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High temperature resistant flame retardant protective clothing fabric

2019-01-23 08:24 | writer: admin

 
At present, the structure of the internationally-friendly high-temperature resistant flame-retardant protective clothing is mainly divided into three layers: the flame-retardant outer layer, the waterproof gas-permeable layer and the heat insulation layer. The materials used in these three layers are described below.
2.1 Flame retardant outer layer
(1) Aramid fiber. Aramid fibers are classified into isophthalic acid phenylenediamine fibers (foreign trade name Nomex, domestic trade name aramid 1313) and terephthalic acid phenylenediamine fibers (foreign trade name Kevler, The domestic product name is Aramid 1414). Nomex is currently the most widely used protective clothing material in the world. This protective clothing can effectively provide protection against the dangers caused by sudden fires, including high temperature and flame. This is because Nomex is a flame-resistant and high-temperature resistant fiber. The fire does not melt and does not support combustion; in addition, the protective power provided by Nomex protective clothing is permanent and will not be reduced by washing or wearing.
Aramid 1313 fiber is a linear macromolecule composed of aryl groups bonded to each other by an amide bridge. Due to its strong hydrogen bonding, it is structurally stable, has excellent heat resistance and excellent flame retardant properties, chemical resistance and mechanical properties. [5] Aramid 1313 fiber can maintain high temperature under normal high temperature conditions. The strength of the 177 ~ 200 ° C working temperature, the time up to 20 000 h can still maintain about 90% of the original strength. Incombustible in the flame, the LOI (oxygen index) value reaches 29~32. It is resistant to most acids, bases, bleaches and solvents with a breaking strength of 0.47 N/tex (1 tex = 10-6 kg/m). In short, aramid 1313 fiber has good comprehensive performance, long heat-resistance life, wear resistance, good resistance to multiple folds, and resistance to various chemical reagents. Therefore, it is suitable for the production of work clothes in flammable and explosive environments and materials used at high temperatures. [5].
(2) Visil fiber [6]. Visil fiber is a new type of high temperature resistant flame retardant viscose fiber made by Sateri OY of Finland. This fiber is composed of cellulose and silicate, not a simple cellulose fiber. It is a hybrid fiber produced by a two-phase natural regeneration process based on the viscose fiber production process. This fiber is mainly composed of cellulose, and its macromolecule forms a network of silicate molecules and a large amount of chemically bound water. The combination of silicate and water changes the combustion properties of cellulose, especially the use of aluminum to change the surface properties of silicic acid. During the pyrolysis process, the surface of the inorganic portion contributes to the binding of the radicals, thus retarding the combustion. It is for this reason and the release of chemical water that the combustion rate is slow, and if the fire source is removed, it has self-extinguishing ability. The release of chemical water is also an important factor in the flame retardancy of Visil fibers.
The physical and mechanical properties of Visil fiber are similar to those of ordinary viscose fiber. It is not only hygroscopic, easy to dye, but also resistant to acid, alkali and insects. Compared with other flame retardant fibers, it has low cost and no pollution, and can be processed into various textiles. This fiber can be converted into an organic and inorganic mixed soil by natural biodegradation. If carbonized under high temperature conditions, it will burn to form non-toxic SiO2. Because the molecular structure of this fiber determines the particularity of its technical performance, according to ISO 4589 "plastic - oxygen index method for the determination of flammability" standard test, its LOI is 28 ~ 31; moisture regain is 9% ~ 11%; The water absorption capacity is 50% ~ 60%; the single fiber strength is 1.5 ~ 1.9 cN / dtex; the elongation is 18% ~ 25%; the silicate content (SiO2 + Al2O3) is 30% ~ 33%.
