Date of Completion

8-3-2020

Embargo Period

7-31-2022

Keywords

flame retardant, nanocoating, coassembly, montmorillonite, laponite, α-zirconium phosphate, halogen free, microscale combustion calorimetry

Major Advisor

Dr. Luyi Sun

Associate Advisor

Dr. Montgomery Shaw

Associate Advisor

Dr. Richard Parnas

Field of Study

Materials Science

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Fires account for approximately 3100 deaths and $10 billion in property damage annually in the US. Growing consumption of polymeric materials increases the potential damage a fire could cause. Halogenated chemicals have dominated as the primary means of flame retarding (FR) polymeric materials since the 1960s. However, regulation has required they be phased out of use, directing research towards halogen-free FR solutions. One emerging technology is nanocoatings. Nanocoatings are currently processed using direct mixing, in situ polymerization, and layer-by-layer deposition in attempts to achieve well-organized and highly dispersed nanosheets. These processing methods are limited by efficiency and scalability. Recently a method to fabricate nanocoatings through a one-step coassembly has been developed and shown to impart FR.

In this dissertation, we explore the mechanism of FR imparted by nanocoatings, synthesized using a one-step coassembly, and the effective contributions of the polymer binder and nanosheet have on FR properties. A series of nanocoatings with binders of polyvinyl alcohol (PVA), polyvinyl pyrrolidone, and poly ethylenimine (PEI) paired with montmorillonite (MMT) clay was applied to PET films, cotton fabrics, and open-cell polyurethane (PU) foams. The second series of nanocoatings varying nanosheets (MMT, laponite, and α-zirconia phosphate) were also applied to PET, cotton, and PU. PET was the most responsive substrate, and PVA/MMT nanocoating showed the most improvement in FR while cotton and PU responded best to PEI/MMT.

Several substrates were used to explore further and optimize FR nanocoatings. The char templating and oxidative resistance imparted by highly ordered nanocoating displayed extraordinary FR properties in increasing FR of 1.5 mm PBT sheets. Coating of exfoliated nanosheets imparted self-extinguishing properties onto semi-finished leather, highlighting their mechanism of oxidative resistance. PVA/MMT showed exceptional performance in treating cardboard, were a critical step in its combustion is the oxidation of its char. PVA/MMT coatings were minimally effective in improving FR of cotton fabrics, which need the addition of a functional polymer and char promoting agent to achieve self-extinguishing properties. This research advances the understanding of FR nanocoatings and their interactions with varied substrates.

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