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Chemical structural regulation of polyurethanes toward green materials

Title
Chemical structural regulation of polyurethanes toward green materials
Author
이주형
Alternative Author(s)
이주형
Advisor(s)
김성훈
Issue Date
2021. 8
Publisher
한양대학교
Degree
Doctor
Abstract
본 연구에서는 신규 폴리우레탄소재를 이용한 기능성 소재 개발 및 응용을 주제로, 식물성 오일 기반 다관능성을 폴리올을 이용한 고성능 형상 기억 엘라스토머, 상변화물질, 폴리우레탄 폼 등의 개발 및 응용에 관해 고찰하였다. 첫번째로, 고성능 형상기억 엘라스토머를 제조하기 위한 가교제로 사용하기 위하여 식물성 오일 기반 다관능성 폴리올을 합성하였다. 식물성 오일 가운데 피마자유 (Castor oil, CO)는 히드록실기와 C=C 이중결합을 내재하고 있어 다관능성 폴리올 합성의 출발 물질로 선정되었다. 피마자유에 mercaptoethanol과 1-thioglycerol을 thiol-ene 클릭 반응을 이용하여 grafting 하였다. 각각을 COM, COT로 명명하였으며, 제조된 폴리올의 화학 구조는 FT-IR과 1H-NMR 분석을 통해 확인하였으며, 하이드록실 수는 각각 270 mg KOH/g, 380 mg KOH/g로 피마자유의 160 mg KOH/g에 비해 점진적으로 증가하였음을 확인하였다. 바이오 폴리우레탄 (BPU)를 제조하기 하기 위하여 polycaprolactone diol을 소프트 세그먼트로 적용하고, hexamethylene diisocyanate 및 제조된 폴리올을 하드세그먼트로 하여 합성하였다. 제조된 BPU는 사용된 가교제의 종류에 따라 BPU-CO, BPU-COM, BPU-COT로 명명하였다. FT-IR 분석결과 폴리우레탄의 합성이 성공적으로 수행되었음을 확인하였으며, 가교제의 관능성이 증가할수록 분자 내 수소결합이 감소함을 확인하였다. XRD 및 DSC 분석결과로부터 가교밀도가 향상될수록 소프트 세그먼트와 하드 세그먼트 간의 상분리가 제한되어 결정화도가 감소하는 것을 확인하였다. TG 분석을 이용한 열안정성 시험 결과 BPU-COT가 가장 높은 온도에서 분해되어 열안정성이 높은 것으로 확인되었다. 기계적 물성 측정 결과 BPU-COT의 인장강도가 23MPa, 인장신도가 840%로 BPU-CO 대비 강도는 약 80% 향상되고 신도는 약 26% 감소하는 결과를 얻을 수 있었다. 더 높은 관능성을 갖는 가교제를 하드 세그먼트에 도입함으로써, BPU의 elastic recovery 특성이 향상되는 결과를 확인할 수 있었다. 두번째로, 폴리올 COM 및 COT을 이용하여 열에너지 저장을 위한 새로운 SSPCM을 성공적으로 제조하였다. PEG가 상변화 물질로 적용되었으며, CO, COM, 및 COT는 molecular framework로 적용되었다. FT-IR 분석결과, 폴리우레탄 구조가 형성된 것으로 확인되어 SSPCM의 합성이 성공적으로 수행되었음을 확인하였으며, XRD, POM 분석결과 고체-고체간 상변화가 이루어지는 것을 확인하였다. DSC 분석을 바탕으로 SSPCM의 열적 특성을 체계적으로 분석한 결과, 이소시아네이트 및 가교제의 종류가 상변화 특성에 매우 큰 영향을 미치는 것으로 파악되었다. HDI와 COT를 이용하여 제조된 SSPCM의 경우 126.5 J/g 의 가장 높은 상변화 엔탈피를 나타내었다. Thermal cycling 테스트 및 TG분석 결과 SSPCM의 내구성이 매우 우수한 것으로 확인되었다. 따라서, 초분기 폴리올을 이용한 SSPCM는 열에너지 저장 물질의 응용을 위한 매우 큰 잠재력을 가지고 있음을 확인하였다. 세번째로, CO, COM, COT 폴리올 블렌드를 제조하고 이를 이용한 PU 폼을 제조하였다. PU 폼의 구조는 FT-IR 분석을 통해 확인하였으며, 폼 셀 구조 형을 SEM 분석을 통해 관찰한 결과, 다관능성 폴리올의 함량이 증가할수록 밀도 높은 폼이 형성되는 것을 확인하였다. CO와 COM, COT의 혼합 비율이 50%일 때 까지는 PU 폼의 압축 강도가 50, 75%씩 상승하였다. 본 연구결과로부터, 다관능성 폴리올을 이용하여 압축강도가 향상된 PU 폼의 제조가 가능함을 확인하였다. 네번째로, 식물성 오일 기반 초분기 폴리올을 새로운 합성 루트를 이용하여 합성하였다. 식물성 오일 가운데 불포화 결합의 수가 가장 많은 것으로 알려진 포도씨유를 출발 물질로 선정하여, i) 에폭시화, ii) propargylation, iii) thiol-yne 클릭 반응을 통하여 초분기 폴리올을 제조하였다. FT-IR 및 1H-NMR 분석을 통하여 신규 폴리올의 합성이 성공적으로 이루어졌음을 확인하였으며, 하이드록실 수 분석 결과 612 mg KOH/g로 현재까지 보고된 식물성 오일 기반 폴리올 가운데 가장 높은 관능성을 갖는 것으로 확인되었다. 합성된 초분기 폴리올을 이용하여 PCL-diol과 MDI의 반응으로 생성된 PU 프리폴리머를 사슬 연장하였다. 이 PU의 기계적 물성은 분석한 결과, 인장강도 27MPa, 인장신도 2315%로, 1, 4 butanediol을 이용하여 제조된 Linear PU 대비 인장강도 및 신도 모두 크게 증가하는 결과를 얻을 수 있었다. |The main theme of this research is the development and application of novel polyurethane (PU) materials. PU is the most widely used polymer for various applications, such as coatings, adhesives, sealants, foams, composites, and energy materials. As the contents, this research was conducted on the PU based applications such as shape memory polyurethane (SMPU), phase change material (PCM), PU foam (PUF). First, vegetable oil-based multifunctional polyols were synthesized for use as high performance crosslinker for SMPU. Among the vegetable oils, castor oil (CO) was employed as a starting material for multifunctional polyols due to its hydroxyl groups and C=C double bonds in nature. The novel polyols with gradually increased hydroxyl value were synthesized by grafting 2-mercaptoethanol or α-thioglycerol (modified polyols hereafter denoted as denoted as COM or COT, respectively) into CO via a thiol-ene click reaction. The success of the grafting reactions for the as-prepared polyols was confirmed by FT-IR and 1H-NMR analyses. The hydroxyl value of CO gradually increased from 160 mg KOH/g to 270 mg KOH/g and 380 mg KOH/g for the COM and COT, respectively. Bio-PU (BPU) were prepared by synthesis of polycaprolactone-diol (PCL-diol), hexamethylene diisocyanate (HDI) and the as-prepared CO-based multifunctional polyols as a crosslinking agent. For comparison, SMPU using CO as a crosslinking agent was also prepared. The prepared BPUs were designated as BPU-CO, BPU-COM, and BPU-COT according to the crosslinker used. The chemical structural properties of the prepared BPUs were analyzed by Fourier transform infrared (FT-IR) spectroscopy. Based