Development and Characterization of Various Phosphorus-Based Reactive Flame Retardants for Epoxy Resin Systems Used as a Matrix for High-Performance Fiber Reinforced Composites

Date of Award

5-1-2025

Degree Name

Ph.D. in Materials Engineering

Department

Department of Materials Engineering

Advisor/Chair

Donald Klosterman

Abstract

This dissertation investigates the development and application of non-halogenated, phosphorus-based reactive flame retardants in epoxy resin systems, focusing on optimizing the balance between fire resistance, mechanical properties, ease of processing, and cost-efficiency. Traditional halogenated retardants, while effective, pose significant environmental risks, necessitating the exploration of safer alternatives. Chapter 1 discusses the challenges of enhancing fire resistance in epoxy resins without relying on halogenated compounds. It emphasizes the need for solutions that integrate seamlessly with epoxy matrices, maintaining or enhancing mechanical performance cost-effectively. This chapter underscores the significance of this research in modern material science, highlighting the need for materials that can resist rapid combustion and meet stringent fire safety standards while being economical and easy to process. Chapter 2 presents a literature review showing the state-of-the-art in reactive phosphorus-based retardants and their ability to improve fire resistance through multiple mechanisms. It also identifies existing gaps in achieving an optimal balance with mechanical properties. Chapter 3 details the testing of FR5, an amine-functionalized phosphorus hydrazide, noting its effectiveness in improving char formation and smoke reduction but its limited impact on peak heat release rates. This result indicates the need for further development or combinations with other retardant chemistries to enhance effectiveness. Chapter 4 explores the use of P-DGEBA, a phosphorus-modified epoxy monomer, in carbon fiber composites, revealing its ability to enhance the glass transition temperature and reduce heat release. However, further studies are needed to fully understand its impact on composite properties and processing. Chapter 5 investigates the effects of commercially available phosphorus-based flame retardants like Fyrol PMP and DOPO on blends of DGEBA epoxy (EP) with cyanate ester, including several cyanate ester monomers such as LECy and LVT-100. This work demonstrates significant advances in thermal stability and processing capabilities, which suggests potential for reduced manufacturing costs while considering the trade-offs in mechanical properties. Chapter 6 focuses on the transformative impact of incorporating PMP in LVT-100/EP blends, highlighting its unexpected role in accelerating curing processes and enhancing manufacturability without compromising material integrity. Chapter 7 delves into the dual-stage curing kinetics of resin blends containing PMP, providing insights into the processing dynamics of LVT-100/EP/PMP blends. It emphasizes the efficiency of PMP in reducing gelation times and optimizing cure cycles, significantly aiding high-quality composite panel manufacturing. Differential Scanning Calorimetry and parallel plate rheology were used to explore the catalytic behavior, which provided key information needed to modify the cure cycle of PMP-containing composites so that acceptable fiber volume fraction could be achieved. This chapter stresses the importance of precise control over processing conditions to maximize the benefits of PMP, balancing curing efficiency with processability for optimal composite quality. In conclusion, this research demonstrates the use of phosphorus-based flame retardants for achieving an optimized balance between fire safety, mechanical integrity, and processing efficiency in epoxy and epoxy/cyanate resin systems. The findings advance the field by adding new knowledge to a material formulation space previously unexplored, highlighting complex interactions between composition, processing, and the resulting balance of properties in both neat resin and carbon fiber reinforced samples. As such, this study provides a valuable resource for future innovations in safety-critical applications.

Keywords

Aerospace Materials, Chemical Engineering, Engineering, Materials Science

Rights Statement

Copyright 2025, author.

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