Facile synthesis of a high efficiency and durability L-citrulline flame retardant for cotton.

A novel flame retardant (FR), the ammonium salt of citrulline-penta (methylphosphonic acid) (ACPMPA) based on L-citrulline was synthesized, and its structure was characterized by 13C, 1H, and 31P nuclear magnetic resonance (NMR) spectroscopy. The ACPMPA flame retardant molecule contains five ammonium salts of phosphorus acid and one ammonium salt of carboxylic acid, which allowed the covalent attachment of ACPMPA onto cellulose via -P=O(-O-C) and -COOC bonds. The results showed that the treated cotton fabrics had very high flame retardance and excellent durability. The limiting oxygen index (LOI) of cotton fabric treated with 35%-ACPMPA reached 49.2% and only decreased to 34.2% after 50 laundry cycles. Vertical flame tests also demonstrated that the treated cotton fabric acquired good flame retardance. The thermogravimetry (TG) and TG-IR results showed that the treated cotton left more residues and released almost no flammable volatiles at high temperatures. The cone calorimetry results showed that the treated cotton released less heat than pure cotton. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) results demonstrated that the structure of the treated cotton fabric was almost unchanged, and no free formaldehyde was detected, indicating that the treated cotton was safe. The treated cotton fabric also retained good tensile strength and whiteness.

An eco-friendly NP flame retardant for durable flame-retardant treatment of cotton fabric.

A halogen-free, formaldehyde-free, efficient, durable, NP flame retardant, the ammonium salt of meglumine phosphoric ester acid (ASMPEA), was prepared. The Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (1H NMR, 13C NMR, and 31P NMR) results indicated that ASMPEA was grafted onto cotton fibers by P-O-C covalent bonds. The LOI value of 30 wt% ASMPEA-treated cotton fabric was 40.2%, and after 50 laundering cycles (LCs), the LOI value decreased to 29.4%, indicating that the cotton fibers treated with ASMPEA were endowed with excellent durable flame retardancy. Thermogravimetry (TG), cone calorimetry, and vertical flammability test results showed that ASMPEA-treated cotton decomposed into phosphoric acid or polyphosphoric acid during combustion, which promoted the thermal degradation and charring of treated cotton fabrics and hindered the spread of flames. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive spectrometry (EDS) verified that ASMPEA infiltrated the cotton fiber without obviously affecting its surface morphology or crystal structure; however, the mechanical properties of the treated cotton fabric decreased slightly. These results confirm that ASMPEA achieved excellent durable flame retardancy when used to coat cotton fabric.

A high molecular weight formaldehyde-free polymer flame retardant made from polyvinyl alcohol for cellulose.

Polyvinyl alcohol and phosphoric acid were used as primary raw materials to synthesize a polyvinyl alcohol/ammonium phosphate flame retardant (PVAAP) for cotton fabrics. The limiting oxygen index of the cotton fabric treated with 24% PVAAP was 42.1. After 50 standard laundry cycles, the limiting oxygen index remained relatively high (26.3), suggesting that the 24% PVAAP can be used as a durable flame retardant. The vertical flammability test of the cotton fabric treated with PVAAP exhibited no afterflame and afterglow. The cone calorimetry test indicated that the peak of the heat release rate and total heat release of the cotton fabric treated with 24% PVAAP were significantly lower than those of the control cotton. Thermogravimetric and thermogravimetric-infrared spectroscopy revealed that the initial decomposition temperature of the PVAAP-treated fabric was substantially lower than that of the control fabric, and more residual carbon was generated. The PVAAP altered the thermal decomposition pathway of the treated cotton. The X-ray diffraction patterns and scanning electron microscopy images suggested that the PVAAP treatment did not change the structure of the fibers.

Facile, one-pot, formaldehyde-free synthesis of reactive NP flame retardant for a biomolecule of cotton.

The NP flame retardant ammonium salt of hydroxyethyl hexahydrotristriazine-triphosphoric acid (AHTTPA) was prepared by a one-pot synthesis method under formaldehyde-free and solvent-free conditions. The AHTTPA was finished on the biomolecule of cotton by using the dip-roll-bake method. Nuclear magnetic resonance (NMR 1H, 13C, and 31P) demonstrated that AHTTPA was successfully synthesized. The flame retardancy of AHTTPA-treated cotton was studied by limiting oxygen index (LOI), vertical flaming test (VFT), scanning electron microscopy (SEM), and cone calorimetry (CC). The results from these tests indicate that AHTTPA-treated cotton exhibited favorable flame retardancy and durability (the LOI value of 40%-treated cotton after 50 laundering cycles (LCs) was 29.8%), the flame was immediately extinguished after removal from the treated cotton, no smoldering or continued burning, the burned part formed a complete carbon frame and generally maintained its original morphology, the peak heat release rate (PHRR) and total heat release (THR) of AHTTPA-treated cotton fabric were significantly lower than pure cotton. Thermogravimetric analysis (TGA) results showed that AHTTPA improved the thermal stability of cotton. The breaking strength and softness of AHTTPA-treated cotton was also retained.