A variety of materials were used to fabricate nanocoatings using layer-by-layer
(LbL) assembly to reduce the flammability of cotton fabric. The most effective
brominated flame retardants have raised concerns related to their toxicity and
environmental impact, which has created a need for alternative flame retardant
chemistries and approaches. Polymer nanocomposites typically exhibit reduced mass
loss and heat release rates, along with anti-dripping behavior, all of which are believed
to be due to the formation of a barrier surface layer. Despite these benefits, the viscosity
and modulus of the final polymeric material is often altered, making industrial
processing difficult. These challenges inspired the use of LbL assembly to create densely
layered nanocomposites in an effort to produce more flame-retardant coatings.
Laponite and montmorillonite (MMT) clay were paired with branched
poly(ethylenimine) to create thin film assemblies that can be tailored by changing pH
and concentration of aqueous deposition mixtures. Both films can be grown linearly as a
function of layers deposited, and they contained at least 70 wt percent of clay. When applying
these films to cotton fabric, the individual fibers are uniformly coated and the fabric has significant char left after burning. MMT-coated fabric exhibits reduced total heat release,
suggesting a protective ceramic surface layer is created.
Small molecule, POSS-based LbL thin films were also successfully deposited on
cotton fabric. With less than 8 wt percent added to the total fabric weight, more than 12 wt percent
char remained after microscale combustion calorimetry. Furthermore, afterglow time
was reduced and the fabric weave structure and shape of the individual fibers were
highly preserved following vertical flame testing. A silica-like sheath was formed after
burning that protected the fibers.
Finally, the first intumescent LbL assembly was deposited on cotton fabric. SEM
images show significant bubble formation on fibers, coated with a 0.5 wt percent PAAm/1
wt percent PSP coating after burning. In several instances, a direct flame on the fabric was
extinguished. The peak HRR and THR of coated fabric has 30 percent and 65 percent reduction,
respectively, compared to the uncoated control fabric. These anti-flammable
nanocoatings provide a relatively environmentally-friendly alternative for protecting
fabrics, such as cotton, and lay the groundwork for rendering many other complex
substrates (e.g., foam) flame-retardant without altering their processing and desirable
mechanical behavior.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2011-05-9203 |
| Date | 2011 May 1900 |
| Creators | Li, Yu-Chin |
| Contributors | Grunlan, Jaime C. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | application/pdf |
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