ABSTRACT

A new halogen-free flame retardant was prepared and impregnated on cotton fabrics. IRTracer-100 SHIMADZU IR-Fourier spectrometer was used for the structure of phosphorus and nitrogen compounds in the system. The results of ATR-FTIR spectroscopy analysis showed that the flame retardant cotton surface was successfully coated. We investigated the thermal stability and fire behavior of cotton fabrics using a vertical flame test. We also studied the fire resistance mechanism of coated cotton fabrics.

АННОТАЦИЯ

Приготовлен новый безгалогенный антипирен для хлопчатобумажных тканей. Для определения строения соединений фосфора и азота в системе использовали ИК-Фурье-спектрометр IRTracer-100 SHIMADZU. Результаты анализа спектроскопии ATR-FTIR показали, что огнестойкая хлопковая поверхность была успешно покрыта. Мы исследовали термостойкость и огнестойкость хлопчатобумажных тканей с помощью испытания на вертикальное пламя. Мы также исследовали механизм огнестойкости хлопчатобумажных тканей с покрытием.

Keywords: phosphoric acid; pentaerythritol; fire resistant; cotton fabrics; ammophos

Ключевые слова: фосфорная кислота; пентаэритрит; огнеустойчивый; хлопчатобумажные ткани; аммофос.

Introduction. Cotton fabrics are recognized as one of the most important natural fibers available in apparel, home furnishing and industrial applications. This is due to the excellent properties of cotton, such as biodegradability, softness, warmth and recyclability[6]. However, attention is paid to the high flammability of cotton fabrics in cotton production[2]. An appropriate flame retardant (flame retardant) should be used to slow the burning of cotton fabrics and/or reduce the spread of fire [7] Among the various technological methods developed by academics to prepare cotton fabrics with durable flame retardant coating, flame retardant coatings have become one of the most convenient, economical and effective methods [1]. Cotton fabrics are often treated with a reactive flame retardant or recoated to improve their flame resistance. For example, silicones[4] polyurethanes[3], and polyphosphonates (PEPBP) oated on cotton surfaces are used to provide adequate flame retention under adverse environmental conditions. In addition to polymer matrix-based flame retardants, various active flame retardants have been proposed to impart flame resistance to cotton fabrics[5]. The above flame retardant compounds may also contain phosphorus elements or combinations of P and N elements for synergistic interaction. A cross-linked organophosphorus flame retardant system was incorporated into cotton fabrics. Oligomeric OH-terminated methylphosphonate-phosphate cellulose from cotton or cotton/nylon blends treated with commercial flame retardants showed higher carbon residues due to the catalytic effect of phosphoric acid on cotton/nylon fabrics to dehydrate cellulose.

Flame retardant is introduced into the substrate by UV irradiation or soaking. a chemical cross-linking reaction took place between the flame retardant and the cotton matrix, and excellent thermal stability was found under high temperature conditions. It also showed that flame retardant treated cotton had a higher initial degradation temperature and more charring compared to virgin cotton. In this study, a new flame retardant formulation was synthesized using pentaerythritol and ammophos. The structure of the formula was characterized using FTIR analysis. The surface and thermal behavior of purified cotton was characterized using ATR-FTIR analysis. In addition, we proposed a mechanism for obtaining phosphorus and nitrogen flame retardants in cotton fabrics by studying the chemical structure and elemental composition of coal residues.

Experimental part

Materials. Cotton fabrics: 100% cleaned and bleached plain weave cotton fabrics with a density of 237 g/m2, ammophos, urea, pentaerythritol, urea.

Preparation of flame retardant based on pentaerythritol and ammophos

Flame retardant containing phosphorus and nitrogen was synthesized by the reaction shown in scheme 1. Pentaerythritol, ammophos and urea were taken in a mass ratio of 1:2:4 and placed in a 500 ml beaker and reacted in a magnetic stirrer for 4 hours at 200-2500C. After the reaction continued for 4 hours, a brown viscous substance was formed. ammonia and water vapors escaped from the mixture. Pentaerythritol polyphosphate (ammonium salt) was formed as a reaction product 

Scheme 1. Synthesis reaction scheme of the flame retardant system containing little phosphorus and nitrogen

Fabric processing. For illumination, we used a lamp with a wide-band UV-source (made in China). Empty cotton fabrics are immersed in an acetone solution containing a flame retardant system at room temperature in a 1% nitrogen and phosphorus flame retardant solution, and then neutralized with an ammonia solution to pH 7-8. Finally, after ten washes, each sample was dried at room temperature (30 ◦C) until no weight loss was detected..

