The use of flame retardant finishing technology for polyester fabrics
In recent years, the average number of fires that occur in my country every year is 30,000 to 40,000, with a death toll of 2 to 3,000, and fire losses equivalent to RMB 200 to 300 million, and there is an upward trend. According to surveys on fire causes in the United States, Britain, Japan and other countries, fires caused by fabrics account for half of the total number of fires. Therefore, preventing fires caused by fabrics has attracted the attention of people all over the world.
With the rapid increase in the consumption of various civil and industrial fabrics, especially the increasing demand for various interior decoration, cabin decoration fabrics and bedding, the number of fires caused by fabrics is also increasing. In the 1960s, developed countries such as Japan, Europe and the United States put forward requirements for fire-proof finishing of fabrics, and formulated fire-proof standards for various types of fabrics. my country also formulated corresponding fire-proof standards and clearly proposed test methods for fire-proof products and Technical indicators provide guarantee for the quality control of fabric fire protection. In terms of application, non-fire-retardant fabrics are restricted based on the types of fabrics and applicable places.
Because polyester fabrics are made from synthetic materials, they are particularly flammable, so the development of polyester fire-resistant fabrics is extremely important. In addition, because the polyester fire-proof fiber is limited by the amount of fire-proof materials added during the spinning process, it is difficult to achieve the ideal fire-proof effect. According to the characteristics of polyester fiber, we adopt the polyester fire retardant ATP from Beijing Jieshuang High-tech Co., Ltd. and use the padding method to embed the small molecules of the fire retardant material into the macromolecules of the polyester to form a good bond during the high-temperature setting process. , which not only shows good fire retardant effect, but also has excellent washability.
1. Fire protection mechanism of polyester fiber
There are many types of polyester fibers, and their structures are also different. Therefore, their burning conditions are also different. The burning of fabrics, like other substances, must meet three conditions: heat, air and combustibles. The burning of fabrics is caused by external heat sources. When the temperature of the heat source reaches a certain height, it decomposes or cracks to produce flammable gas, which mixes with oxygen in the air to cause it to catch fire. Among them, the physical and chemical reactions that occur in the gas phase, liquid phase and solid phase are very complex and are affected by various factors. Therefore, it is still difficult to quantitatively analyze them. Qualitative descriptions of fabric burning are also not yet complete.
The process of burning fabrics includes steps such as heating, melting, cracking and decomposition, oxidation and ignition. The speed at which each step proceeds is also affected by many factors. After the fabric is heated, physical changes such as water evaporation, softening and melting occur first, followed by chemical changes such as cracking and decomposition. Physical changes are related to the specific heat, thermal conductivity, melting heat and latent heat of evaporation of cloth fibers; chemical changes are determined by the decomposition and cracking temperature of fibers and the latent heat of decomposition. In addition, the type, tissue structure, surface shape, etc. of the fabric also have an impact on its combustion.
1. Polyester fiber fire protection mechanism
The fire resistance of materials is often achieved through mechanisms such as gas phase fire protection, condensed phase fire protection, and interrupted heat exchange fire protection. It is a gas-phase fireproofing that suppresses free radicals that promote the growth of the combustion reaction chain and plays a fireproofing function; it is a condensed-phase fireproofing that delays or blocks the thermal decomposition of polymers in the solid phase and plays a fireproofing role; it takes away part of the heat generated by polymer combustion and The fire prevention caused by this is a type of fire prevention that interrupts the heat exchange mechanism. However, both combustion and fire protection are very complex processes involving many influences and factors. It is difficult to strictly classify the fire protection mechanism of a fire protection system into a certain one. In fact, many fire protection systems work with several fire protection mechanisms at the same time.
The fireproof finishing modification method of polyester fiber fabrics is simple in process and low in cost. It is more advantageous than the raw fiber modification method in terms of the diversity of circulation and the adaptability to various fireproofing requirements. However, if the amount of fire retardant is large, it will have a greater impact on the feel and color of the fabric. There are generally three categories of methods for fireproof finishing of polyester fabrics:
1) The dissolving fire retardant agent is easy to use and has good fire retardant effect. It is suitable for fire retardant finishing of natural and chemical fiber fabrics and papers that are not resistant to cleaning. It is also suitable for fire retardant finishing of interior decoration materials used in hotels, automobiles, etc.
