Date of Completion

7-31-2013

Embargo Period

7-31-2013

Keywords

Fire safety, flame retardant, stannate, hydroxystannate, synthesis, nano, solution processing, sustainability

Major Advisor

Dr. Puxain Gao

Associate Advisor

Dr. S. Pamir Alpay

Associate Advisor

Dr. George Rossetti Jr.

Field of Study

Materials Science and Engineering

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Statistically, accidental residential and vehicle fires cause ~3000 fatalities, and ~$10 billion in damages per year in the United States. To reduce the hazard, many flammable products are protected with bromated flame-retardants. However, studies have proven their use to pose major environmental and health hazards. A recent EPA mandate calls to phase out common formulations by 2014. To fill the void, incorporation of replacements is critical, however few offer such efficient and versatile protection. This dissertation intends to provide solutions through research and development of non-toxic zinc and calcium hydroxystannate (ZHS, CHS) nanoparticle based flame retardants for common textiles.

Using low-temperature solution synthesis methods, single crystalline ZHS micro- and nanocubes have been successfully grown on pure tin substrates. Cube morphology was controlled by altering reaction time and chemical reagents. Their thermal decomposition process was investigated using differential scanning calorimetry, thermal gravitational analysis and electron microscopy. An endothermic peak near ~540K is attributed decomposition of ZHS into ZnSnO3.

Furthermore, successful incorporation of hydroxystannate nanomaterial surface-coatings onto cotton, nylon and polyester textile fibers is achieved using a novel sustainable solution chemistry method. Alteration of the driving force/kinetics of nucleation and growth in these systems through control of precursor concentration, reaction time and temperature is used to tailor the coating particle morphology and mass loading. Associated fire-retardancy properties have been assessed and characterized by using standardized NFPA 705, ASTM D6413, and cone calorimetry tests. Hydroxystannate-coated nylon and polyester textiles demonstrate marginal, if any, performance increase, partially resulting from the scaffolding effect. However, hydroxystannate-coated cotton exhibits pronounced improvements in flame retardancy via physical mechanisms including morphology induced thermal and oxygen barrier properties, and thermally induced endothermic phase changes. As a result, the hydroxystannate nanomaterial systems display superior time-to-ignition and peak heat release rates (PHRRs) in comparison with the leading commercial flame retardant cotton. Furthermore, the strong correlation between burn-rates and PHRRs suggests that burn-rate analysis may provide a simplified method of estimating these values when compared to expensive cone calorimetry. This research advances the understanding of hydroxystannate flame retardant surface coatings.

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