FLAME RETARDANT FOR COTTON FABRICS BASED ON PHOSPHATE ACID-UREA POLYMER

ABSTRACT

A new flame retardant based on urea-phosphoric acid containing a large amount of phosphorus and nitrogen elements was synthesized and successfully applied to cotton fabrics. The resulting flame retardant greatly contributed to the improvement of fire resistance of cotton fabrics. Infrared spectroscopy checked the presence of phosphorus and nitrogen elements in the flame retardant soaked cotton.

АННОТАЦИЯ

Синтезирован и успешно применен на хлопчатобумажных тканях новый антипирен на основе мочевино-фосфорной кислоты, содержащий большое количество элементов фосфора и азота. Полученный антипирен в значительной степени способствовал повышению огнестойкости хлопчатобумажных тканей. Инфракрасная спектроскопия проверила наличие элементов фосфора и азота в пропитанной антипиреном хлопке.

Keywords:Cotton fabrics, combustion ,flame retardant, degradation, phosphoric acid

Ключевые слова: Хлопчатобумажные ткани, горение, антипирены, деградация, фосфорная кислота

Introduction. Cotton is widely distributed in the world as an industrial product, the main raw material of the textile industry. Although there are various new fabrics available in the market now, cotton fabrics are still widely used due to their excellent properties and advantages. These benefits facilitate the use of cotton fabric in versatile textiles such as skin-friendly fabrics such as underwear and children's clothing. However, cotton is a highly flammable material[5,6,9] Flame-resistant cotton fabrics are often used in textiles, clothing, and more. Many studies have been conducted to improve the fire resistance of cotton fabrics[5]. Halogen-based flame retardants are effective and widely used, but ongoing research shows that flame retardants containing halogens, while having good flame retardant properties, produce harmful smoke and toxic corrosive gases when exposed to fire, including can cause serious problems that threaten human health[1,3,7]. Therefore, the demand for effective halogen-free flame retardants is increasing. Instead of halogen-containing flame retardants, more ecologically effective flame retardants are being synthesized[6]

Therefore, it is necessary to continue efforts to develop more environmentally friendly and effective flame retardants. To meet this need, many bio-based flame retardant materials have been explored, including proteins, DNA, and bio-resources combined with phosphorus or nitrogen compounds. For example,[2] used salmon sperm DNA as a natural green flame retardant, which improved the thermal stability and fire resistance of cotton fabrics and increased the oxygen limit index of cotton fabrics by 28%[2].To improve fire resistance, casein and ammonium polyphosphate (APP) are used to create a fire-resistant coating on the surface of cotton fabrics[3]. Their research shows that casein combined with APP-based flame retardant system catalyzes and accelerates the process of dehydration and burning of cotton fabric, but the addition of more than 5% casein reduces the physiological comfort of cotton fabric based on chicken feather protein[3] Synthesized a new flame retardant and applied it to cotton fabric together with boric and boric acid. The processed cotton formed a uniform and dense carbon layer to prevent further degradation during combustion, indicating that the protein-based flame retardant and borax had a synergistic flame retardant effect [4]. In general, halogen-free and phosphorus-containing refractories remain a cost-effective and effective option.

In this study, we tried to synthesize halogen-free flame retardant with synergistic flame retardant effect of P-N with cheap raw materials such as urea, phosphoric acid, and applied it to cotton fabrics to improve fire resistance.

Scheme 1. Synthesis of flame retardants1.

Experience part. Materials: Cotton fabrics . phosphoric acid (85%), urea, ethanolamine.

Synthesis of flame retardants. Urea (12 g, 0.2 mol) was added to the flask and phosphoric acid (85%, 23.05 g) was slowly added and heated at 80⁰C for 4 hours on a magnetic stirrer. Then ethanolamine (12.22 g, 0.2 mol) was added and the reaction between these substances continued for 1 hour at room temperature. Ammonia was released in the reaction. Then we added phosphoric acid (85%, 23.05 g) to the mass in the flask, the reaction continued for 3 hours at a temperature of 140⁰C. After that, urea (12 g, 0.2 mol) was added and the temperature increased to 150⁰C. Continued for 2 hours. As a result of the reaction, a white viscous water-soluble substance was formed. The reaction equation is shown in scheme 1.

