1. The Meaning of Flame Retardant Fabric Finishing
With the progress of society and the improvement of people’s living standards, the demand for all kinds of fabrics is not only large in quantity and variety, but also high in quality. However, fires caused by textiles are also increasing. Causing serious losses of people’s lives and properties. Especially in the past ten years, high-rise residential buildings and hotels have been built in China, and the flame-retardant requirements of interior decoration products have become higher and higher. Therefore, textiles have been improved. The flame-retardant performance of the textile has extremely important practical significance for ensuring safety and reducing the occurrence of fire accidents. Fabric fireproof is more important in nowadays.
Common textile fibers are all organic polymers, which will be cracked at 300℃. Part of the generated gas is mixed with air to form flammable gas. This mixed flammable gas will burn when it encounters an open flame.
With the large number of applications of synthetic fibers, if you accidentally catch fire, because general synthetic fibers are flammable and easy to melt, the melt viscous liquid or droplets produced will quickly adhere to human skin and cause deep burns. So people are paying more and more attention on flame retardant finishing of fabric fireproof.
In order to reduce fire accidents and avoid unnecessary losses, the following measures can generally be taken:
(1) Formulate local regulations or national laws to deal with buildings and interior decorations that are prone to fire and cause fires, including carpets, curtains, bedspreads, etc. Textiles must have flame-retardant measures to avoid or reduce fire accidents. All non-metallic materials on airplanes, automobiles, ships and trains, including a large number of imitation products, must be flame-retardant finishing to avoid or reduce fires and casualties. There are also regulations for some clothing and cloth for labor insurance.
(2) Study the flame retardant test methods of textiles. For flame retardant finished textiles fabric fireproof procedure, it is required to pass the test to evaluate the flame retardant effect. At the same time, it requires the establishment of flame-retardant standards, and certain fabrics that do not meet the flame-retardant requirements cannot be sold and used by law.
(3) The combustion performance of various textile materials must be studied, especially in recent years, chemical fibers have developed rapidly. Many of these chemical fiber fabrics are easy to catch fire, and they lack mature experience in flame retardant finishing, and some chemical fiber flame retardant finishing Later, combustion smoke is more toxic, so systematic research is needed to ensure human safety.
(4) Research and search for ideal flame retardants not only have excellent flame retardant effects, but also require low cost, good washing resistance, soft hand feel, non-toxic, and comfortable to wear.
(5) On the current basis, in-depth study of flame retardant mechanism, in order to continue to improve the level of flame retardant finishing of fabric fireproof, to solve the current problems.
2. Flame-Retardant Finishing Requirements
2.1 Requirements for Flame-Retardant Products
(1) Fire retardant fabric should have good flame-retardant properties (quality indicators: limiting oxygen index, carbonization length, after burn and smoldering, etc.).
(2) Fire retardant fabric should have good durability (washing resistance, dry cleaning resistance, weather resistance).
(3) Fire retardant fabric does not affect the feel after finishing (stickiness, roughness, stiffness, etc.).
(4) The fabric strength decreases less.
(5) There should be no defects such as uneven finishing and discoloration of water droplets on the fabric.
(6) Fire retardant fabric is odorless when in use, and will not damage or rust the contact materials.
(7) The dyed fabric will not be discolored or faded, and has no effect on the color fastness.
(8) No yellowing phenomenon occurs.
(9) No toxicity, no irritation or effect on the skin.
(10) The smoke produced after burning is non-toxic. (1) The price is reasonable, and the cost increase is not much.
2.2 Flame Retardant Process Requirements
There are two ways of flame retardant finishing. One is the additive type, that is, the flame retardant is mixed with the spinning dope, or the flame retardant is added to the polymer and then spun, so that the spun yarn has flame retardant properties. The other is the post-finishing type, that is, flame-retardant finishing on the fiber or fabric. For products, in order to meet actual use requirements, sometimes it is not enough to rely on one method alone. Some flame retardant products must also rely on flame retardant fiber blending to solve the problem. The requirements for the flame retardant finishing process are as follows:
(1) Choose a flame retardant with excellent effect.
(2) In the existing fabric dyeing and finishing equipment, no special equipment or special equipment is needed to carry out flame-retardant finishing.
