Fire Resistant Adhesive from Chitosan.

Chitosan is one of the most abundant biopolymers on earth. It is used as a nontoxic alternative in a wide range of medicines, packaging, adhesives, and flame retardants. Chitosan is poorly soluble in neutral or alkaline solutions, but it dissolves in solutions of weak acids, such as acetic acid or citric acid, both of which occur naturally.

Nanobrick Wall Multilayer Thin Films with High Dielectric Breakdown Strength.

Current thermally conductive and electrically insulating insulation systems are struggling to meet the needs of modern electronics due to increasing heat generation and power densities. Little research has focused on creating insulation systems that excel at both dissipating heat and withstanding high voltages (i.e.

Synergistic Fire Resistance of Nanobrick Wall Coated 3D Printed Photopolymer Lattices.

Photopolymer additive manufacturing has become the subject of widespread interest in recent years due to its capacity to enable fabrication of difficult geometries that are impossible to build with traditional manufacturing methods. The flammability of photopolymer resin materials and the lattice structures enabled by 3D printing is a barrier to widespread adoption that has not yet been adequately addressed. Here, a water-based nanobrick wall coating is deposited on 3D printed parts with simple (i.

Polyelectrolyte Complex with Controllable Viscosity by Doping Cu Protects Nylon-Cotton Fabric against Fire.

Nylon-cotton (NC) blend fabrics are widely used in military and industrial applications, but their high flammability still remains a serious problem. In an effort to effectively and quickly impart flame retardancy to the NC fabric, it was treated by simply blade coating with a Cu-doped polyelectrolyte complex (CPEC) that consists of ammonium polyphosphate (APP), polyethylenimine (PEI), and copper sulfate. The viscosity of the CPEC can be adjusted by altering the content of CuSO, which controls the amount of extrinsic and intrinsic ion pairs.

Non-Isocyanate Polyurethane Bio-Foam with Inherent Heat and Fire Resistance.

Polyurethanes (PUs) are versatile and widespread, particularly as flexible and rigid foams. To avoid isocyanates and other toxic reagents required for synthesis, such as phosgene, alternative synthetic routes have been utilized to produce non-isocyanate polyurethanes (NIPUs). A thermally and flame-resistant rigid NIPU was produced from environmentally benign and bio-sourced ingredients, requiring no catalyst or solvents.

Biorenewable Polyelectrolyte Nanocoating for Flame-Retardant Cotton-Based Paper.

Cotton-based raw paper, made of 100% cellulose, is used to make humidity-sensing, cottonid for bio-architecture applications. Despite its renewability and excellent mechanical properties, it is inherently flammable. In an effort to reduce its flammability, thin films of fully renewable and environmentally benign polyelectrolytes, chitosan (CH) and phytic acid (PA), were deposited on raw paper via layer-by-layer (LbL) assembly.

Layer-by-Layer Deposition: A Promising Environmentally Benign Flame-Retardant Treatment for Cotton, Polyester, Polyamide and Blended Textiles.

A detailed review of recent developments of layer-by-layer (LbL) deposition as a promising approach to reduce flammability of the most widely used fibers (cotton, polyester, polyamide and their blends) is presented. LbL deposition is an emerging green technology, showing numerous advantages over current commercially available finishing processes due to the use of water as a solvent for a variety of active substances. For flame-retardant (FR) purposes, different ingredients are able to build oppositely charged layers at very low concentrations in water (e.

Efficient Heat Shielding of Steel with Multilayer Nanocomposite Thin Film.

In an effort to protect metal substrates from extreme heat, polymer-clay multilayer thin films are studied as expendable thermal barrier coatings. Nanocomposite films with a thickness ranging from 2 to 35 μm were deposited on steel plates and exposed to the flame from a butane torch. The 35 μm coating, composed of 14 deposited bilayers of tris(hydroxymethyl)aminomethane (THAM)-buffered polyethylenimine (PEI) and vermiculite clay (VMT), decreased the maximum temperature observed on the back side of a 0.

Clay-Filled Polyelectrolyte Complex Nanocoating for Flame-Retardant Polyurethane Foam.

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.

Environmentally-Benign Phytic Acid-Based Multilayer Coating for Flame Retardant Cotton.

Chemically bleached cotton fabric was treated with phytic acid (PA), chitosan (CH) and urea by means of layer-by-layer (LbL) deposition to impart flame retardant (FR) behavior using only benign and renewable molecules. Samples were treated with 8, 10, 12 and 15 bilayers (BL) of anionic PA and cationic CH, with urea mixed into the aqueous CH solution. Flammability was evaluated by measuring limiting oxygen index (LOI) and through vertical flame testing.

Super Gas Barrier of a Polyelectrolyte/Clay Coacervate Thin Film.

Transparent polymeric thin films with high oxygen barrier are important for extending the shelf life of food and protecting flexible organic electronic devices. Polyelectrolyte/clay multilayer nanocoatings are shown to exhibit super gas barrier performance, but the layer-by-layer assembly process requires numerous deposition steps. In an effort to more quickly fabricate this type of barrier, a polyelectrolyte/clay coacervate composed of branched polyethyleneimine (PEI), poly(acrylic acid) (PAA), and kaolinite (KAO) clay is prepared and deposited in a single step, followed by humidity and thermal post-treatments.

Environmentally Benign and Self-Extinguishing Multilayer Nanocoating for Protection of Flammable Foam.

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.

UV-protection from chitosan derivatized lignin multilayer thin film.

Lignin is one of the most abundant renewable materials on the earth. Despite possessing useful antioxidant and UV absorbing properties, its effective utilization in technology has been hampered by its relative insolubility and difficulty to process. In this work, a simple chemical derivatization process is utilized which yields water-soluble lignin possessing anionic carboxylate groups.

