Most
current flame-retardant nanocoatings for flexible polyurethane
foam (PUF) consist of passive barriers, such as clay, graphene oxide,
or metal hydroxide. In an effort to develop a polymeric and environmentally
benign nanocoating for PUF, positively charged chitosan (CH) and anionic
sodium hexametaphosphate (PSP) were deposited using layer-by-layer
(LbL) assembly. Only six bilayers of CH/PSP film can withstand flame
penetration during exposure to a butane torch (∼1400 °C)
for 10 s and stop flame spread on the foam. Additionally, cone calorimetry
reveals that the fire growth rate, peak heat release rate, and maximum
average rate of heat emission are reduced by 55, 43, and 38%, respectively,
compared with uncoated foam. This multilayer thin film quickly dehydrates
to form an intumescent charred exoskeleton on the surface of the open-celled
structure of polyurethane, inhibiting heat transfer and completely
eliminating melt dripping. This entirely polymeric nanocoating provides
a safe and effective alternative for reducing the fire hazard of polyurethane
foam that is widely used for cushioning and insulation.
Polyurethane
foam (PUF) is a highly flammable material typically
used for cushioning in furniture and automobiles. A polyelectrolyte
complex coating containing polyethylenimine, ammonium polyphosphate,
and halloysite clay was applied to PUF using a two-step deposition
process in an attempt to reduce its flammability. Electron microscopy
confirms that this conformal thin film preserves the porous morphology
of the foam and adds 20% to the foam’s weight. Directly exposing
coated foam to a butane torch flame yields a 73% residue after burning
while keeping the internal structure of the foam intact. Cone calorimetry
reveals a 52.5% reduction in the peak heat release rate (pkHRR) of
the clay-based coating compared to that of the uncoated foam. This
significant reduction in pkHRR and preservation of the porous structure
of the foam highlights the utility of this easy-to-deposit, environmentally
benign treatment to reduce the foam’s flammability.
Creating
multifunctional textiles using chemicals from renewable
sources is challenging. In an effort to develop a sustainable and
efficient multifunctional cotton treatment, a lignin-based multilayer
nanocoating comprising magnesium lignosulfonate, chitosan, and monoammonium
phosphate (MAP) was deposited using layer-by-layer assembly. A five
bilayer coating adds 15.5 wt % to cotton and imparts fire extinguishing
behavior and excellent UV and antimicrobial protection to the fabric.
Just a two bilayer coating imparts sufficient self-extinguishing behavior
to pass the standard vertical flame test. The combined influence of
lignin as a char-forming and UV-protective macromolecule, chitosan
as a char-forming biopolymer, and MAP acting as an antimicrobial agent
(and a blowing agent and an acid source in an intumescent flame retardant
system) results in a very powerful multifunctional textile treatment
with very few layers of deposition.
Bioactive core–shell nanoparticles (CSNPs) offer the unique ability for protein/enzyme functionality in non-native environments. For many decades, researchers have sought to develop synthetic materials which mimic the efficiency and catalytic power of bioactive macromolecules such as enzymes and proteins. This research studies a self-assembly method in which functionalized, polymer-core/protein-shell nanoparticles are prepared in mild conditions. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques were utilized to analyze the size and distribution of the CSNPs. The methods outlined in this research demonstrate a mild, green chemistry synthesis route for CSNPs which are highly tunable and allow for enzyme/protein functionality in non-native conditions.
Mixed solvent synthesized polydopamine is used in a multilayer nanocoating for protecting foam from fire. The use of LbL technology significantly reduces the processing time often observed with traditional methods polymerized from buffer.
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