분자 접합을 통한 강판/플라스틱 복합재료의 계면 접합력 향상

학위논문(박사) -- 서울대학교대학원 : 공과대학 재료공학부, 2023. 2. 안철희.강판/플라스틱 복합 재료는 복합재의 무게를 효과적으로 줄임과 동시에 고강성, 내피로성, 내충격성 등의 다양한 장점뿐 아니라 열과 진동 및 소음 차폐와 같은 다기능적 특성을 나타내어 오랜 기간 주목 받아왔다. 이러한 특색들은 강판/플라스틱 복합 재료에 대한 수요를 증가시키고 있으며, 에너지 위기 기간 동안 경량화가 시급히 대두되고 있는 자동차 산업에서 특히 수요가 증가하고 있다. 그러나 상용화된 강판/플라스틱 복합 재료는 미국의 MSC 사에서 개발된 Smartsteel® 제품이 유일하며, 개발 필요성에 비하여 관련 연구는 매우 미흡한 실정이다. 강판/플라스틱 복합 재료 개발에 있어 가장 도전적인 핵심 요소는 강판과 플라스틱간 계면 접합이다. 구조재 목적으로 활용하기 위해서는 견고하고 지속 가능한 계면 접합 특성이 요구된다. 기판의 표면 요철에 흡착되는 기존의 물리적 접합 방식은 온도, 습도 혹은 응력과 같은 외부 조건에 의한 계면 접합력 저하와 계면에서 발생하는 박리 현상으로 인하여 내구성 및 활용성이 낮은 결함이 존재한다. 강판과 플라스틱의 높은 접합 특성 유도를 위하여 레이저 용접 및 사출 성형을 통한 직접 결합과 같은 새로운 기술들이 최근 개발되고 있으나, 높은 비용과 다양한 재료에 대한 적용 가능성이 낮다는 한계로 인하여 여전히 널리 활용되지 못하고 있다. 계면 접합 특성을 향상시키기 위해서는 강판/플라스틱 계면에 대한 충분한 이해가 필수적이다. 계면 접합 특성에 영향을 미치는 요인은 일반적으로 플라스틱의 점도 (젖음성), 기판의 표면 조도, 물리적 및 화학적 상호 작용의 네 가지 유형으로 분류된다. 이러한 요인들 중, 플라스틱의 젖음성과 기판의 표면 조도에 의한 영향은 복합 재료의 제작 방식 선정을 통하여 용이하게 조절 가능하다. 본 연구에서는 열 압착 공정을 통하여 플라스틱을 강판 표면 요철 내 완전히 흡착시켜 계면 접합력을 향상시켰으며, 강판 및 플라스틱의 표면 처리 혹은 개질을 통하여 계면간 물리적, 화학적 상호 작용을 증진하였다. 본 연구의 2단원에서는 계면 접합 특성 향상을 위하여 플라스틱 표면의 물리적, 화학적 개질을 진행하였다. 플라스틱 표면 화학의 조절을 위한 자외선/오존 처리 혹은 주 사슬 내 극성 작용기가 도입된 공중합체 층의 도입 전략을 채택하였다. 두 전략 모두에서 접합 특성이 크게 증가하였으며, 이러한 전략을 기반으로 후속 연구를 진행하였다. 3단원에서는 열 압착 공정간 화학적 공유 결합 형성이 가능한 반응성 작용기를 강판과 플라스틱 표면에 각각 도입하여 접합 특성 향상을 유도하였다. 반응성 작용기로는 1차 아민과, 말레산 무수물을 적용하였으며, 선정한 모든 플라스틱 후보군에서 접합 특성이 크게 향상됨을 확인하였다. 접합 특성 향상의 원인으로 추정되는 세 가지 유형의 메커니즘을 제안하였으며 본 연구에서는 이를 분자 접합이라고 명명하였다. 4단원에서는 강판/플라스틱 복합 재료의 산업적 응용 가능성을 향상시키고자, 공정 단순화와 용접이 가능한 복합 재료 개발을 동시에 진행하였다. 연구 진행 과정에서 높은 접합 특성과 응집력을 나타낸 카보닐 작용기 함유 플라스틱 후보군들의 비교 평가를 통하여, 표면 개질 없이도 분자 접합을 통한 높은 접합 특성 발현이 가능한 폴리케톤이 최적 플라스틱으로 선별되었다. 강판의 경우, 90 % 이상의 접합 특성을 유지하면서 80 % 이상 표면 처리 시간을 단축하였다. 또한, 슈퍼엔지니어링 플라스틱인 PEEK를 플라스틱 코어층으로 활용하여 고 접합특성 및 내열성을 가지는 복합 재료를 개발하였다. 최종적으로, 기계화학을 통하여 전도성 필러를 플라스틱 표면에 흡착시켰으며, 이와 강섬유 메쉬의 복합 활용을 통하여 용접이 가능한 복합 재료를 개발하였다. 본 연구에서 개발된 분자 접합을 기반으로 한 고 접합 특성의 강판/플라스틱 복합 재료는 경량화를 요하는 다양한 산업 분야에 응용 가능한 충분한 잠재력을 보유하고 있다고 판단된다.Steel/plastic composites (SPCs) have attracted much attention for a long time since they display multifunctional characteristics such as thermal insulation, reduction in noise, vibration, and harshness (NVH) as well as multifarious advantages of high rigidity, fatigue resistance, and impact resistance while significantly reducing their weight. These advantages increase the demand for the employment of SPCs, especially in the automobile industry where weight reduction is an urgently leading issue during the period of energy crisis. To the best of our knowledge, the commercially available SPC is the only Smartsteel® developed by Material Sciences Corporation (US), and unfortunately, related researches are insufficient compared to the need for development. The most challenging key factor in the development of SPCs is the interfacial adhesion between steel and plastic. For an actual structural material, robust and sustainable adhesion is required. Conventional physical adhesion which permeates to the roughness of the substrate causes a deterioration in durability and applicability because of a decrease in interfacial adhesion due to external conditions such as temperature, humidity, and stress and also the occurrence of a peeling effect at the interface. Recently, several emerging techniques such as laser welding and direct bonding by injection molding have been developed for attaching steel and plastic. However, the wide application of these techniques is still thwarted because of their high cost and limitations in adopting various