(3) No effect on dyeing and auxiliaries.
(4) No environmental pollution.
The flame-retardant finishing fabric fireproof process generally has the following methods, namely, padding method, dipping and drying method, organic solvent method, coating method and spray method. The flame retardant finishing process can be selected according to the different requirements of the product. At present, it is still relatively difficult for flame-retardant finishing products to meet the above requirements. For example, in terms of the durability of flame-retardant fabrics, currently only cotton fiber is better, and other fibers need to be continuously improved and improved. Moreover, after the fire-retardant finishing of cotton fiber, the hand feel and strength will also have a certain impact. Softeners must be added to improve its performance, and the cost will increase a lot.
3. Flame-Retardant Products and Uses
As for flame-retardant products, new varieties are being developed at home and abroad. There is fierce competition in the international market, and they are generally used for clothing, decoration and industrial use. Mainly wear work clothes, pajamas and shirts for adults and children. Decorative fabrics include textiles used in airplanes, trains, automobiles and ships, as well as decorative fabrics in hotels, high-rise buildings and some public places. Home furnishing fabrics such as curtains, door curtains, tablecloths, mattress sheets, sofa covers, carpets and wall coverings. Industrial fabrics such as tent fabrics. These flame-retardant products and their fabric fiber varieties, the most used cotton fiber viscose fiber, wool is also a lot, there are some polyester, nylon or polyester-cotton blends, and there are also flame-retardant fibers woven. The types of fabrics are divided into knitted fabrics and non-woven fabrics.
The flame-retardant products must be determined according to their use. Different products require different flame-retardant properties. Generally speaking, flame-retardant products have their own specific test methods and standards. In addition to the necessary indicators, they also have certain requirements for some auxiliary indicators. These indicators can be determined according to the use of the product. For example, flame-retardant products such as clothing, bed sheets, etc. require breathability, tablecloths, tent cloths, and wall coverings, which do not necessarily require air-conditioning. There is a big difference between the choice of flame retardant and flame retardant technology. Another example is the flame-retardant products used in clothing must feel soft and comfortable, but wall coverings do not need this indicator, and the two processes are also different. Compared with the two flame retardant products of limited installation and wall covering, the former has much higher requirements for flame retardant performance than the latter. Therefore, when selecting flame retardants and corresponding processes, the procedures are more complicated and the cost will be higher.
4. The Combustion Process of Textiles
4.1 The Combustion Process
The combustion process of textiles includes the steps of heating, melting, cracking and decomposition, oxidation and ignition. After textiles are heated, there are first physical changes such as water evaporation, softening and melting, followed by chemical changes such as cracking and decomposition: heat conduction-endothermic-cracking or decomposition-air mixing-combustion and spreading-discharge.
The physical changes of textiles after burning are related to the specific heat capacity, thermal conductivity, heat of fusion and evaporation potential of textile fibers; the chemical changes are determined by the decomposition and pyrolysis temperature of the fiber, and the size of the latent heat of decomposition.
When the combustible gas generated by cracking and decomposition is mixed with air to reach a combustible concentration, it can catch fire. The resulting combustion heat increases the temperature of the gas, liquid and solid phases, and the combustion continues to be maintained. The main factors affecting this stage are the diffusion rate of combustible gas and oxygen in the air and the combustion heat of fibers. To prevent the combustion from spreading to the neighboring parts, the heat lost during the combustion process must not affect the neighboring textiles. Figure 7-3 is a schematic diagram of the textile burning process.
4.2 Commonly Used Basic Terms
The basic terms commonly used in the combustion and flame retardant process of textiles are as follows:
(1) Combustion: When combustible substances come into contact with a fire source, the oxidative exothermic reaction is produced, accompanied by a flame or flameless burning process or smoke.
(2) Burning: When the combustible substance contacts the fire source, the solid phase state of the flameless burning process is accompanied by the phenomenon of luminescence in the combustion zone.
(3) After burning: After the burning substance leaves the fire source, there is still continuous Flame burning.
(4) Smoldering: After the burning material leaves the fire source, there is still continuous flameless combustion.
(5) Spontaneous combustion: The material burns spontaneously in the air.