2) Design the fire retardant into an adsorption-type structure like disperse dyes, and adopt a finishing-coloring one-bath process. Such as fire retardant JLSUN®ATF.
3) Use hot melt method to fix the fire retardant that has great affinity with polyester on the fiber. There are not many types of fire retardants suitable for this method, they have little impact on the hand feel and have good washing fastness. Such as fire retardant JLSUN®ATP.
2. Thermal cracking of polyester fiber
Thermal cracking of fibers is a crucial step in the combustion process of fabrics. It determines the composition and proportion of cracked products and has a great bearing on whether the combustion can continue. Understanding the thermal cracking of fabrics and the products of thermal cracking can help us develop fire retardants and formulate fire-proof finishing processes for fabrics. These flammable substances can be reduced or enclosed through fire-proof finishing to achieve the purpose of fire prevention.
Polyester fiber is one of the most widely used synthetic fibers. It burns like other synthetic polymer materials. It comes into contact with high-temperature heat sources. After absorbing heat, a thermal cracking reaction occurs. The thermal cracking reaction generates flammable gases. In the presence of air (oxygen), combustion occurs, and combustion producesAfter the heat is absorbed by the fiber, it promotes the continued thermal cracking and further combustion of the fiber, forming a cycle. For synthetic fibers to continue burning, the following conditions must be met: ① The polymer decomposes and can produce flammable gas; ② The heat generated by combustion is enough to heat the polymer to continuously produce flammable gas; ③ The combustible gas generated can combine with oxygen Mix and spread to the ignited part; ④The burning part spreads to the mixed area of flammable gas and oxygen. In response to these four conditions, people have proposed the basic principles of fire prevention: reducing (or basically eliminating) the generation of thermal decomposition gases, hindering the basic reactions of gas-phase combustion, absorbing heat from the combustion area, and diluting and isolating the air.
2. Fireproof finishing process
Fire-retardant fabrics can be woven directly from fire-retardant fibers. Since this method is made by adding fire-retardant materials during the melt spinning process of synthetic fibers, it is subject to the type, physical properties and amount of the fire-retardant materials. Impact, otherwise it will directly affect the fiber fireproofing effect and the implementation of the fiber spinning process. Due to the limitation of the addition amount of fire-retardant materials (generally the addition amount is 3-%), this kind of fire-retardant fiber generally does not achieve the ideal fire-retardant effect, so this method is rarely used. The general fire retardant finishing process is to adopt the method of post-fire retardant finishing of fabrics. Depending on the characteristics of the fire retardant, the type of polyester fabric and the use of the fabric, different finishing methods are adopted.
1. Durable fireproof finishing process
Using JLSUN® ATP from Beijing Jieshuang High-Tech Co., Ltd. can reach the B2 level index of the national fire protection standard and can withstand more than 30 washes.
(1) Pre-processing process:
It is best to perform alkali reduction treatment before fire-proofing finishing to change the polyester fiber’s weak water absorption and low liquid carrying capacity, effectively remove impurities on the fabric surface, prevent the presence of other additives, and improve the fire-proofing finishing effect.
Process formula: NaOH 20-30g/l
Anionic penetrant 0.2 –0.5g/l
Processing temperature and time: 95-100℃ 20-60 minutes
The treated fabrics are washed thoroughly, the residual alkali is removed and then dried
(2) Fire prevention finishing process:
The usage amount of fire retardant ATP should be adjusted accordingly according to the thickness of the fabric.
A prescription: ATP fire retardant 90-180g/l
5-10% NaOH Adjust pH to 6-6.5
Cross-linking agents, anti-migration agents, and softeners can also be added to the process formula to further improve the effect, but compatibility experiments are required.
B chemical operation:
First add a small amount of soft water, then add the required ATP and fully dissolve it. Add 5-10% NaOH solution dropwise until the pH value of the solution reaches 6-6.5, add 80% water, then add other additives, stir, and dilute with water to the specified scale. The prepared working fluid should be used as soon as possible.