materials. For enhancing the interfacial adhesive properties, an impeccable understanding of the steel/plastic interface is essential. Factors that affect the interfacial adhesion are generally classified into four types: the viscosity (wettability) of plastic, the surface roughness of the substrate, and physical /chemical interaction. Among those factors, the viscosity (wettability) of plastic and surface roughness can be easily handled by the manufacturing method. Interfacial adhesion is enhanced by completely adsorbing plastic onto the surface roughness of steel via the hot-press process. Besides, physical and chemical interaction at the interface is mostly improved through surface treatment or modification of each substrate. In chapter 2, chemical and physical modification of the plastic surface was conducted to improve interfacial adhesion between steel and plastic. Physico-chemical treatment of the plastic surface and the introduction of a copolymer layer which has a polar functional group on the main chain of plastic were adopted for modifying the surface chemistry. The adhesion strength was greatly increased in both strategies, and these strategies were developed further for follow-up study. In chapter 3, for improving the interfacial adhesion between the steel and the plastic, functional groups capable of forming a covalent bond under the hot-press process were introduced onto both surfaces of the steel plate and the plastic film. The primary amine and maleic anhydride were applied as reactive functional groups. The adhesion strength was significantly enhanced in all plastic candidates. Three types of presumable adhesion mechanisms were proposed called molecular adhesion in this study. In chapter 4, both process simplification and development of weldable SPCs were conducted for improving the industrial applicability of SPCs. Carbonyl-containing plastic candidates were examined and polyketone which exhibited high adhesive properties via molecular adhesion without surface modification was singled out. The processing time of the steel surface was also effectively reduced by more than 80 % while maintaining adhesive properties above 90 %. Moreover, SPC with remarkably high adhesive properties and thermal resistance was developed using polyetheretherketone as the plastic core layer. The conductive fillers were embedded in the plastic surface through mechano-chemistry, and the steel fiber mesh was also adopted for the development of weldable SPCs. In summary, we believe that SPCs with molecular adhesion have sufficient potential to be applied in various industrial fields requiring weight reduction.Chapter1. Introduction 1 1.1. Steel/Plastic Composites for Weight Reduction 2 1.2. Interfacial Adhesion 4 1.3. State-of-The-Art in Adhesion Techniques for SPCs 11 1.4. Research Objectives 14 1.5. References 18 Chapter2. Chemical/Physical Modification of Plastic Surface and Understanding Adhesive Properties Between Steel and Plastic 22 2.1. Introduction 23 2.2. Experimental 27 2.3. Results and Discussion 34 2.4. Conclusion 46 2.5. References 47 Chapter3. Development of Interface Treatment to Enhance Adhesive Properties in Steel/Plastic Composites 49 3.1. Introduction 50 3.2. Experimental 54 3.3. Results and Discussion 61 3.4. Conclusion 81 3.5. References 82 Chapter4. Development of Steel/Plastic Composites with High Adhesive Properties and Industrial Applicability via Molecular Adhesion 84 4.1. Introduction 85 4.2. Experimental 89 4.3. Results and Discussion 97 4.4. Conclusion 119 4.5. References 120박