(6) Self-extinguishing: Under the established experimental conditions, the material stops burning after the fire source is removed.
(7) Flaming combustion: the gas phase combustion phenomenon accompanied by luminescence.
(8) Smoke: The finely dispersed particles of liquid, solid and carbon particles in the air generated by incomplete combustion of materials, which form opacity due to scattering and absorption of visible light.
(9) Smoke burning: a slow burning phenomenon in which no light is visible, usually with smoke.
(10) Ignition temperature: The lowest temperature at which the material starts to burn continuously under the specified experimental conditions, usually called the ignition point.
(11) Pyrolysis: The irreversible chemical decomposition of materials at high temperatures without oxidation.
(12) Melt drop: material droplets that melt at high temperature.
(13) Carbonization: The process of forming carbon residues during the pyrolysis or incomplete combustion of materials.
(14) Flame-retardant: The property of a certain material to prevent, slow down or stop flaming combustion.
(15) Flame spread: the expansion process of the flame front.
(16) Damaged length: The maximum length of the damaged area of the material in the specified direction under the specified experimental conditions, usually also called the carbon length.
(17) Limit oxygen index: The lowest concentration of oxygen in the nitrogen-oxygen mixed gas under the specified experimental conditions to keep the material in the burning state.
(18) Concord effect: the flame retardant ability of several flame retardant compounds when used in combination is greater than the sum of the flame retardant effects when used alone.
(19) Destructive effect: the flame-retardant ability of several flame-retardant compounds when used in combination is smaller than the sum of their flame-retardant effects when used alone.
(20) Vertical, horizontal, 45° angle (experiment): Under the specified experimental conditions, the direction of the sample during the combustion experiment.
4.3 Thermal Cracking of Textiles
In the combustion of textiles, thermal cracking is a crucial step. It determines the composition and proportion of the cracked products, which has a great impact on whether the combustion can continue, and determines the combustibility of the fiber.
Fibers can be divided into two categories due to their different effects on heat. One is thermoplastic fibers and the other is non-thermoplastic fibers.
Thermoplastic fiber: Tg, Tm<Tp, Tc
Non-thermoplastic fiber: Tg, Tm>Tp, Tc
Among them: Tg is the glass transition temperature; Tm is the melting temperature; Tp is the thermal cracking temperature; Tc is the combustion temperature.
Non-thermoplastic fibers will not soften, shrink and melt during the heating process, and the combustible gas produced by its thermal cracking will be mixed with air and burned to generate char. Such fibers include various natural fibers, flame-retardant fibers and high-temperature resistant fibers. In the heating process, thermoplastic fibers will soften when the temperature exceeds T, and when they reach Tm, they will melt and become viscous rubber. When burning, the melt is easy to drip, causing difficulty in continued burning, but the high temperature melt will stick to the skin and cause deep burns. Such fibers include synthetic fibers such as polyester and nylon.
The blended fabric of polyester and cotton fiber, because it has the appearance of cotton fabric, but also has the non-iron and abrasion resistance of polyester, so it is currently deeply favored by consumers. But its combustion properties are more intense and harmful than the combustibility of pure textiles. Cotton fiber begins to decompose when heated to 350°C; while polyester fiber does not decompose until 420~47°C. When cotton fiber is heated, it is easy to produce combustible pyrolysis gas. If there is enough oxygen, it will catch fire. Because of its thermoplasticity, polyester will shrink first before the pyrolysis of the cotton component, and then begin to melt. After the pure polyester fabric shrinks due to heat, it is likely to break away from the heat source that causes the combustion, and then further melt into droplets, which transfer energy from the fabric, thereby producing a self-extinguishing effect. But after polyester and cotton fibers are blended, the situation is completely different. The molten polyester component will coat the surface of the pyrolyzed cotton fiber, and the coke of the cotton will also prevent the shrinkage of the fabric. In fact, the fibrous coke not only supports the molten polyester, but also wicks the molten body into the fire source, increasing the fuel supply in the fire zone. This kind of situation can be called the “arrangement” effect. Due to this scaffolding effect, the combustibility of polyester-cotton blended fabric is much stronger than people expected; the combustibility of polyester-cotton blended fabrics with different mixing ratios is not equal to the addition of the combustibility of each fiber component. This has been pointed out by Tesoro et al. The heat dissipation rate of polyester-cotton blended fabric is proportional to its cotton fiber content, while the burning rate is controlled by polyester. This is because the polyester is first melted before burning and coated on the cotton fiber, thereby preventing the high temperature decomposition of the cotton fiber until the polyester is burned.
