광경화 아크릴레이트 단량체의 복합경화 특성

배진우(Jin Woo Bae),정재현(Jae Hyun Jung),왕혁식(Hyuck Sik Wang),김석현(Seok Hyeon Kim),김일중(Il Joong Kim),김익재(Ik Jyae Kim),송기국(Kigook Song) 한국고분자학회 2017 폴리머 Vol.41 No.2

광경화와 열경화능을 가진 아크릴레이트 단량체를 사용하여 광경화-열경화 또는 열경화-광경화의 순서에 따른 경화속도 변화를 고찰하였다. Isocyanatoethyl acrylate(ICEA)와 2-hydroxyethyl methacrylate(HEMA) 처럼 광경화와 열경화 메카니즘이 다른 단량체 혼합물에 먼저 UV에 의한 광반응을 진행한 후, 2차로 열경화를 하는 복합경화시스템을 조사하였다. 이 경우 1차 광경화에 의해 고분자 사슬이 형성되면, 2차로 열경화에 의해 우레탄 반응에 참여하는 관능기들이 고분자 사슬에 묶이게 되어 열경화에 의한 우레탄 반응을 더 높은 온도에서 진행하여야 하며, 전환율도 낮아지는 것을 확인하였다. 반면에, 같은 조성의 혼합물에 열경화를 먼저 진행하고 광경화를 하는 복합경화의 경우에는 열경화에 의해 우레탄 아크릴레이트 단량체가 먼저 생성된 후, 단량체 양 말단에서 반응이 진행되어 빠르게 광경화 반응이 진행되었다. Dual curing systems of acrylates with thermo- and photo-reactions were studied to understand the effect of curing sequence on the curing reaction kinetics. A combined curing system that photochemical reaction with UV light followed by thermal cure was applied to acrylate monomer mixtures such as isocyanatoethyl acrylate (ICEA) and 2-hydroxyethyl methacrylate (HEMA). In such case, the polymer chain was formed by the first photo-curing and, then the functional groups participating in the urethane reaction were bound to the polymer chain, so that the urethane reaction by the thermal curing should be carried out at a higher temperature and the conversion rate was low. On the other hand, in the case of a dual curing process in which the photo-curing proceeded after the thermal curing, the urethane acrylate monomer was first formed by the thermal reaction, and then the faster photo-reaction proceeded at both ends of the monomer.

Multi-step cure kinetic model of ultra-thin glass fiber epoxy prepreg exhibiting both autocatalytic and diffusion-controlled regimes under isothermal and dynamic-heating conditions

김이찬,민현성,홍성용,Mei Wang,선한나,박인경,최혁렬,구자춘,문형필,Kwang J Kim,서종환,남재도 한국유변학회 2017 Korea-Australia rheology journal Vol.29 No.3

As packaging technologies are demanded that reduce the assembly area of substrate, thin composite laminate substrates require the utmost high performance in such material properties as the coefficient of thermal expansion (CTE), and stiffness. Accordingly, thermosetting resin systems, which consist of multiple fillers, monomers and/or catalysts in thermoset-based glass fiber prepregs, are extremely complicated and closely associated with rheological properties, which depend on the temperature cycles for cure. For the process control of these complex systems, it is usually required to obtain a reliable kinetic model that could be used for the complex thermal cycles, which usually includes both the isothermal and dynamic-heating segments. In this study, an ultra-thin prepreg with highly loaded silica beads and glass fibers in the epoxy/amine resin system was investigated as a model system by isothermal/dynamic heating experiments. The maximum degree of cure was obtained as a function of temperature. The curing kinetics of the model prepreg system exhibited a multi-step reaction and a limited conversion as a function of isothermal curing temperatures, which are often observed in epoxy cure system because of the rate-determining diffusion of polymer chain growth. The modified kinetic equation accurately described the isothermal behavior and the beginning of the dynamic-heating behavior by integrating the obtained maximum degree of cure into the kinetic model development.

UV-curing kinetics and performance development of <i>in situ</i> curable 3D printing materials

Kim, Ye Chan,Hong, Sungyong,Sun, Hanna,Kim, Myeong Gi,Choi, Kisuk,Cho, Jungkeun,Choi, Hyouk Ryeol,Koo, Ja Choon,Moon, Hyungpil,Byun, Doyoung,Kim, Kwang J.,Suhr, Jonghwan,Kim, Soo Hyun,Nam, Jae-Do Elsevier 2017 European polymer journal Vol.93 No.-