바이오 기반 다이올을 이용한 폴리에스터아마이드 수지 개발

학위논문 (석사)-- 서울대학교 대학원 : 공과대학 재료공학부, 2019. 2. 안철희.The growing interest in renewable resource-based feedstock chemicals and polymeric materials has promoted numerous studies in bio-sources. According to the current global production of bioplastics in 2017, PET and polyamide are the top two engineering plastics worldwide. PET exhibits disadvantages due to relatively low physical strength and Tg. One way to modify PET to yield a higher Tg and better mechanical properties is to combine polyesters and polyamides. Poly(ester-amide)s (PEAs) have a good melt processability and a less water absorption known as a serious drawback of polyamide. For these reasons, PEAs are attracting widespread interests in many researchers. Though much effort has been involved into PEAs, most of the existing studies have increased biodegradability by polymerizing aliphatic PEAs and to the best of our knowledge, only a few studies have been conducted on PEAs for engineering plastics containing aromatic residues. In this study, for the development of bioplastics having mechanical properties superior to PET, monomers for the polymerization of PEAs were selected and synthesized based on amino acids and dimethyl esters which are non-edible bio-based materials. In the initial stage of the research, polymerization was attempted by synthesizing monomers of terephthalamide structure in order to have better mechanical properties. Monomers of terephthalamide structure had a high melting point due to excellent packing between the benzene ring and hydrogen bonding due to the presence of adjacent amide bonds. By this reason, monomers were decomposed when the polymerization proceeded at the melt-process, which made monomers of terephthalamide structure not suitable as monomers for thermal bulk polymerization. To overcome this problem, the amide bond was introduced into the aliphatic diol to lower the melting point and dimethyl terephthalate having a low melting point was selected as the counterpart of polymerization that led to drastically lowering the melt-process temperature for thermal bulk polymerization. The thermal stability of every monomer and oligo-polymer synthesized by solution polymerization was evaluated. Four different diols were selected for thermal bulk polymerization based on the sufficient difference in their melting points and decomposition temperatures. In the same process as PET, thermal polymerization was successfully completed for all four diols and analyses were conducted by selecting the representative polymer synthesized with PSuP diol and DMT. Through FT-IR spectroscopy, it was confirmed that the polymer had both an ester bond and an amide bond. The model polymer having a weight average molecular weight of about 55,000 and a polydispersity index of 1.28 was polymerized. Thermal analysis showed that the glass transition temperature was nearly twice as high as that of PET, which enabled various fields to utilize PEAs in applications requiring much wider temperature range. Based on the results, the establishment of further experimental direction on how to change the internal carbon chain length of the diol will proceed.