The reason why the oxygen-limiting index of polyester-cotton blended fabric is lower than most people would expect is that in addition to the above-mentioned scaffolding effect, it may also be due to the mutual influence of the two fibers during the combustion process. Miller et al. provided signs of mutual chemical reactions, so the blended fabric is easier to ignite than the expected components, burns more intensely, thermally decomposes faster, and produces more flammable gases. But some people think that these situations are mainly due to mutual physical interaction.
4.4 The Hazards of Burning
The burning hazards of textiles mainly include three aspects: ignitability, flame spreading and burning destructiveness. These three aspects will produce smoke and combustion gases, all of which have certain toxicity.
During the combustion process, the reduction of visibility depends on the size and composition of smoke particles, the size and shape of the sample, temperature, humidity and ventilation conditions. Combustion smoke density is closely related to combustion rate, and is inversely proportional to ventilation conditions.
To fully understand the hazards of toxic substances in the combustion process, some small molecular substances produced by the combustion of different polymers and fiber materials. Among them, carbon monoxide is the main cause of death in the fire. CO reacts with hemoglobin Hb to produce carbonylated hemoglobin Hb-CO:
This is a reversible reaction, but the positive reaction rate is 20 times that of the reverse reaction. Oxygen content is reduced), so that the oxygen pressure in the arteries decreases and the blood flow rate slows down.
100mg/L CO will produce 10%~15% carbonylation such as red protein, causing mild poisoning characterized by dizziness. 100c0 will cause severe poisoning. When the concentration of CO0 is 100g, it will cause death for 1-3min, which is equivalent to 60% of hemoglobin converted into carbonyl derivatives.
5. Flame-Retardant/Fabric Fireproof Mechanism
With the development of the production practice of flame retardant systems and effective flame retardant performance test methods, the research on the flame retardant mechanism has been promoted accordingly. A lot of discussions have been made on the role of flame retardants, and many related articles have been published. In addition to considering the chemical composition of the fiber, it is also necessary to choose the best flame retardant to prevent the fabric from decomposing and releasing flammable gases under the action of heat. There have been various theories to explain the role of flame retardants:
(1) Endothermic reaction: the flame retardant and fiber decompose at the same temperature during the heating process, and the flame retardant absorbs the heat generated during the combustion process.
(2) Generation of non-combustible gas: the flame retardant releases non-combustible gas during the pyrolysis process to prevent or dilute the contact of oxygen on the surface of the fiber with the flame.
(3) Melting theory: Under the action of heat and energy, the flame retardant transforms into a molten state, forming an impermeable covering layer on the surface of the fabric, making it difficult for air to contact the fiber surface, and preventing the release of flammable gas from the surface.
(4) The formation of free radicals: the flame retardant absorbs heat and transforms into a gas, which can capture the more active free radicals in the combustion process, thus reducing the heat released during the combustion process.
(5) Dehydration theory: Taking cellulose fiber as an example, the flame retardant causes the cellulose to undergo a dehydration reaction, which inhibits the pyrolysis reaction to a certain extent.
6. Flame Retardant System of Textile Materials
The flame-retardant processes of textile materials are diverse and developed with the development of new fibers and fabrics and flame retardants suitable for various polymers and textiles. Currently commonly used flame retardant systems are shown in Table 7-7. According to the interaction between flame retardants and polymers, they can be divided into three major types.
6.1 Non-Reactive System Surface
In a non-reactive system, no chemical reaction occurs between the flame retardant and the fiber. In most cases, only physical-chemical interaction occurs. For example: adhere to the fiber surface, or penetrate into the fiber structure, to produce adhesion to the microfibril. The van der Waals force can also be used to generate intermolecular binding force in the low side sequence region of the fiber. It can be used for finishing textile products (woven fabrics, knitted fabrics or non-woven fabrics), and can also be added to polymers before fiber formation, or used before textile processing.
