In this manuscript, natural materials were combined into a single "pot" to produce flexible, highly fire resistant, and bioinspired coatings on flexible polyurethane foam (PUF). In one step, PUF was coated with a fire protective layer constructed of a polysaccharide binder (starch or agar), a boron fire retardant (boric acid or derivative), and a dirt char former (montmorillonite clay). Nearly all coatings produced a 63% reduction in a critical flammability value, the peak heat release rate (PHRR). One formulation produced a 75% reduction in PHRR. This technology was validated in full-scale furniture fire tests, where a 75% reduction in PHRR was measured. At these PHRR values, this technology could reduce the fire threat of furniture from significant fire damage in and beyond the room of fire origin to being contained to the burning furniture. This flammability reduction was caused by three mechanisms-the gas-phase and condensed-phase processes of the boron fire retardant and the condensed-phase process of the clay. We describe the one-pot coating process and the impact of the coating composition on flammability.
Imprint lithography has been explored as a method to transfer arrays of patterned features onto pure polymers and polymer/metallic nanoparticle composites. Despite the success of this method for those materials, it has never been achieved on the sub-micron scale with polymer-oxide particle hybrids. This study patterns ZnO-PMMA (poly(methyl methacrylate)) hybrids via imprint lithography from co-suspensions of PMMA and ZnO nanoparticles in anisole from 1 vol% to 20 vol% ZnO solids loading. ZnO nanoparticles are functionalized with nonanoic acid to disperse the nanoparticles in anisole with dissolved PMMA. The feature fidelity of the patterned arrays decreases with increasing ZnO content, indicating an increase in particle agglomeration as the ZnO particle content increases. Feature size, ZnO content, and ZnO nanoparticle agglomeration are critical factors influencing the photoluminescence (PL) intensity. The ZnO solids loading at a 500 nm feature size needs to be 10 vol% or higher for the enhanced PL response. When the ridge size increases to 1 μm, ZnO solids loading as low as 1 vol% is feasible. This method of lithographic patterning of nanoparticle-polymer suspensions can be applied to a wide variety of hybrid devices and has the potential to open many applications including optical devices and biomedical screening.
Aqueous nanoparticle dispersions have been widely studied for their important industrial applications, including photocatalyst, coating, and casting. However, much less work has been conducted on nanoparticle dispersions in organic solvents, especially when co-dispersing with dissolved polymers. In this study, we explore TiO 2 / ZnO nanoparticle and poly(methyl methacrylate) (PMMA) co-dispersion in organic solvent anisole. To achieve uniformly dispersed suspensions, nanoparticle surface functionalization with nonanoic acid and 1-pentanol is conducted. Nonanoic acid has higher surface coverage on TiO 2 and the two dispersants show similar surface coverage on ZnO. Heat treatment enhances the dispersant adsorption on the nanoparticle surfaces. For both TiO 2 / PMMA and ZnO/PMMA co-dispersions, higher solids loading leads to higher suspension viscosity. Higher volume fraction of nanoparticles in the nanoparticle plus PMMA solid phase results in lower viscosity, mainly by reducing the entanglement of the dissolved PMMA chains.
Imprint lithography has been explored as a method to transfer arrays of patterned features onto pure polymers and polymer/metallic nanoparticle composites. However, it has never been achieved on the submicrometer scale with polymer–oxide particle hybrids. This study uses in situ polymerization and imprint lithography to form ZnO–PMMA hybrid patterns. The polymerization temperature is varied to study its effects on feature fidelity, film flexibility, and pattern photoluminescence (PL) response. For a given polymerization temperature, the feature fidelity decreases with increasing ZnO content according to line-edge roughness (LER), inverse circularity (IC), and surface roughness (SR) measurements. This decrease in feature fidelity indicates an increase in particle agglomeration as the ZnO content increases. The elongation at failure for the hybrids decreases with the polymerization temperature and the ZnO content while the bending radius increases. Even at the lowest feature fidelity, the LER is <10% of the feature size, the IC is <2, and the SR is <75 nm. The patterned features increase the PL intensity and demonstrate the potential for flexible optical devices.
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