재생 가능한 자원을 기반으로 한 화학 물질 및 고분자 재료에 대한 관심이 높아지면서 바이오 기반 물질들에 대한 많은 연구들이 진행되고 있다. 전 세계 난분해성 바이오 플라스틱 생산량 1,2 위는 폴리에틸렌테레프탈레이트와 폴리아마이드이다. 폴리에틸렌테레프탈레이트는 낮은 물성과 유리전이온도를 가지는 명확한 단점을 보유하고 있다. 이러한 단점을 보완하기 위한 방법 중 하나로 폴리에스터와 폴리아마이드를 결합한 폴리에스터아마이드를 중합하고자 하는 연구들이 진행되고 있다. 현재까지, 지방족 단량체를 이용한 폴리에스터아마이드 중합에 관한 연구 외에 방향족 단량체를 포함시킨 중합에 관한 연구는 거의 진행되고 있지 않다. 폴리에틸렌테레프탈레이트 보다 우수한 물성의 바이오 플라스틱 개발을 위해 본 연구에서는 비식용 바이오 기반 물질인 아미노산과 다이메틸에스터를 기반으로, 폴리에스터아마이드 중합을 위한 단량체를 선정 및 합성하고 이의 합성을 진행하였다. 연구 진행 초기에는, 보다 우수한 물성을 보유하고자 테레프탈아마이드 형태의 단량체를 합성하여 중합을 시도하였다. 테레프탈아마이드 형태의 단량체는 벤젠 고리 사이의 우수한 적층성과 반복되는 아마이드 결합으로 인한 수소 결합으로 인해 높은 융점을 보유하여 용융 공정으로 중합을 진행 시 분해되는 현상이 발생하기 때문에 열 중합을 위한 단량체로 부적합하다고 판단하였다. 이를 개선하고자 아마이드 결합을 지방족 다이올에 도입시켜 융점을 낮추고, 중합 대응물로 융점이 낮은 다이메틸테레프탈레이트를 선정하여 열 중합을 위한 용융 공정 온도를 대폭 낮추었다. 중합에 사용되는 모든 단량체와 용액 중합을 통해 합성한 올리고폴리머의 열적 안정성을 평가하여 녹는점과 분해 온도가 충분한 차이를 나타내는 4 종류의 다이올을 선정하였고, 이를 이용한 열 중합을 진행하였다. 폴리에틸렌테레프탈레이트와 동일한 공정으로, 4 종류의 다이올 모두 열 중합을 성공적으로 진행 완료하였고 대표 중합체를 선정하여 여러 분석을 진행하였다. 적외선 분광법을 통해, 해당 고분자가 에스터 결합과 아마이드 결합 둘 모두를 보유함을 확인하였고, 젤 투과 크로마토그래피 분석을 통해 중량평균분자량이 약 55,000, 다분산지수는 1.28의 값을 가지는 고분자가 중합되었음을 확인하였다. 열 분석을 통해 유리전이온도가 폴리에틸렌테레프탈레이트에 비해 2 배 가까이 높음을 확인하여 훨씬 더 넓은 사용 온도 범위가 요구되는 분야에서의 활용 가능성을 확보하였다.Abstract i Contents v List of Tables and Figures viii 1. Introduction 1 2. Experiments 4 2.1. Materials 4 2.2. Synthesis of Monomers with Terephthalamide Structure 5 2.2.1. Ethanolamine-DMT-Ethanolamine (EDE) Trimer 5 2.2.2. Propanolamine-DMT-Propanolamine (PDP) Trimer 5 2.2.3. DMT-Cadaverine-DMT (DCD) X-mer 6 2.2.4. MCCB-Cadaverine-MCCB (MCM) Trimer 7 2.2.5. Tyramine-TCL-Tyramine (TTT) Trimer 9 2.2.6. Ethanol-Tyramine-TCL-Tyramine-Ethanol Pentamer 9 2.3. Synthesis of Aliphatic Diol Monomers Containing Amide Bonds 12 2.3.1. Dimethyl Malonate Based Diol (EME/PMP) 12 2.3.2. Dimethyl Succinate Based Diol (ESE/PSP) 13 2.3.3. Dimethyl Adipate Based Diol (EAE/PAP) 13 2.3.4. Dimethyl Suberate Based Diol (ESuE/PSuP) 14 2.4. Solution Polymerization of Poly(ester-amide)s 17 2.4.1. Polymerization with Terephthalamide Structure Monomers 17 2.4.1.1. EDE Trimer 17 2.4.1.2. MCM Trimer 17 2.4.1.3. TTT Trimer 19 2.4.2. Polymerization with Aliphatic Diol Monomers 19 2.5. Thermal Bulk Polymerization of Poly(ester-amide)s 20 2.5.1. Polymerization with Terephthalamide Structure Monomers 21 2.5.1.1. EDE/PDP Trimer, EG, and DMT Terpolymer 21 2.5.1.2. DCD X-mer Based Poly(ester-amide)s 24 2.5.1.3. Acetylation of TTT Trimer for Polymerization of Poly(ester-amide)s 26 2.5.2. Polymerization with Aliphatic Diol Monomers 26 2.5.2.1. Large Scale Polymerization for Preparation of Tensile Test Specimens 28 2.6. Characterization 29 2.7. Thermal Properties 30 2.8. Mechanical Properties 31 3. Results and Discussion 32 3.1. Synthesis of Monomers and Polymerization with Terephthalamide 32 3.2. Analyses of Causes of Failure in Thermal Bulk Polymerization and Establishment of New Experimental Direction 36 3.3. Synthesis of Tailor-made Diols Containing Amide Bonds and Thermal Properties of Diols 40 3.4. Polymerization of Poly(ester-amide)s with Tailor-made Diols 43 3.5. Establishment of Further Research Direction through Representative Compound Selection and Various Analyses Thereof 46 4. Conclusion 57 5. References 59Maste