on X-ray diffraction (XRD) and differential scanning calorimetry (DSC) results, it was confirmed that the phase separation between the soft and hard segments was limited because of the increase in the crosslinking density, results in decrease in crystallinity. Based on mechanical property measurements, the tensile strength of BPU-COT was 23 MPa and the tensile elongation was 840%. Compared to BPU-CO, the strength was improved by ~80%, and the elongation was decreased by about 26%. By introducing a crosslinking agent having a higher functionality into the hard segment, improvements of the mechanical and elastic recovery property of BPU were confirmed. Second, polymeric solid-solid phase change materials were developed using prepared CO-based multifunctional polyols. Polyethylene glycol (PEG) was used as the phase change material in the SSPCMs, while CO, COM, and COT served as molecular framework. Two types of diisocyanate, HDI and 4,4'-diphenylmethane diisocyanate (MDI) were used for the synthesis. FT-IR analysis results indicated PU structures that confirmed the successful synthesis of the SSPCMs and XRD and POM analyses results indicated solid–solid phase transition. The thermal transition properties of the SSPCMs were systematically analyzed using DSC. The results suggested that the isocyanate and crosslinker type had a significant influence on the phase transition properties. The SSPCM prepared using HDI and COT samples exhibited the highest phase transition enthalpy at 126.5 J/g. The results of the thermal cycling test and TG analysis demonstrated outstanding durability of SSPCMs. Thus, the novel SSPCM based on hyper-branched polyols has great potential to be successfully applied in thermal energy storage materials. Third, polyol blends were prepared by mixing CO with COM and COT, and their characteristics were analyzed. The PU foams derived from CO-based polyol blends were synthesized via a free-rising method. The property changes of the PU foams resulting from the increasing functionality of the polyol blends were thoroughly examined. PU foams were fabricated using polyol blends, and their structures were determined via FT-IR analysis. It was confirmed that the PU foams structure was affected by the composition and ratio of the blended polyols. Morphological analysis of the PU foams revealed that an optimal proportion of CO in the polyol blends led to the formation of a dense structure. As the blending ratios of COM and COT increased up to 50%, the compressive strengths of the PU foams increased by 50 and 75%, respectively. Overall, we believe that bio-based PU foams made of CO-based multifunctional polyol may find a wide range of applications that require high compressive strength. Fourth, a novel bio-based hyperbranched polyol with high functionality was prepared from grapeseed oil (GSO) through the following sequential reaction; i) epoxidation, ii) propargylation and iii) thiol-yne click reaction. The structural analysis were confirmed that the GSO-based hyperbranched polyol was synthesized successfully, and the hydroxyl value of synthesized hyperbranched polyol was 612 mg KOH/g which are closed to commercial hyperbranched polyol. BPU films were prepared by employing the hyperbranched polyol as a crosslinker. The synthesis of PUs using 2 step prepolymer polymerization. The prepolymer was obtained by end-capping of PCL-diol with MDI, followed by chain-extended with 1,4-BD, prepared hyperbranched polyol, and their mixture to verify the effect of hyperbranched structure. The successful synthesis of the hyperbranched PUEs were confirmed by FT-IR analysis. The crystallinity of prepared hyperbranched PUEs was decreased due to crosslinking network in BPUs disturbing formation of crystalline structure. Based on mechanical property analysis, the tensile strength of BPU 3 was 27 MPa and the tensile elongation was 2315%. By introducing a crosslinker with a hyperbranched structure, the tensile strength of the PUEs as well as the tensile elongation were significantly increased.
URI
http://hanyang.dcollection.net/common/orgView/200000500652https://repository.hanyang.ac.kr/handle/20.500.11754/164103
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GRADUATE SCHOOL[S](대학원) > ORGANIC AND NANO ENGINEERING(유기나노공학과) > Theses (Ph.D.)
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