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Author ORCID Identifier

https://orcid.org/0000-0003-1918-288X

AccessType

Open Access Dissertation

Document Type

dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Polymer Science and Engineering

Year Degree Awarded

2021

Month Degree Awarded

May

First Advisor

Prof. Alan Lesser

Subject Categories

Polymer and Organic Materials

Abstract

This dissertation focuses on engineering polymeric formulations using strategically selected additives or novel processes to achieve advanced material properties. The first chapter reviews the state-of-the-art impact modification and discusses micro-mechanics associated with soft particle toughening of polymeric materials. We present an analytical solution to elucidate the effect of concentration of rubbery domains on matrix yielding and energy absorption. Soft particle toughening relies on particle size, interparticle spacing, and concentration of rubbery phase. The second chapter demonstrates developing impact modified stereolithography (SLA) resins for the superior energy absorption of the SLA printed thermosets. SLA resins are engineered using additives that remain miscible in the uncured resin but undergo RIPS to generate rubbery domains after photopolymerization. SLA resins containing 15% of the identified impact modifier generates rubbery domains of appropriate size (57 nm) and inter-particle spacing (33 nm) to provide the most significant, order of magnitude, improvement in the impact properties irrespective of the print layer orientation and print layer thickness. The third chapter describes new strategies to obtain non-spherical rubbery domains for the next-generation impact modification. Firstly, blending of two different block copolymers with polypropylene is investigated to achieve non-spherical domains. Alternatively, elastomeric adducts are prepared via reactive mixing to realize non-spherical rubbery domains for polyoxymethylene. Impact properties of engineered polypropylene formulations show a strong dependence on particle size and shape under quasi-static room temperature as well as high strain, low temperatures (extreme conditions). The fourth chapter describes multifunctional organophosphorus additives for high Tg epoxy networks which achieve both enhanced mechanical and flame-retardant properties. These molecular additives remain miscible in the cured epoxy networks and participate in the mechanisms of fortification and flame inhibition. Herein, a systematic investigation of the effect of dimethyl methyl phosphonate (DMMP) on the mechanical and heat release properties of both conventional and inherently low flammability epoxy resins is presented. The integration of DMMP into epoxy networks produces materials with outstanding flame retardance and increased stiffness.

DOI

https://doi.org/10.7275/22271193.0

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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