller and its position shifted toward a longer cure time when the cure temperature became lower. Such behavior is similar to the autocatalytic reactions which often appeared in the condensation reaction. The reaction mixture was not completely cured under isothermal condition. And the final degree of cure increased along with cure temperature. It was due to the vitrification which occurs when the glass transition temperature approaches the cure temperature. Also the viscosity change with the cure time showed gelation point through which a liquid state transforms to rubbery state. Hence, the kinetic model was developed on the base of the phenomena of autocatalytic behavior, vitrification, and gelation. After the parameters in the kinetics model were determined through dynamic DSC result, the isothermal cure was predicted and then was compared with experimental results measured by DSC under isothermal condition. When the temperature was low, the predicted values deviated a little bit from the experimental data. However when the cure temperature was raised, the kinetic model could fit the isothermal DSC results very well. Especially it showed a better agreement in cure in which gelation was followed by vitrification. The gelation, and vitrification times were calculated from the kinetic model. Time-Temperature-Transformation (TTT) cure diagram was plotted by using the kinetic model. The time taken to reach gelation and vitrification was shorter for neat vinyl ester resin than for vinyl ester resins with additives. In the vinyl ester resins with reactive additives, namely VTBN rubber and S-I-S elastomer, the more additive content, the shorter gelation time but the longer vitrification time. Structural evolutions were investigated through FTIR. Copolymer between vinyl ester and styrene monomer formed through electron donor-acceptor mechanism. In the initial stage of cure, vinyl ester was cured faster than styrene monomer. However, as cure reaction proceeded, styrene monomer was cured more than vinyl ester because of the diffusion control due to the increase of viscosity. In vinyl ester resins with reactive VTBN rubber or S-I-S block copolymer, styrene caused a chain extention or a grafting reaction between vinyl ester resin and VTBN rubber or vinyl ester resin and S-I-S block copolymer. The young's modulus measured by Instron of neat vinyl ester resin was greater than that of vinyl ester resins with additives. The elongation and toughness of vinyl ester resin with VTBN rubber were the greatest. The qualitative extent of volumetric shrinkage was obtained from first normal stress difference measured by Rheometric dynamic spectrometer. The shrinkage could be controlled by using the additives. The order of efficiency in shrinkage control was found to be VTBN rubber>S-I-S block copolymer>PMMA>S-EB-S block copolymer>PVAC. Examination through Scanning electron microscope revealed the nodular structure on tensile fracture surface of neat vinyl ester resins and demonstrated that fracture proceeded around nodulus. Separated phase of dispersed small particles between styrene and PMMA was shown in the vinyl ester resin with PMMA. And tensile fracture surface showed a rippling and steady crack propagation which may be considered taking place on the PMMA grafted by styrene within the separated phase. Whereas, the tensile fractography of the vinyl ester resins with PVAC showed similar morphology to neat vinyl ester resins. The tensile fractography of vinyl ester resin with VTBN showed matrix-rubber debonding, crazing and cavitation within rubber particles. In the vinyl ester resins with S-I-S block copolymer, the cracks of ring shape were developed. An unusal fractography has been observed in vinyl ester resin with S-EB-S. The tensile fractography shows stick-slip tear which parallel surface features extends in the direction of crack propagation. These linear features appear to by lying on "tracks". The additives act as the topological resistance against migration or the reactive sites for active species. According to whether the reaction between vinyl ester network and additives arose from covalent bonding or physical interaction, the network showed the different of structural evolution, which resulted in the difference of morphology and the consequent mechanical properties. The additives having covalent bonding with vinyl ester resin were more efficient in the improvement of shrinkage control and mechanical properties than the physically dispersed additives.

