Construction of Charring-Functional Polyheptanazine towards Improvements in Flame Retardants of Polyurethane

Construction of efficient and environmentally friendly bio-based flame retardant cotton fabric through layer by layer self-assembly of alkylammonium functional silsesquioxane/phosphorylated sodium alginate

As an important source of green cleaning flame retardants, bio-based materials have been widely studied by researchers. However, the development of efficient biobased flame retardants and convenient finishing methods was of great significance for the functional finishing of materials. Herein, a convenient and efficient flame retardant cotton fabric was prepared via layer by layer self-assembly (LbL) by alternating precipitation of a novel bio-based flame retardant phosphorylated sodium alginate (PSA) and alkylammonium functionalized siloxane (A-POSS). The effect of coating number on flame retardancy and thermal properties of coated cotton fabric was systematically studied. Thermogravimetric analysis (TGA) results showed that residual char contents of AP/PS-15BL under air and N2 atmospheres increased by 252.0% and 225.2%, respectively, compared with control cotton. In vertical flammability tests, both the AP/PS-10BL and AP/PS-15BL showed self-extinguishing behavior and successfully passed the UL-94 V-0 rating. More importantly, the LOI value of AP/PS-15BL was significantly increased to 35.0% from 20.0% of pure cotton fabric. Additionally, coated samples showed good mechanical properties and washable resistance. In CONE test, the peak heat release rate (PHRR) and total heat release rate (THR) of AP/PS-15BL decreased by 89.3% and 49.3% respectively, compared with control cotton. Therefore, this green and convenient flame-retardant finishing method has great application potential in the multi-functional finishing of cotton fabrics.

Characterization and Flame-Retardant Properties of Cobalt-Coordinated Cyclic Phosphonitrile in Thermoplastic Polyurethane Composites

Halogen-free organophosphorus flame retardants have promising application prospects due to their excellent safety and environmental protection properties. A cobalt-coordinated cyclic phosphonitrile flame retardant (Co@CPA) was synthesized via a hydrothermal method using hexachlorocyclotriphosphonitrile (HCCP), 5-amino-tetrazolium (5-AT), and cobalt nitrate hexahydrate (Co(NO3)2∙6H2O) as starting materials. The structure was characterized using Fourier transform infrared (FTIR), nuclear magnetic resonance spectroscopy (1H-NMR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Thermoplastic polyurethane (TPU) composites were prepared by incorporating 10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphame-10-oxide (ODOPB), Co@CPA, and silicon dioxide (SiO2) via melt blending. The flame-retardant performance and thermal stability of the TPU composites were evaluated through limiting oxygen index (LOI), vertical combustion (UL-94), TG, and cone calorimetric (CCT) tests. SEM and Raman spectroscopy were used to analyze the surface morphology and structure of the residual carbon. A synergistic flame-retardant effect of ODOPB and Co@CPA was observed, with the most effective flame retardancy achieved at a TPU:ODOPB:Co@CPA:SiO2 ratio of 75:16:8:1. This composition exhibited an LOI value of 26.5% and achieved a V-0 rating in the UL-94 test. Furthermore, compared to pure TPU, the composite showed reductions in total heat release, CO production, and CO2 production by 6.6%, 39.4%, and 48.9%, respectively. Our research findings suggest that Co@CPA demonstrates outstanding performance, with potential for further expansion in application areas. Different metal-based cyclic phosphonitrile compounds are significant in enriching phosphorus-based fine chemicals.