Fire-Resistant Flexible Polyurethane Foams via Nature-Inspired Chitosan-Expandable Graphite Coatings

Abstract

The current methods used to impart flameretardant or fire-resistant properties to flexible polyurethane foams (PUFs) to meet fire safety requirements entail the use of halogenated phosphorus-based compounds. Whereas these are highly effective as flame retardants, the associated toxicity derived from halogens in the burning fumes are deadly. To address this problem, we herein present a facile and efficient method of fabricating highly fire-resistant flexible PUF using halogen-free nature-inspired coatings. All of the active ingredients used to fabricate the coatings originated from natural or widely available sources: chitosan from crustacean shells, acetic acid that is found in vinegar, and expandable graphite mined from mineral rocks, thus making this strategy environmentally friendly and sustainable. These coatings offer excellent flame-retardant properties; with a limiting oxygen index (LOI) value as high as 31%, the coated foam could potentially pass the highest levels within the British Standard 5852, which is a commonly accepted global industry standard for meeting the fire safety requirement of flexible PUF. Furthermore, cone calorimeter testing revealed the superior fire safety performance of the coated foam, including very low heat and smoke release upon burning. The flame retardancy of the coated PUFs is tunable depending on the amount of graphite employed in the coating solutions. It is anticipated that the coating strategy described here is applicable to other substrates.

Polyurethane Foams Coated with Phosphorus-Doped Mesoporous Carbon for Flame-Retardant Triboelectric Nanogenerators

“…The CH/AL alone coatings exhibited slightly higher pkHRR values than that of neat PUF (Figure S7), which is believed to be due to the flammability of the biopolymers. , Hence, the contribution of CH and AL to the flame retardancy of PUF is insufficient, except for acting as effective film-forming agents in the binding of PMC to the surface of the PUF. Usually, non-intumescent polymer-based FR coatings are not effective for PUF unless they are combined with an appropriate amount of particle-based, i.e., clay or carbon FRs. , Other LbL-deposited FRs on PUF, such as CH/GO and CH/ammonium polyphosphate, have also led to a decrease in pkHRR reduction upon increasing the number of bilayers. , Overall, the results showed that the PMC-filled coating significantly reduced pkHRR, one of the most important fire safety metrics that represents the point in a fire where the flame likely propagates to adjacent flammable materials. A lower pkHRR value implies a lower risk of spreading to neighboring flammable items, thereby providing more time for evacuation from a real fire incident .…”

“…Usually, non-intumescent polymer-based FR coatings are not effective for PUF unless they are combined with an appropriate amount of particlebased, i.e., clay or carbon FRs. 1,46 Other LbL-deposited FRs on PUF, such as CH/GO and CH/ammonium polyphosphate, have also led to a decrease in pkHRR reduction upon increasing the number of bilayers. 4,22 Overall, the results showed that the PMC-filled coating significantly reduced pkHRR, one of the most important fire safety metrics that represents the point in a fire where the flame likely propagates to adjacent flammable materials.…”

Soft Liquid Metal Infused Conductive Sponges

“…Notably, the hysteresis loops observed in liquid state were smaller and more stable than that in solid state due to the reduced buckling and decreased frictions in the sponge matrices in the liquid state, and also possibly minimizing mechanical damages across the composite structures, such as cracks. [ 37c,45 ]…”

It Takes Two to Tango: Synergistic Expandable Graphite–Phosphorus Flame Retardant Combinations in Polyurethane Foams

“…Chitosan, shown in Figure 13d, is a fibrous compound extracted from crustacean shells. Wong et al [114] coated FPUFs with chitosan and EG using single-step coating. In the cone calorimeter measurements, the combination of chitosan and EG in FPUFs significantly reduced the PHRR, THR, and TSR.…”