Polyelectrolyte Complex with Controllable Viscosity by Doping Cu2+ Protects Nylon-Cotton Fabric against Fire

Ethanol-induced ammonium polyphosphate-silver gel paint: breaking the trade-off between conductivity, flame retardancy and adhesion in single-layer functional coatings

Electrical fires pose significant threats to the lives and property safety of people. Although utilizing coatings to impart conductivity and flame retardancy to materials is convenient and reliable, traditional layer-by-layer preparation methods have the limitations of cost, convenience and scalability. Therefore, a single-layer coating that simultaneously imparts excellent conductivity and flame retardancy to materials presents broader application prospects. And good adhesion of the coating is another essential aspect. However, the trade-off between conductivity, flame retardancy, and adhesion creates huge challenges in the development of such coatings. Here, we report an ethanol-induced ammonium polyphosphate-silver (APP-Ag) gel paint to completely address the above issues. High molecular weight APP served as both a flame retardant and an adhesive, while the coordinating action of phosphate groups ensured the effective dispersion of nanosilver, and the nitrogen-containing carbon layer formed from triethanolamine and ascorbic acid at high temperature significantly enhanced the conductivity of the coating by connecting the silver nanoparticles. The coated materials could exhibit an electrical conductivity of over 200 S m-1, with the limiting oxygen index (LOI) exceeding 60%. Meanwhile, the peak heat release rate (PHRR) and total heat release (THR) decreased by more than 30% compared to those of the untreated materials. Additionally, we utilized this gel paint to fabricate electric heating fabrics, motion sensors, and fire alarm devices. Finally, we have thoroughly explored the potential mechanisms of conductivity, flame retardancy, and adhesion of the gel coatings.

Biopolymer-Based Flame Retardants and Flame-Retardant Materials

Polymeric materials featuring excellent flame retardancy are essential for applications requiring high levels of fire safety, while those based on biopolymers are highly favored due to their eco-friendly nature, sustainable characteristics, and abundant availability. This review first outlines the pyrolysis behaviors of biopolymers, with particular emphasis on naturally occurring ones derived from non-food sources such as cellulose, chitin/chitosan, alginate, and lignin. Then, the strategies for chemical modifications of biopolymers for flame-retardant purposes through covalent, ionic, and coordination bonds are presented and compared. The emphasis is placed on advanced methods for introducing biopolymer-based flame retardants into polymeric matrices and fabricating biopolymer-based flame-retardant materials. Finally, the challenges for sustaining the current momentum in the utilization of biopolymers for flame-retardant purposes are further discussed.

Self-assembled lignin-based flame retardant hybrids carrying Cu2+ for poly(lactic acid) composites with improved fire safety and mechanical properties

To enhance the flame retardancy and mechanical performance of PLA, a polyelectrolyte complex predicated on lignin was obtained by electrostatic mutual adsorption of ammonium polyphosphate (APP), polyethyleneimine (PEI), and copper ions as raw materials. The FT-IR spectra and EDX analysis confirmed the successful synthesis of a lignin-based flame retardant hybrid (APL-Cu2+) containing copper, phosphorus, and nitrogen elements. The combustion test results showed that the peak heat release rate and total heat release of the PLA composite containing 12 wt% APL-Cu2+ were decreased by 15.1 % and 18.2 %, respectively, as compared to those of pure PLA. The char residue morphology observation revealed that the addition of APL-Cu2+ could promote the formation of a highly dense and stable graphitized char layer, while TG-MS detected the emission of refractory gases such as ammonia gas, carbon dioxide, and water during combustion. The strong hydrogen bonding between APL-Cu2+ and the PLA matrix kept the composite maintaining good strength and toughness. The tensile strength and impact strength of PLA/6APL-Cu2+ increased by 4.73 % and 65.71 %, respectively, due to its high crystallinity and good interfacial compatibility. This work provides a feasible method to develop biobased flame retardant hybrids for PLA composites with better fire safety and improved mechanical properties.

Bio-based phytic acid@polyurushiol‑titanium complex coated cotton fabrics with durable flame retardancy for oil-water separation

Bio-based hydrophobic coating modified cotton fabrics with durable flame retardancy are of high interest in the application of oil-water separation for not only avoiding the use of hazardous substances but also improving the fire safety during use. Herein, phytic acid@Polyurushiol‑titanium complex coated cotton fabric was developed using the facile dip-coating method involving the sequential immersion in the solution of poly(ethyleneimine), phytic acid, titanium oxide, and urushiol. The underlying coating accommodated abundance of phytic acid, which imparted excellent flame retardancy to cotton fabric, and the top coating composed of the polyurushiol‑titanium complex endowed cotton fabric with high hydrophobicity that the water contact angle (WCA) was up to 149.8°. The hydrophobicity also guaranteed effective protection of the underlying phytic acid against chemical solvents and abrasion. Besides, the hydrophobic coating allowed cotton fabric for good self-cleaning and effective oil-water separation. Therefore, the preparation of phytic acid@polyurushiol‑titanium complex coated cotton fabric offers a promising approach to construct durable biomass-coated cellulose-based fabric with multifunctionality.