비닐에스테르수지를 에폭시계 비스페놀A형 디글리시딜에스테르 와 메타아크릴산으로 합성하여 이를 가교제인 스티렌 단량체에 1 대 2 의 몰비로 용해 시켰다. 비닐에스테르수지의 경화반응은 비닐에스테르 와 스티렌의 자유라디칼에 의한 가교결합반응으로 경화시 체적의 수축현상이 야기 된다. 본 연구에서는 수축현상을 억제하고 기계적성질을 증가시키기 위해 여러 종류의 첨가제가 함유된 비닐에스테르수지의 경화거동을 조사하였다. 첨가제로는 수축억제 기능을 가진 열가소성 폴리메타아크릴레이트, 폴리비닐아세테이트 수지와 수축억제 기능이외에 기계적 성질을 증가시키는 VTBN 고무와 폴리(스티렌-에틸렌/부틸렌-스티렌), 폴리(스티렌-이소프렌-스티렌) 삼중블럭공중합체와 같은 열가소성탄성체를 사용 하였다. 이와같은 첨가제가 함유된 비닐에스테르수지의 경화거동은 미분시차열분석기(DSC),점도계,푸리에변환적외선분광기(FTIR),광산란(Light Scattering), 주사전자현미경(SEM),RDS,DMA,인장시험기를 사용하여 분석되었고 이들 분석에서 비닐에스테르수지의 자유라디칼에 의한 가교결합 반응시 젤화,유리질화, 및 자동촉매반응과 유사한 현상이 관찰되어 이들 현상을 기초로한 경화거동의 새로운 모델식을 제시하였다. 또한 일반적인 경우와 달리 반응모델식의 상수들을 비등온열분석수치값(Dynamic DSC data)에서 구하여 이 모델식으로부터 등온수치값(Isothermal values)을 유추하여 실제 실험에서 얻어진 등온수치값과 비교하였다. 그 결과 모델식에서 유추된 값과 실험값은 젤화와 유리질화가 일어나는 영역에서 비교적 잘 일치 되었다. 이 결과로부터 여러 온도범위에서 젤화, 유리질화 시간을 예측 할수있는 시간-온도-전이 경화도형(TTT Cure Diagram)을 작성 하였다. 비닐에스테르수지의 경화반응은 비닐에스테르의 비닐기와 스티렌 단량체간의 자유라디칼에 의한 전자이동 반응으로 반응 초기에는 비닐에스테르의 소모속도가 스티렌 단량체의 소모속도보다 빨랐으나 반응이 진행되면서 점도가 증가함에 따라 분자이동이 용이한 스티렌 단량체의 소모속도가 빨랐다. 첨가제가 포함된 비닐에스테르수지의 경화속도는 순수한 비닐에스테르수지의 경화속도에 비해 느렸으며 VTBN고무나 폴리(스티렌-이소프렌-스티렌) 블럭공중합체와 같이 반응성 관능기를 지닌 첨가제가 함유된 비닐에스테르수지는 다른 단순한 첨가제가 함유된 비닐에스테르수지보다 젤화 속도는 빨랐지만 유리질화 속도는 느렸다. 또한, 반응성의 첨가제는 연신율, 내충격강도, 수축억제등의 기여도가 높았으며 이들의 기여도는 VTBN고무 > 폴리(스티렌-이소프렌 -스티렌)공중합체 > 폴리메타아크릴레이트> 폴리(스티렌-에틸렌/부틸렌-스티렌)공중합체> 폴리비닐아세테이트 순이었다. 이와같은 비닐에스테르수지의 수축억제와 기계적성질향상에 기여하는 이들첨가제들의 차이는 첨가제와 비닐에스테르수지와의 혼합도및 결합양상 - 화학적결합 또는 물리적 분산 - 에 기인하였으며 이들은 가교결합에의해 경화된 비닐에스테르수지의 구조및 형태에 영향을 미쳤다. 본 연구에서 비등온 모델식으로부터 열경화성수지의 가공공정에 중요한 변수인 여러 온도범위에서 등온하의 경화속도, 젤화시간, 유리질화시간을 예측할수있었고 비닐에스테르수지의 기계적성질을 개선하고 수축을 억제하기 위해서는 단순히 물리적으로 분산되는 첨가제보다는 화학적으로 결합을 이루는 첨가제가 효율적임을 알수있었다.


청구기호 {DCE 9113
형태사항 xxi, 254 p. : 삽도 ; 26 cm
언어 영어
일반주기 저자명의 한글표기 : 홍명선
지도교수의 영문표기 : In-Jae Chung
지도교수의 한글표기 : 정인재
학위논문 학위논문(박사) - 한국과학기술원 : 화학공학과,
서지주기 Reference : p. 243-249
주제 Block copolymers
Thermoplastic composites
경화 --과학기술용어시소러스
블록 공중합 --과학기술용어시소러스
열가소성 탄성체 --과학기술용어시소러스
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