C． Process flow: Two dips and two rollings (water rolling rate 50-70%) → drying (100℃/1-2min) → baking (185-195℃/1.5-2min) → water washing → drying
Notes:
The above process formula and process will be adjusted appropriately according to the specific finishing conditions.
(a) Necessary small-scale tests should be carried out when adding other additives
(b) The baking temperature must be strictly controlled, otherwise it will affect the washability and fireproofing effect
For some unusual dyes, a small test of color change should be done before production.
2. Non-durable fireproof finishing
The non-durable fireproof finishing of polyester fabric is similar to that of cotton fabric. It is also finished with a certain concentration of borax-boric acid, ammonium polyphosphate, etc. solution. The weight gain of the finished fabric can generally meet the requirements fire protection effect. Thin polyester fabrics are more difficult to process. Usually, under the same weight gain, fabrics with greater mass per unit area have better fire protection effects, so thin fabrics often require higher weight gain rates. Thin fabrics cannot adsorb fire retardants as fully as thick fabrics. Fire retardants tend to form hoarfrost on the surface of the fabric, causing the fire retardant to seep out, affecting the appearance and feel. Therefore, the fire-proof finishing of thin polyester fabrics must take into account both the fire-proofing performance and the finishing effect of the fabric. Typical products include SCJ-968 from Beijing Jieshuang High-tech Co., Ltd.
Fire retardant agent SCJ-968 is easy to use and has good fire retardant effect. It is suitable for fire retardant finishing of natural and chemical fiber fabrics and papers. It is also suitable for fire retardant finishing of interior decoration materials used in hotels, automobiles, etc. SCJ-968 appears as a colorless and transparent liquid with a solid content of more than 20%. It is miscible with water and has a PH value of 7-8. Ideal for non-durable fire retardant finishing of cotton fabrics.
The process flow is:
(1) Spray treatment: SCJ-968 50-80% is sprayed directly onto decorative fabrics and absorptive materials such as curtains, wallpapers, sofas, carpets, etc. After drying, good fire retardant effects can be obtained.
(2) Padding method: (SCJ-968 50-80%) → drying → shaping and tentering. This method can be completed in the same bath as other finishing touches, such as soft finishing.
3. Relevant standards for fire-resistant fabrics
There are currently many international standards for fire-resistant fabrics, such as British BS, German DIN, Canadian GCSB, American FS, Swiss SNV, Japanese JIS, French ANF, Swedish SIS, Chinese GB, and international standards such as ISO. Regions and organizations in certain countries, such as major cities or states such as New York, Boston, and California in the United States, as well as the Department of Commerce (DOCFF), Transportation Department, etc.(DOT) and military agencies, etc.; various groups, societies or associations, such as the National Fire Protection Association (NFPA), Association of Fabric Chemists and Colorists (AATCC), Society for Testing and Materials (ASTM), etc., all have their own set of standards and testing methods. Different types of fabric products or finished products have different testing methods.
1. Standards for fire-resistant fabrics commonly used in my country
(1)GB8965 “Fireproof Protective Clothing”
This standard specifies the technical requirements, test methods, inspection procedures, marking, packaging, transportation and storage of fire-resistant protective clothing. It is only applicable to workers engaged in open flames, emitting sparks, operating near molten metal and flammable substances. And fire-resistant clothing to be worn in places where there is a risk of fire. The fire resistance of its clothing materials should be tested according to GB/T5455 and meet the B1 level requirements specified in GB17591.
(2) GB17591 “Fireproof woven fabrics”
This standard specifies the product classification, technical requirements, test methods, inspection rules, packaging and marking of fire-resistant woven fabrics. The standard divides the fire resistance of fire-resistant woven fabrics into two levels: 1) Level B1: damage length ≤ 150MM, afterburning time ≤ 5S, smoldering time ≤ 5S; 2) Level B2: damage length ≤ 200MM, afterburning time ≤ 15S, smoldering time ≤10S. The test method of fire resistance is in accordance with GB/T5455. The assessment level is determined according to the use of the product or through negotiation between the supply and demand parties. Generally, level B1 is suitable for clothing and highly needed decorative cloths, and level B2 is suitable for various decorative cloths.
