불포화 폴리에스터의 MDI 첨가가 유리섬유직물 복합재료의 기계적 및 열적 특성에 미치는 영향

다국어 초록 (Multilingual Abstract)

In recent years, extensive research has been conducted to enhance the thermal stability and maximize the mechanical performance of unsaturated polyester resins (UPR), which are widely used in the composite industry. While UPRs possess excellent processability, they are characterized by relatively low thermal durability and limited interfacial bonding with glass fibers. To overcome these limitations, this study incorporated 4,4'-methylene diphenyl diisocyanate (MDI) at various weight fractions and comprehensively analyzed the resulting changes in the thermal, physical, and mechanical properties of glass fiber fabric composites. For the structural and thermal characterization of the modified resin, FT-IR, viscosity, DSC, and TGA analyses were performed. The physical properties of the composites were evaluated by measuring thickness, density, fiber volume fraction, and void content, while changes in the glass transition temperature and cross-link density were analyzed using DMA. Furthermore, mechanical performance was assessed by measuring tensile, flexural, and interlaminar shear strength (ILSS) using a UTM, and SEM was employed for cross-sectional analysis to observe void formation and morphological changes in the fracture surfaces. Additionally, accelerated thermal aging tests were conducted to compare mechanical properties before and after aging, thereby verifying long-term thermal durability. The results indicated that while the inherent thermal stability of the resin significantly improved with increasing MDI content, a slight deterioration in physical properties was observed at concentrations of 2.0wt.% or higher due to increased viscosity. However, mechanical evaluations confirmed a robust chemical modification effect that compensated for these physical drawbacks. In particular, the composite with 1.5wt.% MDI exhibited optimal values in terms of both and all mechanical indices. In conclusion, this study confirms that the addition of an appropriate amount of MDI induces the formation of urethane bonds within the UPR matrix, thereby significantly enhancing the overall physical properties and thermal durability of the resulting composites.

목차 (Table of Contents)

• 1. 서론 1
• 2. 이론적 배경 4
• 2.1 섬유강화 복합재료(FRP) 4
• 2.2 불포화 폴리에스터(Unsaturated Polyester Resin, UPR) 5
• 2.3 MDI(4,4'-methylene diphenyl diisocyanate) 7
• 2.4 압축 성형(Compression Molding) 9
• 2.5 연구 목표 10
• 3. 실험 및 방법 11
• 3.1 실험 재료 11
• 3.2 시편 제조 13
• 3.2.1 MDI 함량별 UPR 수지 제조 13
• 3.2.2 MDI 함량별 UPR/유리섬유 복합재료 제조 15
• 3.3 측정 17
• 3.3.1 FT-IR(Fourier transform infrared) 분석 17
• 3.3.2 점도(Viscosity) 분석 18
• 3.3.3 시차주사열량 분석(Differential Scanning Calorimeter; DSC) 19
• 3.3.4 열중량 분석 (Thermogravimetric Analyzers; TGA) 20
• 3.3.5 복합재료 물리적 물성 분석 21
• 3.3.6 복합재료 점탄성 분석 (Dynamic mechanical analyzer; DMA) 22
• 3.3.7 복합재료 기계적 물성 분석 23
• 3.3.8 전자주사현미경(Scanning Electron Microscope; SEM) 분석 24
• 3.3.9 복합재료의 내열성 분석 25
• 4. 결과 및 고찰 26
• 4.1 MDI 함량별 UPR 수지 분석 26
• 4.1.1 MDI 함량별 UPR 수지의 FT-IR 분석 26
• 4.1.2 MDI 함량별 UPR 수지의 점도 분석 30
• 4.1.3 MDI 함량별 UPR 수지의 DSC 분석 32
• 4.1.4 MDI 함량별 UPR 수지의 TGA 분석 34
• 4.2 MDI 함량별 복합재료의 물리적 물성 분석 36
• 4.2.1 MDI 함량별 복합재료의 두께 분석 36
• 4.2.2 MDI 함량별 복합재료의 밀도 분석 38
• 4.2.3 MDI 함량별 복합재료의 섬유부피분율(Vf) 분석 40
• 4.2.4 MDI 함량별 복합재료의 기공률(Vc) 분석 42
• 4.3 MDI 함량별 복합재료의 점탄성 분석 44
• 4.4 MDI 함량별 복합재료의 기계적 물성 분석 47
• 4.4.1 MDI 함량별 복합재료의 인장강도 분석 47
• 4.4.2 MDI 함량별 복합재료의 굴곡강도 분석 49
• 4.4.3 MDI 함량별 복합재료의 층간전단강도 분석 51
• 4.5 MDI 함량별 복합재료의 단면(SEM) 분석 53
• 4.6 열노화 처리에 따른 복합재료의 기계적 물성 분석 55
• 5. 결론 58
• 6. 참고문헌 60
• Abstract 67