Preparation of a flame-retardant coating based on solvent-free synthesis with high efficiency and durability on cotton fabric

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.

Phosphamide-Based Washing-Durable Flame Retardant for Cotton Fabrics

A formaldehyde-free reactive flame retardant, an ammonium salt of triethylenetetramine phosphoryl dimethyl ester phosphamide phosphoric acid (ATPEPDPA), was synthesized and characterized using nuclear magnetic resonance (NMR). Fourier transform infrared spectroscopy test (FT-IR), durability test and scanning electron microscopy (SEM) results suggested that ATPEPDPA was successfully grafted on cotton fabrics through a -N-P(=O)-O-C covalent bond. Moreover, the limiting oxygen index (LOI) value of 20 wt% ATPEPDPA-treated cotton was 44.6%, which met stringent washing standard after 50 laundering cycles (LCs). The high washing resistance of the ATPEPDPA-treated cotton was due to the p-π conjugation between the N atom and the P(=O) group in the flame-retardant molecule, which strengthened the stability of the -N-P(=O)-O-C bonds between ATPEPDPA and cellulose, and the -N-P(=O)-(O-CH3)2 groups in the ATPEPDPA. The cone calorimetric test showed that the treated cotton had excellent flame retardance. In addition, the TG and TG-IR tests suggested that ATPEPDPA performed a condensed flame retardance mechanism. Furthermore, the physical properties and hand feel of the treated cotton were well maintained. These results suggested that introducing -N-P(=O)-(O-CH3)2 and -N-P(=O)-(ONH4)2 groups into ATPEPDPA could significantly increase the fire resistance and durability of cotton fabrics.

A novel polymer reactive flame retardant for the preparation of highly durable cotton fabrics

A novel polymer ammonium salt of polyethyleneimine phosphate phosphonic acid (APEMPPA) flame retardant for cotton fabrics was synthesized and characterized by nuclear magnetic resonance (NMR), in which some ammonium phosphoric acid groups were replaced by phosphate ester groups to decrease the phenomena that the ammonium ions in flame retardant would exchange with metal ions such as Ca²⁺ and Mg²⁺ in washing water to keep flame retardance well after washing. Energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR) results, and durability of treated cotton fabrics suggested that APEMPPA was grafted onto the cellulose. Limiting oxygen index (LOI) of 40 wt% APEMPPA-treated cotton fabric was 44.5 %, which was still 34.7 % after 50 LCs according to AATCC 61-2013 3A standard. Cone calorimetric and thermogravimetric (TG) results showed the treated cotton fabrics had excellent flame retardancy. TG-FTIR and Raman test results proposed that APEMPPA mainly played a condensed phase flame retardant. EDX results indicated that replacing some ammonium phosphate groups with phosphate ester groups was effective in maintaining flame retardancy during washing. All results showed that increasing the molecular weight and introducing phosphonate group in ammonium phosphorus acid flame retardant can effectively improve flame retardancy and durability. APEMPPA-treated cotton fabrics maintained good tensile strength.

Fabrication of Highly Efficient Flame-Retardant and Fluorine-Free Superhydrophobic Cotton Fabric by Constructing Multielement-Containing POSS@ZIF-67@PDMS Micro-Nano Hierarchical Coatings

The facile construction of a cotton fabric with excellent flame-retardant and water-proof abilities is of great interest for multitask requirements. Herein, a nonfluorine, highly efficient, and cost-effective multifunctional cotton fabric was fabricated via sequentially depositing a novel multielement-containing flame-retardant phosphorylated octa-aminopropyl POSS (PPA-POSS) and a fluorine-free superhydrophobic coating of zeolitic imidazolate framework-67@poly(dimethylsiloxane) (ZIF-67@PDMS). Influences of the PPA-POSS concentration and ZIF-67@PDMS formula on the fire retardancy and water repellency of treated cotton were systematically investigated. The optimized flame-retardant sample CTF3 with 6.2 wt % PPA-POSS exhibited a high limiting oxygen index (LOI) of 34% and self-extinguishing ability. CTF3 was further modified with a properly formulated superhydrophobic ZIF-67@PDMS coating. CTF3-PHB2 displayed enhanced thermal stability, flame retardancy, and outstanding superhydrophobicity. Thermogravimetric analysis (TGA) results demonstrated that CTF3-PHB2 presented a high char residue of 35.9%, which was 220.5% higher than that of the control cotton (11.2%). More importantly, the heat release rate (HRR), total heat release (THR), and average effective heat of combustion (av-EHC) values of CTF3-PHB2 were significantly reduced by 51.4, 56.2, and 68.4%, respectively, compared with those of a pure cotton fabric. Moreover, CTF3-PHB2 showed superhydrophobicity (WCA > 159.3°) and good mechanical abrasion resistance. In addition, CTF3-PHB2 also showed protective abilities such as antifouling, self-cleaning, and water/oil separation performances even for strong acid/alkali mixtures. Thereby, it is believed that the PPA-POSS@ZIF-67@PDMS coating is promising for application in multifunctional textile materials.