A case of unexpected adjacent tooth extrusion after implant fixed prosthetic treatment, who had undergone mandibular resection and reconstruction due to ameloblastoma

Ameloblastoma is a benign odontogenic epithelial tumor with high recurrence rate and requires extensive resection of the surrounding tissue and reconstruction of defect site. Because of the anatomical limitation of the reconstruction site, prosthetic treatment with implants is the first recommendation. This is a case of prosthetic restoration of the reconstruction site with implant fixed prosthesis in patient who underwent mandibular resection and iliac bone reconstruction due to ameloblastoma. However 14 months after completion of implant prosthesis, adjacent natural tooth erupted unexpectedly, resulting in 1mm infra-occlusion occurred including posterior implant prosthesis and anterior natural teeth. In adults, implant infra-occlusion may occur due to residual growth after placement of the maxillary anterior implant. But this case, hypo-occlusion of molar implant and open bite of anterior natural teeth is occurred due to extrusion of adjacent tooth, is rare. Thus we report the treatment process including orthodontic treatment with intrusion of the posterior tooth, and investigate the causes of sudden, unexpected tooth extrusion.ope

Atomic Layer Deposition of Ni Thin Films and Application to Area-Selective Deposition

Ni thin films were deposited by atomic layer deposition (ALD) using bis(dimethylamino-2-methyl-2-butoxo)nickel [Ni(dmamb)(2)] as a precursor and NH3 gas as a reactant. The growth characteristics and film properties of ALD Ni were investigated. Low-resistivity films were deposited on Si and SiO2 substrates, producing high-purity Ni films with a small amount of oxygen and negligible amounts of nitrogen and carbon. Additionally, ALD Ni showed excellent conformality in nanoscale via holes. Utilizing this conformality, Ni/Si core/shell nanowires with uniform diameters were fabricated. By combining ALD Ni with octadecyltrichlorosilane (OTS) self-assembled monolayer as a blocking layer, area-selective ALD was conducted for selective deposition of Ni films. When performed on the prepatterned OTS substrate, the Ni films were selectively coated only on OTS-free regions, building up Ni line patterns with 3 mu m width. Electrical measurement results showed that all of the Ni lines were electrically isolated, also indicating the selective Ni deposition. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3504196] All rights reserved.ope

Importance of immediate surgical intervention and antifungal treatment for rhinocerebral mucormycosis: a case report

Rhinocerebral mucormycosis (RCM) is an opportunistic, potentially life-threatening fungal disease. This infective disease invades not only the facial sinuses, but also the maxilla, zygoma, and rhino-cerebral structures with a massive destruction of the facial skeletons and soft tissue. This disease progresses within various underlying diseases, such as diabetes mellitus, hematologic malignancy, renal failure, and systemic immunodepression. The relationship between mucormycosis and these underlying conditions have been discussed extensively in the literature. The authors studied 6 cases of RCM diagnosed by a tissue biopsy and treated at the department of oral and maxillofacial surgery, from 1997 to 2012. Patients were treated with several kinds of surgical interventions and antifungal agents, and their clinical & radiological signs, underlying conditions, surgical methods, and outcomes were analyzed.ope