Finishing agents and additives are usually external application materials. Because the concentration of textile materials is as high as 10%-30%, it may change the performance and characteristics of textile materials.
6.2 Reactive System
The flame-retardant treatment is carried out after the fiber is formed or fabricated and dyed.
Chemical and physical-chemical reactions occurred during the flame-retardant finishing process. In many cases, rolling, baking, baking or other finishing processes are used. Therefore, severe treatment conditions are required, such as elevated temperature or high-temperature radiation treatment. However, during baking, side reactions may occur, causing fiber degradation, oxidation, hydrolysis, and even thermal damage (slight thermal decomposition), and sometimes even have a significant impact on the properties of the fabric.
Active flame retardants can improve durability, for example, after more than 50 times of washing, the flame retardant properties of the finished product will not change significantly.
6.3 The Flame-Retardant Fiber
Copolymerized with a certain proportion of the main monomer and the main raw material monomer to form a new polymer, which is then transformed into a fiber, resulting in a new fiber morphology structure with different crystallinity and orientation. Density and glass transition temperature, which also changed its textile processing conditions and physical and mechanical properties.
On the other hand, special monomers can be used to polymerize to produce new polymers, which are then drawn into fibers. The new processing technology needs to consider the chemical properties of monomers and the differences between these new materials and traditional fiber products.
7. Flame Retardant//Fabric Fireproof Finishing of Common Fibers
7.1 Flame Retardant/Fabric Fireproof Finishing of Cotton Fabric
7.1.1 Temporary Flame-Retardant Finishing
This method uses a temporary flame-retardant finishing agent solution or emulsion to simply treat the fabric. The fabric can be dried by padding. There is also a two-bath padding method. About 68 kinds of flame retardants in the international market are temporary flame retardant finishing agents. Temporary flame retardant finishing agents can be divided into the following categories.
(1) Aluminum compounds: aluminum chloride, tin oxide and chlorinated paraffin; sodium ammonium aluminate and ammonium bicarbonate; aluminum phosphate or aluminum pyrophosphate; aluminum sulfate, calcium chloride and polyvinyl acetate. Product
(2) Ammonium salts: ammonium sulfate and boric acid; ammonium borate, boric acid; ammonium sulfate, borax and boric acid; ammonium sulfate, ammonium silicate, boric acid and borax; ammonium sulfamate, ammonium phosphate and urea formaldehyde.
(3) Antimony salt: antimony chloride or antimony oxide and polyvinyl chloride; antimony oxide, titanium oxide and polyvinyl chloride; antimony chloride, titanium chloride and ammonia; antimony silicate and polyvinyl chloride.
(4) Boron compounds: borax and boric acid; borax and zinc chloride; boric acid and ammonium borate; boric acid and magnesium borate; boric acid and triethanolamine, etc.
(5) Chlorinated paraffin: chlorinated paraffin plus phosphoric acid; chlorinated paraffin plus antimony oxide, chlorinated paraffin borax and boric acid.
(6) Dicyandiamide: dicyandiamide borax, ammonium sulfate and ammonium phosphate; dicyandiamide and phosphoric acid; dicyandiamide, ammonium sulfamate and boric acid.
(7) Metal salts: magnesium sulfate and sodium silicate; zirconium oxide, iron pyrophosphate; copper, titanium or zirconium salts.
(8) Others: zinc, titanium and silicon compounds, and their derivatives with urea.
7.1.2 Semi-Durable Fabric Fireproof Flame Retardant Finishing
(1) Urea-phosphoric acid method: the treatment solution is mainly phosphoric acid and urea, the molar ratio of which is 1:4, the solid content is about 68%, and the rolling-baking-baking process is adopted. The treated fabric requires a phosphorus content of 3%, part of the cellulose denaturation is: 20, CelF-O-P-ONH4ONHA product strength loss is greater. If ammonium salt is used instead of phosphoric acid, the effect is better. The urea-dihydrogen ammonium phosphate method is more widely used abroad.