Chitosan/sodium polyborate based micro-nano coating with high flame retardancy and superhydrophobicity for cotton fabric

In this work, a sustainable flame retardant and superhydrophobic cotton fabric was prepared by a two-step process: the cotton fabric was firstly treated with a chitosan/sodium polyborate polyelectrolyte complex water solution to obtain a flame retardant layer, and then treated with a polydimethylsiloxane (PDMS) tetrahydrofuran solution to construct a superhydrophobic layer. The phase-separated chitosan with a micro-nano roughness structure was covered by PDMS, which synergistically improved the hydrophobicity of the cotton fabric. The flammability evaluation indicated that the limiting oxygen index value of the treated fabric was increased to 40.0% from 18.2%, the peak of heat release rate was reduced by 63.8%, and the total heat release was reduced by 57.6% compared with that of the control sample. The enhanced flame retardancy was attributed to the excellent charring ability in the condensed phase. The treated fabric also showed anti-sticking, self-cleaning, and oil/water-separating properties. This coating treatment without any F, Cl, Br, P elements involved is regarded as a clean methodology for producing flame retardant and superhydrophobic cotton fabrics.

High-efficiency durable flame retardant with ammonium phosphate ester and phosphine oxide groups for cotton cellulose biomacromolecule

Cotton fibers mainly consist of cellulose biological macromolecule, and its exceedingly flammable nature has severely restricted its application in the fields requiring flame retardancy. To endow cotton fabric with excellent flame retardancy and superior durability, a high-efficiency durable flame retardant (THPO-P) with ammonium phosphate ester and phosphine oxide groups was synthesized and chemically bonded to cotton fabric through padding-baking method. THPO-P showed high flame-retardant efficiency, and the add-on of 5.9% was sufficient to prepare cotton fabric with self-extinguished feature. With the add-on of 19.9%, treated fabric possessed excellent fire safety and durability. The total heat release and peak heat release rate values reduced by 77.1% and 91.8% in contrast to pristine fabric, respectively. Its LOI value still reached up to 33.4% even after 50 laundering cycles, which was far beyond the flame-retardant standard. THPO-P played flame-retardant role by restraining the release of flammable volatiles, liberating nonflammable gases and promoting the char formation during combustion. The flame-retardant treatment deteriorated the tensile strength, whiteness and softness of cotton fabric.

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.

Preparation of a novel functionalized magnesium-based curing agent as an intrinsic flame retardant for epoxy resin

In this study, a novel organic-inorganic hybrid flame retardant 10-(1,4-dicarboxylic acid magnesium salt)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DMMH) was synthesized via neutralization and addition reaction of maleic acid, magnesium hydroxide and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), and subsequently used in an intrinsic flame retardant epoxy resin. The chemical structure and morphology of DMMH were analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Further, the prepared DMMH was combined with ammonium polyphosphate (APP) to form an intumescent flame retardant system. The thermal stability and flame retardance were evaluated by thermogravimetric analysis (TG), UL-94 vertical burning test, limiting oxygen index (LOI) and cone calorimetry. It was observed that the addition of 1.7% DMMH and 5.3% APP led EP-7 to acquire UL-94 V-0 rating, with the limiting oxygen index of 26.0%. As compared with pure EP, the peak heat release rate, total heat release, smoke production rate and total smoke production of the sample was noted to decrease by 54.5%, 35.1%, 43.6% and 38.1%, respectively. In addition, the introduction of DMMH did not negatively impact the mechanical properties of the epoxy resin.