<P><B>Abstract</B></P> <P>As three-dimensional (3D) printing technology is emerging as an alternative way of manufacturing, the high resolution 3D printing device often requires systems such as drop jetting printing of <I>in situ</I> UV-curable photopolymers. Accordingly, the key issue is process control and its optimization to ensure dimensional accuracy, surface roughness, building orientation, and mechanical properties of printed structures, which are based on the time- and temperature-dependent glass transition temperature (<I>T<SUB>g</SUB> </I>) of the resin system under UV-curing. In this study, the UV-cure kinetics and <I>T<SUB>g</SUB> </I> development of a commercially available UV-curable acrylic resin system were investigated as a model system, using a differential scanning photocalorimeter (DPC). The developed kinetic model included the limited conversion of cure that could be achieved as a maximum at a specific isothermal curing temperature. Using the developed model, the <I>T<SUB>g</SUB> </I> was successfully described by a modified DiBenedetto equation as a function of UV curing. The developed kinetic model and <I>T<SUB>g</SUB> </I> development can be used to determine the 3D printing operating conditions for the overlay printing and <I>in situ</I> UV curing, which could ensure high-resolution and high-speed manufacturing with various UV-curing materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> UV-cure kinetic analysis were applied to a commercial Multi-jet 3D printing material. </LI> <LI> The developed kinetic model included the limited conversion of cure by temperature. </LI> <LI> The <I>T<SUB>g</SUB> </I> was described by a modified DiBenedetto equation as a function of UV curing. </LI> <LI> The developed kinetic model showed an excellent agreement to isothermal experiments. </LI> <LI> The overlay printing time for each isothermal temperature was determined. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Curing Behavior of 4,4'-Diglycidyloxybiphenyl with p-Phenylene Diamine Derivatives

Arinola Isa Olamilekan,여현욱 한국고분자학회 2020 Macromolecular Research Vol.28 No.10

To expand the applicability of 4,4'-diglycidyloxybiphenyl (BP), the simplest liquid crystalline epoxy derivative, the curing reaction mechanism with pphenylenediamine (p-PDA) derivatives under various stereoscopic conditions was investigated through kinetic analyses. Specifically, curing factors such as the starting temperature, heat, and activation energy were studied and analyzed. In particular, the effect of steric hindrance of the hardeners on the mechanism of curing reactions was explored by analyzing isothermal kinetics. It was found that the larger steric hindrance of the curing agents induced the slower curing reaction, and the contribution of the reduction in the self-catalytic curing was more pronounced than the SN2 reaction. To determine the optimized curing conditions, cured BP materials were fabricated and their glass-transition temperatures and thermal conductivities, which significantly improved over general-purpose epoxy resins owing to the characteristics of the liquid crystal, were investigated.

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.

열경화성 수지 재료를 이용한 광학 렌즈 제조공정에서 렌즈 변형에 대한 수축률이 영향에 관한 연구

박시환 한국금형공학회 2022 한국금형공학회지 Vol.16 No.3

In order to reduce the manufacturing costs of the glass lens, it is necessary to manufacture a lens using a UV curable resin or a thermosetting resin, which is a curable material, in order to replace a glass lens. In the case of forming a lens using a thermosetting material, it is necessary to form several lenses at once using the wafer-level lens manufacturing technologies due to the long curing time of the material. When a lens is manufactured using a curable material, an error in the shape of the lens due to the shrinkage of the material during the curing process is an important cause of defects. The major factors for these shape errors and deformations are the shrinkage and the change of mechanical properties in the process of changing from a liquid material during curing to a solid state after complete curing. Therefore, it is necessary to understand the curing process of the material and to examine the shrinkage rate and change of physical properties according to the degree cure. In addition, it is necessary to proceed with CAE for lens molding using these and to review problems in lens manufacturing in advance. In this study, the viscoelastic properties of the material were measured during the curing process using a rheometer. Using the results, Rheological investigation of cure kinetics was performed. At the same time, The shrinkage of the material was measured and simple mathematical models were created. And using the results, the molding process of a single lens was analyzed using Comsol, a commercial S/W. In addition, the experiment was conducted to compare and verify the CAE results. As a result, it was confirmed that the shrinkage rate of the material had a great influence on the shape precision of the final product.

Isoconversional Cure Kinetics of Modified Urea-Formaldehyde Resins with Additives

Park, Byung-Dae 경북대학교 농업과학기술연구소 2012 慶北大農學誌 Vol.30 No.1

As a part of abating formaldehyde emission of urea-formaldehyde resin, this study was conducted to investigate the rmalcure kinetics of both neat and modified urea-formaldehyde resins using differential scanning calorimetry. Neat urea-formaldehyde resins with three different formaldehyde/urea mol ratios (1.4, 1.2 and 1.0) were modified by adding three different additives (sodium bisulfite, sodium hydrosulfite and acrylamide) at two different levels (1 and 3wt%). An isoconversional method at four different heating rates was employed to characterize thermal cure kinetics of these urea-formaldehyde resins to obtain activation energy () dependent on the degree of conversion (). The values of neat urea-formaldehyde resins (formaldehyde/urea = 1.4 and 1.2) consistently changed as the increased. Neat and modified urea-formaldehyde resins of these two F/U mol ratios did show a decrease of the at the final stage of the conversion while the of neat urea-formaldehyde resin (formaldehyde/urea = 1.0) increased as the increased, indicating the presence of incomplete cure. However, the change of the values of all urea-formaldehyde resins was consistent to that of the Ea values. The isoconversional method indicated that thermal cure kinetics of neat and modified urea-formaldehyde resins showed a strong dependence on the resin viscosity as well as diffusion control reaction at the final stage of the conversion.