(2) Phosphoramide method: Phosphoramide is generated by the action of phosphoryl chloride and ammonia, and contains 34% phosphorus and nitrogen. Padding 20%-25% of the solution, using a pad-bake-baking process, 150 ℃, 5min can be cured on the fabric. The weight gain of the fabric is about 14%, and the strength of the fabric can be maintained at 90%-95%, but the weather fastness is poor.
(3) Phosphate cellulose: Phosphate and cellulose can undergo esterification reaction. The cotton fiber is phosphatized with phosphorus oxychloride in pyridine, and then treated with ammonia water, using a pad-bake-baking process. After treatment, the fabric contains 9% phosphorus, but the fabric strength loss is large.
(4) THPC-Dicyandiamide: Add THPC (tetrahydroxymethyl phosphorous chloride) by the phosphoric acid-dicyandiamide method, the molar ratio of dicyandiamide to THPC is 2:1, and phosphoric acid is 2%-25%. Using the rolling-bake-bake process, 140~160℃, bake for 2-5min, the weight of the fabric will increase by 25%-30%, and it can be washed more than 30 times. If diammonium phosphate is used instead of phosphoric acid, the washing resistance can be increased to 50 times. The fabric feels soft.
(5) FWWMR method: that is, fire prevention, water, climate and mildew prevention finishing. Generally, chlorinated organics and metal oxides are used as flame retardants, organic adhesives are used as waterproofing agents, colored paints are used as weatherproofing agents, and a small amount of mildewproofing agents are added. This product is an important washable product in the United States and is widely used in military tent fabrics.
7.1.3 Permanent Flame Retardant Finishing
Permanent flame retardant finishing is a flame retardant finishing based on THPC. THPC is the first phosphorus-based flame-retardant finishing agent used by the Southern Research Institute of the United States for cotton. It easily reacts with ammonia, primary amine, secondary amine, urea, melamine and other amide compounds to form a three-dimensional network structure containing PCN bonds. As a result, many flame retardant finishes centered on TPC have been developed. Many flame retardants have also been developed on this basis.
(1) THPC amide method: THPC17%, hydroxymethyl melamine 10%, urea 10%, triethanolamine 1%-4%, finishing by rolling-bake-baking process. The fabric is very washable. However, the feel is slightly harder and the strength is greatly reduced.
(2) THPC-Antimony Oxide-Organic Chloride: Add antimony oxide and organic chloride, such as polyvinyl chloride and chlorinated paraffin, to the formula. The amount used is larger than the THPC amide method, which can further improve the flame retardancy. Has been widely used.
(3) THP-brominated allyl phosphate (or phosphazene flame retardant): Brominated allyl phosphate or allyl phosphazene chloride can be directly added to the THPC amide formulation in the form of a water emulsion. This kind of adduct has a higher flame retardant effect, but its application is limited due to its higher price.
(4) THPC-cyanamide: using THPC, cyanamide and phosphoric acid in an aqueous solution, the cotton fabric finished by the rolling-bake-baking process has good flame retardancy, the fabric has good appearance and feel, and the flame retardant has a good effect on the shade. no effect. However, the tear strength of the fabric loses about 50%. The flame retardant can inhibit the generation of smoke. Suppressing the amount of smoke generated when the fabric burns is a major topic of current flame retardant research, so the application research of this flame retardant is promising.
(5) THPC conversion THPOH: The product of the reaction of THPC and sodium hydroxide is THPOH, and it is still not possible to describe this substance completely. The pH value of THPOH solution cannot exceed 75~7.8.
The fabric finished with THPOH added with ammonia flame retardant does not harden, and the fabric strength increases to 25% of the original fabric.
THPOH adds flame retardant of methylol melamine and urea, the finished fabric feels soft and its strength is reduced by 10%~20%. Therefore, it is widely used in fabrics such as sheets.
THPOH and copper salt form a complex flame retardant at a molar ratio of 4:1. The price of this flame retardant is lower than THPOH. The processed fabric has a slight impact on the hand feel and strength. Copper gives the fabric a bluish tint.
(6) THPC-APO method: The mixture of THPC and APO (triaziridinyl phosphide oxygen) is a good flame retardant for cotton fabrics. After baking at 150℃ for 4min, these compounds can copolymerize and react with cellulose. The finished fabric is soft with 20% strength loss and 40% tear strength loss. The fabric has excellent durability. However, APO is toxic and has great chemical activity, so the operation must be very careful.
