Study on Photocurable Hybrid Materials for Dental and Membrane Applications Fabricated by Digital Light Processing 3D Printing

다국어 초록 (Multilingual Abstract)

This study investigated the development of photocurable hybrid resins for digital light processing （DLP）-based 3D printing and the fabrication of hierarchical separation membranes for oil–water separation. Urethane acrylate-based hybrid resins incorporating silane-functionalized barium-glass fillers were synthesized to enhance dimensional stability, mechanical performance, and radiopacity. The structural and physicochemical properties of the resins were examined via Fourier-transform infrared spectroscopy, gel permeation chromatography, rheological characterization, dispersion stability analysis, and standardized mechanical testing. An optimized ultraviolet （UV） exposure time of 2 s yielded the highest accuracy in layer formation, and the formulation containing 15 wt% barium glass exhibited the most favorable balance between dispersion stability, flexural and tensile properties, and radiopacity, where a 1 mm specimen corresponded to an aluminum-equivalent thickness of approximately 1.75 mm.
Based on the optimized resin formulation, hierarchical separation membranes were fabricated via DLP printing of polyurethane-based microstructured meshes, followed by nanoscale surface modification using silica nanoparticle/UV-curable polydimethylsiloxane （PDMS） coatings. Post-curing behavior was evaluated to establish appropriate crosslinking conditions. The results indicated that a UV exposure time of 5 min achieved effective network formation without inducing significant photodegradation. The resulting hierarchical surfaces exhibited a water contact angle of approximately 143°, stable resistance to ultrasonic agitation, and consistent separation performance under various pH conditions. Particularly, the membrane coated with 100 wt% silica/PDMS coating maintained separation efficiency for more than 30 operation cycles; moreover, the modulation of the pore size from 150 to 450 µm enabled the control of permeation flux and separation characteristics, with the 450 µm mesh achieving flux values of up to 70,000 L·m⁻²·h⁻¹ at an efficiency of approximately 95%.
These findings establish an integrated framework that links resin formulation, photopolymerization behavior, hierarchical surface engineering, and separation performance. The photocurable hybrid resins and DLP-printed hierarchical membranes developed in this study demonstrate significant potential for precision additive manufacturing and advanced oil–water separation technologies.

국문 초록 (Abstract)

본 연구에서는 디지털 광조형（Digital Light Processing, DLP） 3D 프린팅 공정에 적합한 광경화성 유무기 하이브리드 레진을 설계하고, 이를 기반으로 계층형 구조를 갖는 오일–물 분리용 멤브레인을 제작하였다. 우레탄 아크릴레이트 기반 올리고머에 실란 처리된 바륨 글라스 충진재를 도입하여 치수 안정성, 기계적 강도, 방사선 불투과성 향상을 목표로 하였으며, FT-IR, GPC, 점도·분산 안정성 분석, ISO·ASTM 규격에 따른 기계적 평가를 통해 조성–물성 관계를 체계적으로 규명하였다. 최적 UV 조사 시간은 2.0 s였으며, 15 wt% 바륨 글라스 조성은 분산성, 강도, 방사선 불투과성의 균형이 가장 우수하여 1.0 mm 시편 기준 약 1.75 mm Al-equivalent 수준의 불투과성을 확보하였다.
이 조성을 기반으로 DLP 프린팅된 폴리우레탄 격자（mesh）에 실리카 나노입자/UV-경화 PDMS 복합 코팅을 적용하여 마이크로–나노 계층 구조를 구현하였다. 후경화 조건 분석 결과, 5 min UV 조사에서 안정적 네트워크 형성이 확인되었으며, 제작된 표면은 약 143°의 높은 물 접촉각과 초음파·다양 pH 환경에서의 구조적 안정성을 나타냈다. 또한 기공 크기（150–450 µm） 변화에 따라 유량과 분리 효율을 조절할 수 있었으며, 450 µm 구조는 약 70,000 L·m⁻²·h⁻¹의 유량과 95% 수준의 효율을 유지하였다. 실리카 100 wt% 코팅 시 30회 이상의 연속 분리 사이클에서도 성능 저하가 관찰되지 않았다.
본 연구는 （1） 광경화성 하이브리드 레진의 조성 설계, （2） DLP 기반 정밀 적층 제조, （3） 계층형 표면 공정, （4） 유체 분리 특성 간의 상관성을 통합적으로 제시함으로써 기능성 3D 프린팅 소재 개발의 설계 지침을 마련하였다는 점에서 학술적·산업적 의의를 갖는다.

목차 (Table of Contents)

• Chapter 1. Introduction 1
• 1.1 Theoretical Background and Literature Review 1
• 1.1.1 Three-dimensional Printing 1
• 1.1.2 Three-dimensional Printing Materials 9
• 1.1.3 Ultraviolet-assisted 3D Printing 13
• 1.1.4 Photopolymerization 19
• 1.1.5 Urethane Acrylate 25
• 1.1.6 Nanocomposite Materials for 3D Printing 31
• Chapter 2. Mechanical Properties Improvement of 3D-Printed Aesthetic Dental Artificial Crowns Using UV-Curable Ceramic- Urethane Acrylate Nano-Composite Resins with Varying Filler Ratios 34
• 2.1 Introduction 34
• 2.1.1 Theoretical Background 34
• 2.2 Materials and Methods 37
• 2.2.1 Materials 37
• 2.2.2 Synthesis of Urethane Acrylate 40
• 2.2.3 Preparation of Hybrid Composite Resins 43
• 2.2.4 Evaluation of Dispersion Stability 47
• 2.2.5 Optimization of DLP Printing Conditions 49
• 2.2.6 Mechanical Property Evaluation 51
• 2.2.7 Radiopacity Evaluation 53
• 2.3 Results and Discussion 55
• 2.3.1 Characteristics of Urethane Acrylate Oligomer 55
• 2.3.2 Dimensional Accuracy under Different UV Exposure Times 58
• 2.3.3 Storage Stability Depending on Filler Content 63
• 2.3.4 Dispersion Stability of the Composite Resin 67
• 2.3.5 Mechanical Properties Depending on Filler Content 70
• 2.3.6 Radiopacity of the Hybrid Composite Resin 74
• 2.4 Conclusion 79
• 2.4.1 Conclusion· 79
• Chapter 3. Digital Light Processing Technique Aided 3D printing Hierarchical Super-wetting Mesh Coated with Hydrophobic SiO ₂ for highly efficient Oil-Water Separation 82
• 3.1 Introduction 82
• 3.1.1 Theoretical Background 82
• 3.2 Materials and Methods 85
• 3.2.1 Materials 85
• 3.2.2 Fabrication of Mesh Structures via DLP Printing 86
• 3.2.3 Synthesis of Superhydrophobic Silica （m-SiO₂） 87
• 3.2.4 Superhydrophobic Coating of PU Meshes 88
• 3.3 Results and Discussion 89
• 3.3.1 Fabrication of DLP-Printed Hierarchical Mesh 89
• 3.3.2 Effects of Post-Curing Conditions 92
• 3.3.3 Influence of Surface Structures on Superhydrophobicity 95
• 3.3.4 Effect of Silica Content on Durability and Surface Behavior 98
• 3.3.5 Separation Performance Depending on Pore Size 101
• 3.4 Conclusion 104
• 3.4.1 Conclusion 104
• Chapter 4. General Summary and Conclusion 106
• 4.1 Summary and Conclusion 106
• 4.1.1 Summary 106
• 4.1.2 Conclusion· 108
• References 110
• Acknowledgments 118