Absorption kinetics of superabsorbent polymers (SAP) in various cement-based solutions

Kang, S.H.,Hong, S.G.,Moon, J. Pergamon Press ; Elsevier Science Ltd 2017 Cement and concrete research Vol.97 No.-

<P>A new modified tea-bag method with various cement-based solutions is used to investigate the absorption kinetics of superabsorbent polymer (SAP) in concrete with low water to cement ratio (W/C). It includes a centrifugal process to efficiently remove the excess solution that can cause inaccurate absorption measurements. Various cement-based artificial pore solutions are prepared by dissolving ions in cement filtrates and considering the influence of silica fumes and polycarboxylate-ether type superplasticizers. Depending on the monovalent ion concentrations under the given Ca concentration of the filtrate, the absorption kinetics is drastically altered. This result underlines the risk of underestimating the absorption capacity of SAP in concrete. The suggested method and prepared solutions can be used to reasonably and efficiently determine the amount of required extra water for internal curing. Furthermore, the investigated ion-dependent characteristics will enhance our understanding of the absorption kinetics and contribute to the development of hydrogel products for concrete. (C) 2017 Published by Elsevier Ltd.</P>

일정온도 상승률 열분석법을 이용한 수지 경화 모델 개발

엄문광,황병선,Eom, Mun-Gwang,Hwang, Byeong-Seon,Isaac M. Daniel 한국기계연구원 1999 硏究論文集 Vol.29 No.-

In general, manufacturing processes of thermosetting composites consist of mold filling and resin cure. The important parameters used in modeling and designing mold filling are the permeability of the fibrous preform and the viscosity of the resin. To consolidate a composite, resin cure or chemical reaction plays an essential role. Cure kinetics. Therefore, is necessary to quantify the extent of chemical reaction or degree of cure. It is also important to predict resin viscosity which can change due to chemical reaction during mold filling. There exists a heat transfer between the mold and the composite during mold filling and resin cure. Cure kinetics is also used to predict a temperature profile inside composite. In this study, a new scheme which can determine cure kinetics from dynamic temperature scaning was proposed. The method was applied to epoxy resin system and was verified by comparing measurements and predictions.

광반응성 아크릴레이트 단량체의 반응성비가 경화필름의 기계적 물성에 미치는 영향

왕혁식(Hyuck Sik Wang),이승혁(Seung Hyuk Lee),부석형(Seok Hyeong Bu),김홍두(Hong Doo Kim),송기국(Kigook Song) 한국고분자학회 2020 폴리머 Vol.44 No.3

본 연구에서는 두 종류 이상의 아크릴레이트 단량체를 공단량체로 경화시킬 때, 단량체의 상대적 반응성비에 따른 사슬의 가교구조 변화를 예측하고, 경화된 필름의 기계적 물성 변화를 설명하였다. 올리고머/희석제/응집제로 구성된 아크릴 혼합물에서 희석제 butyl acrylate만 butyl methacrylate로 대체하여 경화한 필름의 기계적 물성이 인장강도는 5배 이상, 그리고 modulus는 200배 이상 증가하는 것을 보여주었다. 필름의 기계적 물성에 직접적으로 큰 영향을 주지 못하는 첨가제인 희석제의 구조를 단순히 아크릴레이트에서 메타크릴레이트로 바꾸어 필름의 강도를 크게 향상시킬 수 있는 현상을 아크릴 반응의 경화 kinetics와 이에 영향을 받은 사슬의 가교구조 변화를 바탕으로 설명하였다. When two or more types of acrylate monomers with a comonomer are cured, the change in the cross-linking structure of the chain according to the relative reactivity ratio of the monomers was predicted, and the mechanical properties of the cured film were described. In the oligomer/diluent/coagulant mixture, the mechanical properties of the film cured by replacing only butyl acrylate with butyl methacrylate showed that the ultimate strength increased by more than 5 times and the modulus by 200 times. The phenomenon that the strength of the film was significantly improved by simply changing the structure of the diluent, which is an additive that does not directly affect the mechanical properties of the film, from acrylate to methacrylate, is a result of curing kinetics of the acrylic reaction and the cross-linking structure of the chains affected by it.