FTIR spectroscopy .We used the IRTracer-100 SHIMADZU brand IR-Fourier spectrometer (Japan) (range 400-4000 cm-1) to determine functional groups and bonds in the obtained samples.

Vertical flame test. The vertical flame test was performed according to the DIN 53906 standard method [2]. The sample size was 120 mm × 60 mm. Butane gas was chosen for combustion. The flame height and burning time were about 40 mm and 10 s, respectively. The average burning time (post-fire and pre-fire) of five test samples was recorded.

Results and Discussion. A new flame retardant formulation was prepared using the reaction shown in Scheme 1. Figure 1 shows the IR spectrum of phosphorus-containing formulations. And a broad peak appears near 3196 cm−1, which belongs to P-OH. ); The peak at 2883 cm-1 represents the deformation vibration of the -CH2 bond, and the strong peak at 1660 cm-1 represents the deformation vibration of the N-H bond; 1454 cm−1 and 1346 cm−1 correspond to -C = O and C-N bonds, respectively [13]; The characteristic absorption peaks of P-O appear at 1252 cm-1 ; and peaks at 771 cm-1 and 1082 cm-1 represent P-N and P-O=C bonds . These characteristic peaks correspond to the structure of flame retardant.

Figure 1. IR spectrum of flame retardant containing phosphorus and nitrogen

Determination of fire resistance of cotton fabric. We investigated the flame retardancy of treated cotton fabrics using a vertical flame test. Following DIN 53906, we recorded the average post-ignition and ignition times of each of the five test specimens. Flammability results of cotton fabrics and images obtained after vertical burning tests are shown in Table 1. Refined cotton fabrics burn naturally and are almost completely destroyed without leaving any carbon residue. The PM(cotton fabric) sample burned strongly after ignition and burning times of 18 and 14 hours, respectively. In contrast, non-FR PM-A fabrics containing phosphorus behaved as highly flammable fabrics and no char residues were obtained after combustion. However, during the combustion of PM-A, a very fine and light coal was formed. This showed that the decomposition of nitrogen- and phosphorus-containing flame retardants produces ammonia gas and carboxylic acid groups during ignition. These carboxylic acid groups accelerated the dehydration of cotton fabrics.

Table 1.

Test residue and vertical flame test results of pure cotton and treated cotton fabrics

Conclusions. A new flame retardant formulation based on pentaerythritol and ammophos was successfully synthesized using a simple process. The exact structure of the flame retardant was also determined by IR spectroscopy analysis. The results of ATR-FTIR studies showed that the monomer of the flame retardant system was coated on the surface of cotton fabrics. Flame retardants contributed to the formation of thermally stable coal. Thick carbon fibers containing the same distribution of P and N elements were obtained from flame retardant coated cotton samples. The thermal stability of cotton fabrics coated with flame retardant has increased significantly. The FA system used as a durable flame retardant showed high efficiency of the condensed phase for cotton fabrics. We observed that the system exceeded the DIN 53906 standard with an additional 25%.

Referenses:

1. Ding H. [и др.]. Synthesis of a novel phosphorus and nitrogen-containing bio-based polyols and its application in flame retardant polyurethane sealant // Polymer Degradation and Stability. 2016. (124).
2. Gaan S. [и др.]. Flame retardant functional textiles 2011.
3. Giraud S. [и др.]. Flame behavior of cotton coated with polyurethane containing microencapsulated flame retardant agent // Journal of Industrial Textiles. 2001. № 1 (31).
4. Plácido J., Capareda S. Production of silicon compounds and fulvic acids from cotton wastes biochar using chemical depolymerization // Industrial Crops and Products. 2015. (67).
5. Przybylak M. [и др.]. Multifunctional, strongly hydrophobic and flame-retarded cotton fabrics modified with flame retardant agents and silicon compounds // Polymer Degradation and Stability. 2016. (128).
6. Wakelyn P. J., May O. L., Menchey E. K. Cotton and Biotechnology 2004.
7. Xing W. [и др.]. Flame retardancy and thermal degradation of cotton textiles based on UV-curable flame retardant coatings // Thermochimica Acta. 2011. № 1–2 (513).