Processing of cotton fabric. The cotton fabric was ultrasonically cleaned for 15 minutes and dried at 100 C, then immersed in a flame retardant solution (FR; 15%, 20% or 25%). Then the cotton cloth is washed in distilled water for 1 minute.

Fourier transform infrared spectroscopy (FT-IR). Fourier transform infrared spectroscopy was used to measure the absorption peaks of the characteristic group of cotton fabric and treated cotton fabric. A Fourier transform infrared spectrometer (IR Tracer) equipped with a diamond crystal in ATR mode in the range of 4000-400 cm−1 at room temperature of cotton and residue -100 was analyzed using SHIMADZU (Japan)).

Figure 1. Infrared spectrum of flame retardant

Vertical fire test. Combustion conditions of raw and treated cotton fabric samples were tested in vertical position using YG815B vertical fabric FR tester according to ASTM D6413−99.

Cone calorimeter test. Combustion conditions were measured for raw cotton and processed cotton with a cone calorimeter. Specimens (100 mm × 100 mm) were tested under a radiant heat flux of 35 kW• m−2 using a cone calorimeter in a horizontal configuration according to ASTM E1354. Relevant data parameters were recorded.

Results and discussion. Structural analysis. The FT-IR spectra of the new flame retardant were determined and it is shown in Figure 1. For flame retardants, a broad peak appears near 3500−3000 cm−1, attributed to P-N and P-OH; A strong peak at 1651 cm-1 represents the deformation vibration of the N-H bond; Two similar peaks at 1446 cm-1 and 1410 cm-1 correspond to -C = O and C-N bonds, respectively; The characteristic absorption peaks of P-O appear at 1215 cm-1; and peaks at 759 cm-1 and 887 cm-1 represent P-N and P-O-C bonds. These characteristic peaks correspond to the structure of flame retardant.

Combustion process. The cone calorimeter is used to study the burning process of cotton fabrics under real burning conditions and to measure important parameters, including burning time , heat release rate , the highest or average rate of heat release was used to obtain. or average, total heat output , average effective heat output  and CO2/CO and residual ratio. THR and THR curves are shown other parameters shows that the HRR curve of raw cotton contains a significant peak at 24 seconds around 199.45 kW. /m2. This indicates that cotton raw material burns quickly after burning, releasing a large amount of heat in a very short time. The heat supports the continuous burning of the cotton fabric. In contrast, the HRR of treated cotton remained at a relatively low level of 8.99 kW/m2. In addition, the average HRR of raw cotton was 9.20 kW/m2, while that of treated cotton was only 4.83 kW/m2. 47.5% changed. These data show that cotton fabrics release heat slowly during combustion and degrade after flame retardant treatment, which helps prevent the continuation and spread of combustion. Cotton untreated with flame retardant ignited at 9 s (TTI), but treated cotton could not ignite.

After flame retardant treatment, vertical burning test and limiting oxygen index test were used to visually observe the fire resistance of cotton fabric, and the results burned inside and left a small amount of residue. In the same case, the treated cotton could not be combusted and a clear dense carbon residue was formed after combustion. For cotton fabrics treated with 15%, 20% or 25% flame retardant, the char length after ignition is 7.71, respectively; It was 6.39 and 5.52 cm.

Conclusion. In this study, highly effective flame retardants rich in P, N were synthesized and applied to cotton fabrics to increase the fire resistance of cotton fabrics. The thermal degradation and heat resistance of cotton were studied. It was proved that the cotton fabric treated with 25% flame retardant can be much more resistant to fire compared to the cotton that was not treated with flame retardant.

References

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