Abstract: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.
“… Figure A shows the dynamic TGA curve of PDA obtained by a temperature scan from 25 to 600 °C at 10 °C min –1 . In agreement with what has been previously reported, ,− no sharp mass loss is observed with increasing temperature. Instead, PDA gradually loses mass upon increasing the temperature in what appears to be three temperature regimes with different mass loss slopes, i.e., ∼25–75 °C, ∼75–300 °C, and 300–600 °C.…”
Control over adhesion at interfaces from strong bonding to release between thermoplastic polymers (TPs) and metal oxides is highly significant for polymer composites. In this work, we showcase a simple and inexpensive method to tune adhesion between a TP of growing interest, poly(lactic acid) (PLA), and two commercial metal alloys, based on titanium and stainless steel. This is realized by coating titanium and stainless steel wires with polydopamine (PDA), thermally treating them under vacuum at temperatures ranging from 25 to 250 °C, and then comolding them with PLA to form pullout specimens for adhesion tests. Pullout results indicate that PDA coatings treated at low temperatures up to a given threshold significantly improve adhesion between PLA and the metals. Conversely, at higher PDA annealing temperatures beyond the threshold, interfacial bonding gradually declines. The excellent control over interfacial adhesion is attributed to the thermally induced transformation of PDA. In this work, we show using thermogravimetric analysis, X-ray photoelectron spectroscopy, Fourier transform infrared, and 13 C solid-state NMR that the extent of the thermal transformation is dependent on the annealing temperature. By selecting the annealing temperature, we vary the concentration of primary amine and hydroxyl groups in PDA, which influences adhesion at the metal/PLA interface. We believe that these findings contribute to optimizing and broadening the applications of PDA in composite materials.
“… Figure A shows the dynamic TGA curve of PDA obtained by a temperature scan from 25 to 600 °C at 10 °C min –1 . In agreement with what has been previously reported, ,− no sharp mass loss is observed with increasing temperature. Instead, PDA gradually loses mass upon increasing the temperature in what appears to be three temperature regimes with different mass loss slopes, i.e., ∼25–75 °C, ∼75–300 °C, and 300–600 °C.…”
Control over adhesion at interfaces from strong bonding to release between thermoplastic polymers (TPs) and metal oxides is highly significant for polymer composites. In this work, we showcase a simple and inexpensive method to tune adhesion between a TP of growing interest, poly(lactic acid) (PLA), and two commercial metal alloys, based on titanium and stainless steel. This is realized by coating titanium and stainless steel wires with polydopamine (PDA), thermally treating them under vacuum at temperatures ranging from 25 to 250 °C, and then comolding them with PLA to form pullout specimens for adhesion tests. Pullout results indicate that PDA coatings treated at low temperatures up to a given threshold significantly improve adhesion between PLA and the metals. Conversely, at higher PDA annealing temperatures beyond the threshold, interfacial bonding gradually declines. The excellent control over interfacial adhesion is attributed to the thermally induced transformation of PDA. In this work, we show using thermogravimetric analysis, X-ray photoelectron spectroscopy, Fourier transform infrared, and 13 C solid-state NMR that the extent of the thermal transformation is dependent on the annealing temperature. By selecting the annealing temperature, we vary the concentration of primary amine and hydroxyl groups in PDA, which influences adhesion at the metal/PLA interface. We believe that these findings contribute to optimizing and broadening the applications of PDA in composite materials.
“…Multiple nonflammable gases are identified around 300 °C in both the base recipe and phosphoric acid-doped coating including NH 3 (17 amu), H 2 O (18 amu), N 2 (28 amu), and CO 2 (44 amu), as seen in Figure . The uncoated foam’s reduced peak at 28 amu can be attributed to CO production, while the distinct peak of both coated samples around 327 °C is N 2 being released with the addition of CH. − The phosphoric-doped coating shows a 10 °C delay in the release of these gases, as well as an increased intensity of the peak. These gas decomposition products act to dilute the oxygen-rich environment that perpetuates the fire.…”
Soft furnishing fires contribute to 29% of fire causalities and $8.7 billion in direct property damage annually in the United States. Polyurethane foam (PUF), a common component in soft furnishings known for its comfort and flexibility, can emit toxic gases and propagate fires due to melt dripping when ignited. Various acid salts were added to a layer-by-layer assembled nanocoating, consisting of chitosan and carboxymethyl cellulose, to improve PUF flame retardancy and to understand the influence of salt-doping on flammability. The 20-bilayer phosphoric acid-doped coating exhibits a self-extinguishing behavior, with a 67% reduction in peak heat release rate while maintaining the structural integrity of the foam. By depositing this completely environmentally sourced coating on PUF, the inherent danger of soft furnishing fires can be significantly reduced in a nontoxic manner.
“…1 b. After polymerization, the product peaks broaden due to the oligomeric nature of polydopamine and a new peak is observed downfield that correlates to quinone and 5,6-dihydroxyindole (DHI) formation that occurs due to oxidation of dopamine 22 . Figure 1 ( a ) 13 C solid-state CP-MAS NMR spectra for dopamine hydrochloride and synthesized polydopamine.…”
The reduction of interfacial interaction and the deterioration of processing properties of aluminum hydrides (AlH3) is the main challenges preventing its practical application. Here, a simple and effective core–shell structure aluminum hydrides@polydopamine (AlH3@PDA) complex was constructed through in-situ polymerization. The evolution of element states on the surface of AlH3 conducted by X-ray photoelectron spectroscopy indicated the successful introduction of PDA to form the core@shell structure, the thickness of the PDA coated layer increased with the increasing PDA dosage from 0.1 to 1.6% in mass fraction, and the maximum of thickness is 50 nm in TEM testing. Py GC/MS results proved that the increase of dopamine concentration leads to higher proportions of self-assemble units, whereas lower dopamine concentrations favor higher levels of chemical bonded components. Regarding whether PDA is a covalent polymer or a noncovalent aggregate of some species, the formation of intermediates, such as dopaminechrome and 5,6-dihydroxyindole played an important role to coordination interaction with AlH3 in FTIR, Raman, and UV–Vis spectra testing. Compared with pure AlH3, the formation of organic PDA coating improved AlH3 heat resistance. The adhesion work with GAP adhesive was also improved from 107.02 J/m2 of pure AlH3 to 111.13 mJ/m2 of AlH3@PDA-5 complex. This paper provides well support for further practical application of AlH3 in solid propellants.
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