Flame-Retardant and Self-Healing Waterborne Polyurethane Based on Organic Selenium

Abstract

Waterborne polyurethane has drawn extensive attention due to its environmental friendliness and is widely used in many areas. However, it is still a great challenge to synthesize waterborne polyurethanes with flame retardancy and fast roomtemperature self-healing ability, along with excellent mechanical performance and emulsion stability due to the mutually contradictory nature of these properties. Herein, waterborne polyurethanes containing organic selenium (SWPU-x) from 0.67 to 3.28 wt % were synthesized, which could simultaneously realize flame retardancy and self-healing ability based on the ability to scavenge active free radicals at high temperature and the dynamic switch of diselenide. All these SWPU-x films self-extinguished within 1 s after the ignition in the vertical combustion tests. The limiting oxygen index of SWPU-4 was improved to 28.5% with excellent UL-94 level (V-0) and self-healing efficiency (91.25%, after being healed in the photoreactor for 30 min at room temperature), together with high mechanical properties (tensile strength was 18.5 MPa and elongation at break was 869.63%), and the total heat release (THR) for SWPU-4 (49.28 MJ/m 2 ) could decrease to 23.80% of the THR for the original waterborne polyurethane WPU (64.67 MJ/m 2 ). This work discovered a new flame-retardant element (organic selenium) and studied its flame-retardant behaviors and self-healing function simultaneously, which would extremely extend the application of waterborne polyurethanes.

Tough and Self-Healing Waterborne Polyurethane Elastomers via Dynamic Hydrogen Bonds Design for Flexible Conductive Substrate Applications

“…However, the weak dynamic nature of the internal crystallinity, entanglement, and strong covalent bonds often hinder the migration ability of polymer chains, making it difficult to achieve self-repairing performance. − In recent years, there has been extensive research and reporting on incorporating reversible bonds into polymer chains to confer repairability to materials. These include covalent reversible bonds, such as disulfide bonds, , Diels–Alder (D–A) reactions, , boronic ester bonds, , acyl hydrazone bonds, and diselenide bonds, as well as noncovalent reversible bonds, such as hydrogen bonds, coordination bonds, π–π stacking, − ionic bonds, and others . Among them, the hydrogen bond is a type of dipole–dipole interaction, and its strength depends on the nature of the donor and acceptor.…”

“…10−13 In recent years, there has been extensive research and reporting on incorporating reversible bonds into polymer chains to confer repairability to materials. These include covalent reversible bonds, such as disulfide bonds, 14,15 T h i s c o n t e n t i s Diels−Alder (D−A) reactions, 16,17 boronic ester bonds, 18,19 acyl hydrazone bonds, 20 and diselenide bonds, 21 as well as noncovalent reversible bonds, such as hydrogen bonds, 22 coordination bonds, 23 π−π stacking, 24−26 ionic bonds, and others. 27 Among them, the hydrogen bond is a type of dipole− dipole interaction, and its strength depends on the nature of the donor and acceptor.…”

Photoluminescent Self-Healable Waterborne Polyurethane/Mo and S Codoped Graphitic Carbon Nitride Nanocomposite with Bioimaging and Encryption Capability

“…These bonds should have the capability to undergo easy breakage and reformation, facilitating the recovery of the material’s network structure. Ionic interactions, Diels–Alder reactions, oxime bonds, diselenide bonds, B–O bonds, disulfide bonds, and Schiff bases, which are dynamic covalent bonds, have been commonly employed in formulating healable and recyclable SHWPU. Again, certain research studies have suggested that incorporating hydrogen bonds can enhance the mechanical strength of self-healing polyurethane elastomers .…”

Photochemical Transformations of Peptides Containing the N-(2-Selenoethyl)glycine Moiety

“…Visible light can be employed for a wide range of compounds, including small diselenides and polymers. , Due to the low bond energy of the Se–Se bond, visible light can easily break the diselenide bond without the need for a catalyst, making diselenide metathesis compatible with biological systems. This property of Se–Se bonds has paved the way for the development of dynamic systems with properties such as self-healing, − shape memory, and so on …”