Mica-Based Multilayer Nanocoating as a Highly Effective Flame Retardant and Smoke Suppressant.

Highly flammable polyurethane foam (PUF) remains a key risk factor associated with bedding and upholstered furniture, contributing to the yearly destruction of property and loss of lives. In an attempt to tackle this issue and develop a more benign flame retardant for PUF, a mica-based nanocomposite was deposited using layer-by-layer assembly. Chitosan (CH) and poly(acrylic acid) (PAA) were used to stabilize high-aspect-ratio mica.

Salt doping to improve thermoelectric power factor of organic nanocomposite thin films.

Thermoelectric materials with a large Seebeck coefficient () and electrical conductivity () are required to efficiently convert waste heat into electricity, but their interdependence makes simultaneously improving these variables immensely challenging. To address this problem, bilayers (BL) of poly(diallyldimethylammonium chloride) (PDDA) and double-walled carbon nanotubes (DWNT), stabilized by KBr-doped poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) were deposited using layer-by-layer (LbL) assembly. Doping PEDOT:PSS with KBr, prior to DWNT dispersion and LbL assembly, results in a six-fold improvement in electrical conductivity with little change in the Seebeck coefficient.

Enzymatic Modification of Polyamide for Improving the Conductivity of Water-Based Multilayer Nanocoatings.

Enzymatic modification, using a protease from (Subtilisin A), was carried out on polyamide 6.6 (PA6.6) fabric to make it more amenable to water-based nanocoatings used to impart electrical conductivity.

Unusually fast and large actuation from multilayer polyelectrolyte thin films.

Polymers responsive to external stimuli (e.g., electric field, chemical vapor, light) are of great interest for smart materials such as sensors and soft robotics.

Transparent Polyelectrolyte Complex Thin Films with Ultralow Oxygen Transmission Rate.

Limiting oxygen permeation through plastic films is important for extending the shelf life of food and flexible electronic devices. Polyelectrolyte complex (PEC) thin films can be used to reduce small molecule diffusion through commodity plastic films. PEC thin films are frequently applied using layer-by-layer assembly, which often requires many processing cycles to deposit a film with desired thickness.

Extraordinary Corrosion Protection from Polymer-Clay Nanobrick Wall Thin Films.

Metals across all industries demand anticorrosion surface treatments and drive a continual need for high-performing and low-cost coatings. Here we demonstrate polymer-clay nanocomposite thin films as a new class of transparent conformal barrier coatings for protection in corrosive atmospheres. Films assembled via layer-by-layer deposition, as thin as 90 nm, are shown to reduce copper corrosion rates by >1000× in an aggressive HS atmosphere.

Polyelectrolyte Multilayer Nanocoating Dramatically Reduces Bacterial Adhesion to Polyester Fabric.

Bacterial adhesion to textiles is thought to contribute to odor and infection. Alternately exposing polyester fabric to aqueous solutions of poly(diallyldimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA) is shown here to create a nanocoating that dramatically reduces bacterial adhesion. Ten PDDA/PAA bilayers (BL) are 180 nm thick and only increase the weight of the polyester by 2.

Carbon-Nanotube-Based Thermoelectric Materials and Devices.

Conversion of waste heat to voltage has the potential to significantly reduce the carbon footprint of a number of critical energy sectors, such as the transportation and electricity-generation sectors, and manufacturing processes. Thermal energy is also an abundant low-flux source that can be harnessed to power portable/wearable electronic devices and critical components in remote off-grid locations. As such, a number of different inorganic and organic materials are being explored for their potential in thermoelectric-energy-harvesting devices.

Fast Self-Healing of Polyelectrolyte Multilayer Nanocoating and Restoration of Super Oxygen Barrier.

A self-healable gas barrier nanocoating, which is fabricated by alternate deposition of polyethyleneimine (PEI) and polyacrylic acid (PAA) polyelectrolytes, is demonstrated in this study. This multilayer film, with high elastic modulus, high glass transition temperature, and small free volume, has been shown to be a super oxygen gas barrier. An 8-bilayer PEI/PAA multilayer assembly (≈700 nm thick) exhibits an oxygen transmission rate (OTR) undetectable to commercial instrumentation (<0.

Combined High Stretchability and Gas Barrier in Hydrogen-Bonded Multilayer Nanobrick Wall Thin Films.

Hydrogen-bonded multilayer thin films are very stretchable, but their gas barrier properties are modest compared to more traditional ionically bonded assemblies. In an effort to improve the gas barrier of poly(ethylene oxide) (PEO)-poly(acrylic acid) (PAA) multilayer films without sacrificing stretchability, montmorillonite (MMT) clay platelets were combined with PAA and alternately deposited with PEO. A ten-bilayer PEO/PAA+MMT film (432 nm thick), deposited on a 1 mm PU substrate, resulted in a 54× reduction in oxygen transmission rate after exposure to a 20% strain.

High Thermoelectric Power Factor Organic Thin Films through Combination of Nanotube Multilayer Assembly and Electrochemical Polymerization.

In an effort to produce effective thermoelectric nanocomposites with multiwalled carbon nanotubes (MWCNT), layer-by-layer assembly was combined with electrochemical polymerization to create synergy that would produce a high power factor. Nanolayers of MWCNT stabilized with poly(diallyldimethylammonium chloride) or sodium deoxycholate were alternately deposited from water. Poly(3,4-ethylene dioxythiophene) [PEDOT] was then synthesized electrochemically by using this MWCNT-based multilayer thin film as the working electrode.