(3)GB50222 “Code for Fire Protection Design of Internal Building Decoration”
This standard stipulates the fire protection requirements and test methods for home decoration fabrics (such as curtains, curtains, bedspreads, furniture coverings, etc.). According to the GB/T5455 vertical method, the decorative fabrics in underground civil buildings must meet the B1 level requirements, the decorative fabrics in high-rise civil buildings must meet the B1 level requirements, and the bedspreads of residences and hotels in high-rise civil buildings must meet the B1 level requirements. B1 level requirements, while curtains, curtains and furniture wrapping fabrics must also meet B1 level or B2 level requirements depending on the building and location.
2. Commonly used testing methods for fire-resistant fabrics
(1) Planar combustion method
Under the specified conditions, ignite the fabric sample in the horizontal direction for 15 seconds, measure the distance the flame spreads on the sample and the time it takes to spread the distance, and measure it by the measured flame spread time and flame spread rate. The fire-retardant effect of fabrics.
(2) Vertical combustion method
The vertical burning method refers to using a specific ignition source (flame height 40mm±2mm) to burn the vertical fabric fixed in a U-shaped clip at the center 20mm from the bottom edge of the fabric. Pass the assessment within the prescribed burning time. It is a method to test the fire resistance of fabrics based on indicators such as the burning state of the fabric, afterburning time, smoldering time, and damage length. my country and most countries mostly use the vertical burning method to test the fire resistance of fabrics. Japan uses it to test the fire resistance of workwear fabrics, and the United States, the United Kingdom and Germany use it to test the fire resistance of children’s underwear, protective clothing, and decorative fabrics. . The vertical combustion method is one of the most complete fire protection performance testing methods at home and abroad. Most standards have played a role in regulating and guiding in various industries, such as my country’s GB8965 98 “Fire Resistant Protective Clothing” GB17591 1996 “Fire Resistant Woven Fabrics” , GB50222 95 “Code for fire protection design of building interior decoration”, HB5470 96 “Combustion performance requirements of non-metallic materials in civil aircraft cabins”, GB8410-87 “Automotive interior decoration materials”, Japan’s JISD1201 FMVSS302 “Automotive decorative fabrics”, TCL1008 69 ” Aircraft Decorative Fabrics”, American NFPA701 “Curtain Fire Resistance Performance”, etc.
(3) 45° inclined plane combustion method
Under the specified conditions, place the sample at an angle of 45°, ignite the sample for 1 second, and use the time required for the sample to burn upward for a certain distance as a method to evaluate the severity of fabric burning. Afterburning and smoldering time, damage area and damage length are used to measure the fire protection effect of fabrics.
(4) Limiting oxygen index (LOI) method
The oxygen-limiting index method refers to the low oxygen concentration required to maintain candle-like burning of the fabric when the fabric burns in a mixture of oxygen and nitrogen. The greater the oxygen-limiting index, the better the fire protection effect of the product, and vice versa. The worse the effect or the less fireproof. Although the oxygen-limiting index method has the advantage of high sensitivity, it has high requirements on test conditions and operators, and the oxygen concentration in the test is quite different from the actual use conditions of the fabric. Therefore, the oxygen-limiting index method is particularly suitable as a test in scientific research. means and are not often used in the product production process.
The test of fireproof performance is a particularly important link in the research on fireproof finishing. There are two commonly used fabric fire resistance testing methods: vertical burning method and oxygen index method. The vertical combustion method has a detailed definition and specification in the national standard GB5455-85. Generally speaking, the oxygen index method is more suitable for horizontal comparison of the fire resistance of samples of the same material and fabric structure. The limiting oxygen index (LOI) value alone is not enough to explain the fire resistance of the sample; the damaged char length measured by the vertical combustion method can objectively describe the fire resistance of the fabric. However, compared with the vertical combustion method, the data measured by the oxygen index method are accurate and have good reproducibility. Therefore, the oxygen index method is more suitable for process experiments; the vertical combustion method can evaluate the final fire resistance of fabrics.
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