Research on flame retardancy of linen and jute fabrics
Hemp fiber has the characteristics of fast moisture absorption and dispersion, strong tensile strength, good luster, good insulation, acid and alkali resistance, corrosion resistance, etc. It has good health care properties and is breathable, smooth, rough, bold, natural texture, Soft tones, crisp and generous, and other unique styles. At home and abroad, hemp products are widely used in work clothes, decoration and other fields. At present, the demand for linen products in developed countries is increasing day by day. One of the main uses is for room decoration, such as tablecloths, sofa cloths, wall coverings, curtains and bedding. From the perspective of room safety and fire prevention, the fire prevention finishing of hemp products has become increasingly important and has attracted much attention from fabric engineering and technical personnel [1]. This article mainly discusses the fireproof finishing of linen fabrics and jute fabrics to determine the best processes and technologies.
1 Fire prevention mechanism
Three conditions must be present to cause combustion: combustible substances, fire sources and oxygen. The essence of the combustion process is the process of solid phase decomposition to gas phase oxidation [2]. The combustion cycle is shown in Figure 1.
As can be seen from Figure 1, after combustibles come into contact with a fire source, they first undergo thermal decomposition (solid-phase decomposition), producing flammable gases, and then burn (gas-phase oxidation) under the action of oxygen. Gas-phase oxidation generates a large amount of heat. This heat is used as a supplement to the heat source to promote solid phase decomposition, thus forming a combustion cycle. It is not difficult to understand that cutting off this cycle, inhibiting solid phase decomposition (reducing the production of flammable gases) or inhibiting gas phase combustion (weakening the thermal energy level of flammable gases) can have a fire prevention effect. Flax and jute fibers belong to the category of cellulose fibers. The structure and chemical composition of cellulose fibers and lignin fibers have a great influence on their thermal properties. After the fiber is treated with fireproofing, its initial pyrolysis temperature is reduced, and even its pyrolysis termination temperature is lower than the initial pyrolysis temperature of the non-fireproof fiber, but the weight of the residue increases. This is because the presence of the fire retardant changes the pyrolysis The mechanism is: the fiber treated with fireproofing begins to dehydrate and carbonize at around 300℃, and the generation of L-glucose is inhibited when the 1,4 glycoside bonds of cellulose are broken above 340℃. Because the β-glucose 1,4 glycoside bond is broken, the intermediate product is experimentally studied to generate levoglucose or 1,6 dehydrated β-D glucofuranose. After generating levoglucose, various flammable gases are easily generated.
After the fiber is treated with a phosphorus-containing fire retardant, the initial cracking temperature of the fiber is lowered. The phosphorus-containing fire retardant can decompose at a lower temperature to generate phosphoric acid, which turns into metaphosphoric acid as the temperature increases. It is then condensed into polymetaphosphoric acid, which is a strong dehydrating agent, promotes carbonization of cellulose, inhibits the generation of flammable pyrolysis products, and thus plays a fire prevention role. In addition, the phosphoric acid produced by decomposition will form a non-volatile protective layer, which can not only isolate the air, but also act as a catalyst for oxidizing carbon into carbon monoxide during the combustion of cellulose, thereby reducing the generation of carbon dioxide. Since the heat of generation of carbon monoxide (110·4kJ/mol) is smaller than the heat of generation of carbon dioxide (394·6kJ/mol), this effectively inhibits the release of heat and blocks the burning of cellulose. Therefore, its fire prevention effect mainly occurs in the solidified phase part [3].
2 Materials and experiments
2·1 Materials and Instruments
Fabric: scoured and bleached linen fabric, jute fabric; Medicines: fire retardant, 062 resin, JFC penetrant, phosphoric acid, magnesium chloride, fat soap; Instruments and equipment: 702-2 electric heating blast box, constant temperature water bath, Small rolling mill, YG815 vertical fabric combustion performance tester, YG065 electronic fabric strength tester, LLY-01B computer controlled stiffness tester.
2·2 Experimental methods
2·2·1 Sample weighing
The sample is placed in a room with a temperature of (21±1)℃ and a relative humidity of (65±2)% for more than 8 hours. The weight of the blank sample per square meter before fire protection treatment is weighed (accurate to 0·1g) .
2·2·2 Permanent fireproof finishing process
Fabric→Padding (padding rate 75%~80%)→Drying (105℃, 5min)→Baking (155℃, 4min, 160℃, 3min, 170℃, 1·45min)→Soaping (Soap powder 3g/L, 60℃, 3min) → Dry.
2·2·3 Fire prevention effect measurement
Measure all fabrics after fireproofing. According to the provisions of GB5455-97, the vertical burning test method is adopted to measure the fabric’s resistance to afterburning, smoldering resistance and char length (large length that is charred). After vertical burning Measure on the tester.
2·3 Experimental results and discussions
The fire-proof finishing experiment of linen fabrics adopts the orthogonal design method [4] L9 (34) orthogonal table, see Table 2. Figure 2 reflects the law of changes in process indicators with various influencing factors. The range and variance analysis are shown in Table 3.
Conduct stiffness and tensile tests on the fireproof linen fabrics, and perform variance analysis on the results as shown in Table 4. The jute fabric adopts the L4(23) orthogonal table. The experimental factor levels, experimental arrangements and results are shown in Table 5. The range and variance analysis are shown in Table 6. Conduct stiffness and tensile tests on the fireproof jute fabric, and perform variance analysis on the test results. The analysis results are shown in Table 7.
3 Conclusion
1·The factor that has the greatest impact on the fire-proof finishing of linen fabrics is baking temperature, followed by resin concentration, fire retardant agent concentration and liquid padding rate. The optimal process is A3B1C1D1, that is, the concentration of fire retardant agent is 350g/L, and the resin concentration is It is 40g/L, the baking temperature is 155℃, 4min, and the liquid squeeze rate is 75%.
2·When a=0·25 for each level of each factor, the resin concentration and baking temperature have a significant impact, but below a=0·1, the effects of each factor and each level are considered to be equal, that is, fire preventionThe influencing factors of agent concentration, resin concentration and baking temperature tend to be consistent.
3·Fire retardant agent concentration, resin concentration and liquid mangle rate have a significant impact on the bending length of linen fabric after fire retardant finishing. The effects of fire retardant concentration, baking temperature and liquid rolling rate on the fracture strength tend to be consistent.
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