Sol-gel technology for providing flame-retardant properties of cellulose textile materials
At present, certain achievements have been achieved in the field of creating textile materials with flame retardant properties. In various countries, research is being widely carried out to increase the flame retardant properties of both natural and synthetic fibers [1–6]. Sol-gel technology is actively introduced into the production of flame retardant coatings and fibers [7–12]. Therefore, studies on the creation of flame retardant textile materials using sol-gel technology, as well as the study of their properties, have both scientific and practical significance.
The purpose of this study is to produce cellulose materials with flame retardant properties using sol-gel technology. As the main component for the preparation of sol, it is proposed to use sodium silicate, as hydrolysis catalyst – acetic acid, and it is also advisable to use chemicals that can reduce the combustibility of textiles.
METHODOLOGY OF RESEARCH
The processing of the cotton fabric of article 1030 using a sol-gel composition was carried out in two stages. First, cotton samples were impregnated in sodium silicate for 1 minute followed by wringing to a humidity of 90%, drying at 75–85°C for 8–10 minutes, then the fabric was heat treated at temperatures of 110, 130 or 150 °C for 1 minute followed by washing in a large amount of distilled water and drying. After treatment with sodium silicate, in the second stage, the samples were impregnated in a flame retardant solution for 1 minute, wringed to a humidity of 90%, dried in an oven at 75°C for 3 minutes followed by washing in distilled water and drying at room temperature.
Tests on the flame retardant efficiency of the developed compositions were carried out in accordance with GOST R 50810-95, which regulates methods for determining the ability of textile materials (fabrics, non-woven fabrics) to resist inflammation, sustainable burning, and also for assessment of their fire retardancy. The standard is applied to all combustible decorative textile materials supplied to the consumers.
The ability of the specimens to withstand tensile forces prior to rupture was determined on a tensile-testing machine with a constant lowering speed of the lower clamp PT-250M-2. The test was carried out in accordance with GOST 8847-85.
Electron microscopy of the samples was carried out using a low-vacuum scanning electron microscope JSM-6510LA.
Measurement of the flame retardant properties of cotton fabric was carried out for three heat treatment modes: 110, 130 and 150 °C. Studies of fire retardant finishing using the proposed compositions showed that the untreated cotton fabric, when tested for flammability at the ignition time of 15 seconds, completely burned in 60 seconds. For samples treated with a flame retardant composition, at the ignition time of 15 seconds, the smoldering time is close to zero. Studies have shown that increasing the concentration of fire retardant leads to a change in the properties of the tissue: with increasing concentration, the length of the charred area decreased from 220 to 98 mm (Table 1, Fig.1).
All the studied modifying compositions at optimal concentrations provide a high fireproofing effect of the tissue. A study of the change in the tensile strength of the tissue showed that the tensile strength of the control sample is 202 N, and after processing at a temperature of 150 °C it fluctuates within a small range, from 202 to 196 N (Fig.2). An increase in the concentration of fire retardant leads to a slight decrease in the strength of the tissue, and its appearance varies insignificantly. The breathability indices of cotton fabric treated with the proposed composition vary slightly and meet the regulatory requirements of hygienic safety for this group of materials (Table 1).
Electron microscopic images (Fig.3) confirm the formation of a thin polymer film on the surface of the fibers. The results of scanning electron microscopy show a change in the morphology of the surface of the treated samples compared to the untreated samples.
According to the data of scanning electron microscopy and energy dispersive microanalysis (Table 2), pure cotton fabric contains 69.95% carbon and 30.05% oxygen. After the modification, the particles of Si (6.91%), P (4.25%), S (2.26%) are formed on the surface of the treated fabric, which are distributed rather unevenly. It was shown that with increasing of the concentration of the flame retardant in the modifying composition, the content of phosphorus and sulfur in the processed samples increases to 6.16% and 3.73%, respectively.
The results of energy-dispersive microanalysis (Table 2) give an information about the quantitative content of elements in processed and untreated samples.
New compositions based on sodium silicate and flame retardant have been developed to impart flame retardant properties to cellulosic materials. Optimal conditions for tissue treatment were determined, the influence of the concentration of the working solution, the impregnation temperature, and thermal fixation on the flame retardant properties of the tissue was studied. It has been shown that cellulose materials modified with compositions based on sodium silicate and flame retardant have increased flame retardant properties. The proposed compositions provide improved fire resistance. Processing can be carried out on standard industrial equipment without the need for high-temperature fixation. ■