A Superior Two-Dimensional Phosphorus Flame Retardant: Few-Layer Black Phosphorus

Abstract

The usage of flame retardants in flammable polymers has been an effective way to protect both lives and material goods from accidental fires. Phosphorus flame retardants have the potential to be follow-on flame retardants after halogenated variants, because of their low toxicity, high efficiency and compatibility. Recently, the emerging allotrope of phosphorus, two-dimensional black phosphorus, as a flame retardant has been developed. To further understand its performance in flame-retardant efficiency among phosphorus flame retardants, in this work, we built model materials to compare the flame-retardant performances of few-layer black phosphorus, red phosphorus nanoparticles, and triphenyl phosphate as flame-retardant additives in cellulose and polyacrylonitrile. Aside from the superior flame retardancy in polyacrylonitrile, few-layer black phosphorus in cellulose showed the superior flame-retardant efficiency in self-extinguishing, ~1.8 and ~4.4 times that of red phosphorus nanoparticles and triphenyl phosphate with similar lateral size and mass load (2.5~4.8 wt%), respectively. The char layer in cellulose coated with the few-layer black phosphorus after combustion was more continuous and smoother than that with red phosphorus nanoparticles, triphenyl phosphate and blank, and the amount of residues of cellulose coated with the few-layer black phosphorus in thermogravimetric analysis were 10 wt%, 14 wt% and 14 wt% more than that with red phosphorus nanoparticles, triphenyl phosphate and blank, respectively. In addition, although exothermic reactions, the combustion enthalpy changes in the few-layer black phosphorus (−127.1 kJ mol−1) are one third of that of red phosphorus nanoparticles (−381.3 kJ mol−1). Based on a joint thermodynamic, spectroscopic, and microscopic analysis, the superior flame retardancy of the few-layer black phosphorus was attributed to superior combustion reaction suppression from the two-dimensional structure and thermal nature of the few-layer black phosphorus.

Research Progress on the Preparation Methods for and Flame Retardant Mechanism of Black Phosphorus and Black Phosphorus Nanosheets

“…Further- Black phosphorus alone has a limited effect as a flame retardant. Some scholars have added synergistic flame retardants to enhance the flame retardant effect of black phosphorus [93,94]. Yin et al [95] added hexagonal boron nitride (BN), another flame retardant, to the BP/WPU system to create a new BP/BN/WPU composite material.…”

Theoretical Study on the P–C Bond Dissociation Enthalpy in 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide Flame Retardants

“…Over the past few decades, phosphorus-containing flame retardants (FRs) have been widely utilized in rigid polyurethane foams, polypropylene (PP), and epoxy resins due to their superior flame-retardant efficiency, low toxicity, and low smoke emissions. , Among phosphorus-based flame retardants, DOPO-type flame retardants have become the focus because of their high flame-retardant performance and excellent molecular design capabilities. One kind of phosphorus-containing FRs is the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) derivatives, , which results from the replacement of P–H bonds with P–C bonds through nucleophilic addition, nucleophilic substitution, and molecular rearrangement, and the incorporation of P–C bonds can enhance the flame-retardant performance to a superior level .…”

High-Performance Infrared Detectors Based on Black Phosphorus/Carbon Nanotube Heterojunctions

“…The light absorption characteristics of BP shows that BP is a good infrared light-absorbing material [7,8]. Additionally, BP also exhibits good strength, flexibility, and flame retardation [9,10]. Similarly, SWCNTs have a direct tunable bandgap that varies with their diameter [11,12], showing strong photo-absorption range from ultraviolet to infrared [12,13] and a fast light response capability [14].…”