(3) Polysulfonamide fiber (PSA) [9]. Polysulfonamide, a polysulfonamide fiber, is a high temperature resistant fiber jointly researched and produced by Shanghai Textile Research Institute and Shanghai Synthetic Fiber Research Institute, from terephthaloyl chloride and 4'4 diaminodiphenyl. Sulfone and 3'3 diaminodiphenyl sulfone are polymerized as main raw materials, dissolved in dimethylacetamide, and then processed by a wet spinning process or a dry spinning process. Its fiber-forming polymer is a linear macromolecule composed of an amide group and a sulfone group which are bonded to a para-phenyl group and a meta-phenyl group, and a strong electron-withdrawing sulfone group is present on the main chain of the macromolecule. The double bond of the benzene ring is conjugated to give it excellent heat resistance.
The mechanical properties of polysulfonamide are similar to those of aramid 1313, and its heat resistance, thermal stability and flame retardancy are superior to those of aramid 1313 fiber. In addition, it also has lubricity, abrasion resistance, impact resistance, electrical insulation and the like. Its LOI value is up to 33, and its chemical resistance is good. In hot air (300 ° C, 2 h), the shrinkage rate is <2%, and the strength retention rate (300 ° C, 100 h) is 80%.
2.2 Waterproof layer with good waterproof and moisture permeability
The waterproof layer is placed against the outer fabric to provide water resistance and to prevent the infiltration of steam and harmful chemicals. We know that a large amount of water is used as a fire extinguishing agent to fire a fire. If the fire service is not waterproof, there will be many adverse effects: 1 In the winter, firefighters wearing a wet fire service will cause frostbite; 2 wet fire The hot steam generated when the fire is close to the flame will cause burns to the firefighters; 3 excessive water absorption will increase the load, affecting flexibility and comfort. Therefore, the main purpose of the waterproof layer is to keep the firefighters dry and protect the wearer from toxic fumes and harmful chemicals. At the same time, the firefighters have a large amount of activity and sweating during the fire fighting. Therefore, the fire service must meet the requirements of waterproofing, and must also have moisture vapor permeability so that the sweat can be discharged in time. Therefore, the waterproof layer fabric is both waterproof and vapor-permeable, that is, a waterproof and moisture-permeable fabric that is impervious to moisture but permeable to water vapor.
The most famous microporous membrane waterproof and moisture permeable coated fabric is GoRE-TEx8 fabric produced by GoRE Company of USA. It is a white GORE-TEX film made by GO's patented technology. The film consists of 9 billion small holes per square centimeter. These pores are 20,000 times smaller than water molecules and 700 times larger than water vapor molecules, and are arranged irregularly. Therefore, GoRE-TEx8 fabric can not only let the human body emit sweat naturally, but also block the external rain, snow and cold wind from invading the human body. Therefore, it is called "the second layer of skin of the human body. GoRE-TEx8 fabric was introduced to the market in 1976. It can reduce the amount of moisture accumulated in the fabric and improve the comfort, especially in the harsh weather conditions to avoid obvious water vapor condensation in the garment; secondly, under certain conditions, provide the body with appropriate physiological comfort, the largest The adverse effect of the waterproof layer on the evaporation heat of sweat is reduced to a limit.
2.3 insulation layer [7]
According to the data, the temperature of the fire is between 60 and 1 100 °C, and the radiant heat is between 1.5 and 200 kW/(m2•s). Therefore, the protective clothing suitable for the fire must have good thermal protection, including direct burning. Thermal conductivity and radiant heat penetration. It is not enough to rely on a thin flame-retardant outer layer. If the thickness of the outer layer material is increased to meet the requirements, the cost will be too high. The new fire-fighting garments are generally made of permanent flame-retardant short fibers with good performance to make thin felt-like non-woven fabrics. These materials are particularly prominent for the thermal protection of fire-fighting suits as insulation materials for fire-fighting suits.
A protective suit for firefighters of the DuPont Company of the United States disclosed in the patent CN 101001547 A [14], wherein the heat insulating layer is a batt containing para-aramid or meta-aramid. Insulation is used to prevent the introduction of heat to increase the tolerance time of firefighters or high temperature workers. The insulation is often located in the innermost layer of the garment, so the comfort is also very important. Several excellent insulating materials are as follows: 100% waterproof flame retardant wool, aramid needled fabric and aramid nonwoven batt.


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