Low-grade osteosarcoma arising from cemento-ossifying fibroma: a case report

Cemento-ossifying fibromas are benign tumors, and, although cases of an aggressive type have been reported, no cases of cemento-ossifying fibroma transforming into osteosarcoma have been documented previously. Low-grade osteosarcoma is a rare type of primary bone tumor, representing 1%-2% of all osteosarcomas. A 45-year-old female patient was diagnosed with cemento-ossifying fibroma, treated with mass excision several times over a period of two years and eight months, and followed up. After biopsy gathered because of signs of recurrence, she was diagnosed with low-grade osteosarcoma. The patient underwent wide excision, segmental mandibulectomy, and reconstruction with fibula free flap. The aim of this report is to raise awareness of the possibility that cemento-ossifying fibroma can transform into osteosarcoma and of the consequent necessity for careful diagnosis and treatment planning.ope

Development of Unsteady Preconditioned Multi-Phase Roem and Ausmpw+ Schemes

본 논문은 2015년도 미래창조과학부의 재원으로 NSL사업(NRF-2014M1A3A3A02034856)과 민ㆍ군협력 기술사업(Civil-Military Technology Cooperation Program)의 지원을 받아 작성되었습니다.OAIID:RECH_ACHV_DSTSH_NO:420160000004648010RECH_ACHV_FG:RR00200003ADJUST_YN:EMP_ID:A001138CITE_RATE:FILENAME:비정상_예조건화_기법을_적용한_다상유동_RoeMAUSMPW+_수치기법··.pdfDEPT_NM:기계항공공학부EMAIL:[email protected]_YN:FILEURL:https://srnd.snu.ac.kr/eXrepEIR/fws/file/696b8222-7074-43e7-8294-9499eb9c0b74/linkCONFIRM:

Reduction of superior-lateral intact mandibular condyle dislocation with bone traction hook

Lateral and superior-lateral dislocations of the intact condyle are a rare complication, following traumatic insult to the mandible. We report an unusual case of a 54-year-old male patient who experienced both types of dislocations of the intact condyles with symphysis fracture following a road-traffic accident. Under general anesthesia, conventional manipulation was unsuccessful in relocating the condyles into the glenoid fossa. After applying a percutaneous traction force, using a bone traction hook placed at the sigmoid notch, the displaced intact mandibular condyles were repositioned, and the symphyseal fracture was finally reduced and fixed. The mouth opening was within normal limits, and favorable occlusion was confirmed one month postoperatively. To our knowledge, this is the first case of dislocation of both intact condyles--associated with symphysis fracture--being reduced with bone traction hook.ope

Bisphosphonate 복용환자에서 임플란트를 식립하는 것이 정당한가?

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Considerations and Protocols in Virtual Surgical Planning of Reconstructive Surgery for More Accurate and Esthetic Neomandible with Deep Circumflex Iliac Artery Free Flap

Purpose: The reconstruction of mandibular defects poses many difficulties due to the unique, complex shape of the mandible and the temporomandibular joints. With development of microvascular anastomosis, free tissue transplantation techniques, such as deep circumflex iliac artery (DCIA) flap and fibular free flap (FFF), were developed. The DCIA offers good quality and quantity of bone tissue for mandibular segmental defect and implant for dental rehabilitation. Virtual surgical planning (VSP) and stereolithography-guided osteotomy are currently successfully applied in three-dimensional mandibular reconstruction, but most use FFF. There are only a few articles on reconstruction with the DCIA that assess the postoperative results. Methods: Three patients admitted during a five month period (April of 2013 to August of 2013) underwent resection of mandible and DCIA musculo-osseous reconstruction using a VSP and stereolithographic modeling and assessment of outcomes included technical accuracy, esthetic contour, and functional outcomes. Results: This technique yielded iliac bone segment with excellent apposition and duplication of the preoperative plan. Flap survival was 100 percent and all patients maintained preoperative occlusion and contour. Conclusion: Based on our experience, we offer considerations and logically consistent protocols by classification of mandibular defects, and demonstrate the benefits in VSP and stereolithographic modeling of mandibular reconstructive surgery with DCIA flap.ope