Abstract

Self-healing polymers can regain mechanical performance following damage, offering increased material durability and sustainability. This thesis establishes structure/property/processing relationships for a 3D printable extrinsically self-healing polymer based on a UV polymerizable thermosetting resin system blended with a low temperature thermoplastic healing agent. This work serves as the first example of a vat polymerization 3D printed soft, low Tg low-melt thermoplastic extrinsically self-healing polymer blend. This development enables high resolution fabrication of complex geometries with self-healing functionality. This strategy of imbuing self-healing properties onto vat polymerization resins will enable functionality in many application spaces including aerospace, biomedical, soft robotics, coatings, and military. Successful 3D printing of this type of material was found to have several requirements. The thermoplastic healing agent must first be miscible in the liquid resin system. This enables the light to be able to penetrate through the resin to initiate polymerization. This solubilizing of polymer unfortunately results in an increase of resin viscosity which results in difficulties in 3D printing, as lower resin viscosity are required for vat polymerization techniques. As the thermoset resin undergoes polymerization, the thermoplastic phase separates and subsequently crystallizes, resulting in a two-phase system. Upon heating above the thermoplastic’s melting temperature, it can flow into damaged regions; upon cooling, it recrystallizes to bond the fractured interfaces. Throughout this process, the thermoset phase preserves the overall geometric integrity of the structure. This work explores the intersection of materials chemistry and additive manufacturing by investigating how both the concentration and molecular weight of a thermoplastic healing agent influence 3D printability, as well as the resulting mechanical and self-healing properties of the printed material. In addition, the study explores how key 3D printing process parameters, specifically, print temperature and layer height, affect resin 3D printability and final material performance. This work lays the foundation for uncovering a deeper understanding of polymer behavior, paving the way for the design of highly functional, self-healing printed materials for a wide array of advanced applications.

Library of Congress Subject Headings

Polymers--Mechanical properties; Thermoplastics; Three-dimensional printing; Self-healing materials

Publication Date

2025

Document Type

Dissertation

Student Type

Graduate

Degree Name

Engineering (Ph.D.)

Department, Program, or Center

Engineering

College

Kate Gleason College of Engineering

Advisor

Christopher L. Lewis

Campus

RIT – Main Campus

Plan Codes

ENGR-PHD

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