무기 충전제 개질 및 압출 스크류 설계를 통한 고분자–무기 복합소재 물성 극대화 = Maximizing the properties of polymer–inorganic composites via inorganic filler modification and extrusion screw design

다국어 초록 (Multilingual Abstract)

The compatibility between two immiscible polymers in a blend is a critical factor in maximizing their overall properties. In this study, the effects of modified kaolin on the compatibility, molecular weight, molecular weight distribution, and various properties of poly(lactic acid) (PLA)/poly(vinyl butyral) (PVB) blends were systematically investigated. Kaolin was modified using different 3 M acids—hydrochloric acid, nitric acid, and sulfuric acid—under stirring at 75 ℃ for 4 h, followed by calcination at 550 ℃ for 2 h. The modified kaolin was then incorporated into PLA/PVB (8:2) blends at 5 phr and processed using a twin–screw extruder to prepare the composites. The incorporation of modified kaolin as a compatibilizer mitigated the inherent immiscibility between the two polymers and enhanced both mechanical and thermal properties. In particular, kaolin treated with HNO3 exhibited the most significant compatibilization effect, markedly improving tensile strength, Young’s modulus, elongation at break, and toughness. In contrast, the kaolin treated with H2SO4 showed reduced improvements due to chain scission induced by the strong acid and the presence of residual acid. Rheological characterization using a rheometer further revealed that the functionalized kaolin induced notable changes in the melt behavior of the blends. A comprehensive set of characterization techniques—including scanning electron microscopy (SEM), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, rheometry, and melt flow index (MFI)—was employed to analyze the structural, molecular, thermal, mechanical, and rheological characteristics of the composites. The structural modifications of the kaolin induced during the treatment process strengthened the interactions within the PLA/PVB blends, which was closely correlated with changes in molecular weight and improvements in material properties. Overall, this study elucidates how structural transformations of kaolin achieved through acid treatment and calcination enhance the compatibility of PLA/PVB blends, thereby offering a sustainable composite design strategy that bridges the gap between biodegradability and performance while broadening their potential applications.
In this study, the effects of controlling the dispersion and distribution of inorganic fillers within a polymer matrix through modifications in screw design were investigated. Polyamide 66, a widely used engineering plastic in industry, was employed as the polymer matrix, while silica, known for its good compatibility, was used as the inorganic filler. The screw design parameters examined in this work included the position of the neutral kneading element within the kneading zone, as well as the location and number of kneading zones within the screw. Prior to experimentation, the Ludovic simulation software was utilized to predict flow behavior and dispersion characteristics under various processing conditions. Specific Mechanical Energy (SME), residence time, viscosity, and cumulated strain were evaluated through the simulation. For the actual experiments, scanning electron microscopy (SEM) was used to analyze the morphology in order to assess the dispersion and distribution of the filler within the polymer matrix. The effects of the observed dispersion and distribution on mechanical and thermal properties were further examined using a universal testing machine (UTM), Izod impact testing, and differential scanning calorimetry (DSC). When the position of the neutral kneading element within the kneading zone was varied, dispersion and distribution improved as the neutral kneading element was placed closer to the reverse conveying element. In the investigation of the location and number of kneading zones within the screw, a greater number of kneading zones resulted in enhanced dispersion and distribution. Furthermore, the presence of a kneading zone near the hopper or the availability of sufficient conveying sections tended to improve distribution characteristics. Improved dispersion and distribution generally led to enhanced mechanical and thermal properties. This study provides insights into screw design strategies for achieving optimal material properties by controlling filler dispersibility in twin–screw extrusion processes. The findings can serve as foundational data for research on nano-filler dispersion and may be applied to process design and process prediction in polymer compounding.

목차 (Table of Contents)

• 1장. 연구 배경 및 목적 1
• 1. 연구 배경 1
• 2. 연구 목적 8
• 2장. 산 처리 및 소성을 통해 개질된 kaolin을 첨가한 Poly(lactic acid) (PLA)/Poly(vinyl butyral) (PVB) 복합재 10
• 1. 서론 10
• 2. 실험 14
• 3. 결과 및 고찰 24
• 4. 결론 52
• 3장. Polyamide 66 (PA66)/silica 복합재에서 충전제의 분산 및 분배를 제어하기 위한 스크류 요소 구성 최적화: 시뮬레이션–실험 통합 연구 54
• 1. 서론 54
• 2. 실험 57
• 3. 결과 및 고찰 67
• 4. 결론 106
• 결론 109
• References 112
• Abstract 120