(7) Fyrol 76 (Fyrol 76): This flame retardant is produced by Stauff Chemical Plant in the United States. Its main component is vinyl phosphate and contains 22.5% phosphorus. Used in combination with methylol acrylamide, with persulfate as a catalyst. It is finished by rolling-bake-baking process, and the fabric has better washing resistance. The Flour 6, Flour 13, Flour 28, Flour HMP, etc. produced by the plant are also such phosphate esters. The Phos-con 76 of Meisei Japan is similar to Fyol 76. The similar product developed by Shaanxi Provincial Institute of Textiles is called SF-780.
(8) Proban: This law was proposed by the British Obray-Wilson Company. The use of ammonia curing method instead of thermal curing method has changed the traditional finishing process of forming a network structure through the hydroxyl group in the cellulose molecule and the cross-linking agent, which is a major development of THPC finishing. The process is: padding-drying-ammonia fumigation-oxidation-washing. Because of the cross-linking of NH3 and the methylol in the THPC/urea pre-condensed body during the ammonia fumigation process, the fabric feels very soft and has little strength drop, basically maintaining the comfort and durability of cotton fabric. The fabric can be washed 200 times. In order to improve the carcinogen bischloromethyl ether produced during the production of THPC, the company has produced THPS instead of THPC for use in children’s pajamas and bedding. Two sets of Proban flame-retardant finishing equipment have been introduced in Anshan and Beijing in my country, and both have been put into production.
(9) Pyrovatex CP (Pyrovatex CP): Pyrovatex CP is a flame retardant finishing agent produced by Swiss Ciba-Geigy Company. Because of its low toxicity, easy processing, and good flame retardancy, it has been widely used internationally. The scientific name of Pyrovatex CP is 0,0-dimethyl-N-hydroxymethylpropionamide phosphate. The flame retardant is used with a crosslinking agent to etherify melamine, urea and a catalyst, and the flame retardant is chemically combined with the cellulose through the crosslinking agent through a rolling-baking-baking process. The fabric has good washing resistance, soft hand feeling, and strength drop by about 20%-40%. Similar products have been produced in Shanghai, Changzhou, Tianjin and other places in China.
7.2 Flame-Retardant Finishing of Polyester Fabric
7.2.1 Temporary Flame-Retardant Finishing
There are not many applications of temporary flame-retardant finishing of polyester fabric. Phosphorus compound flame retardants are mainly used, which are mostly used in curtains and related fabrics in vehicles. The flame retardants used are: ammonium phosphate, carbamate, sulfate condensate, polyurethane phosphate, carbamoyl alkyl phosphate condensate, etc. When the flame retardant is 0-15% of the fabric, a good flame retardant effect can be obtained. The process is generally a rolling-bake-baking method.
7.2.2 Semi-Durable and Durable Flame-Retardant Finishing
The famous flame-retardant finishing agent (2,3-dibromopropyl) phosphate (TDBPP) was once widely used in polyester fabrics. Since its carcinogenicity was discovered in the late 1970s and production was discontinued, new polyester flame retardants have been developed at home and abroad, and the following are more commonly used.
(1) Cyclic phosphate oligomer: This type of flame retardant includes Antiblaze 19/19T from Mobil Corporation of the United States. my country has FRC-I in Changzhou. The flame retardant has good effect, low toxicity and small color change. Through the rolling-baking-baking process, the flame retardant penetrates into the polyester and is fixed, and the washing fastness is high.
(2) Hexabromocyclododecane (HBCD): This type of flame retardant includes CD75 from Great Lakes in the United States and Nikkafinon CG-1 from Nicca in Japan. This product is produced in my country’s Beijing and Zhejiang. HBCD can be used to prepare durable flame-retardant polyester by dye bath blending or padding and baking methods. Practice has proved that dyeing bath spelling is more advantageous. The flame retardant does not interfere with each other with disperse dyes and dyeing auxiliaries, and can be dyed in the same bath. The physical and chemical indexes of the fabric are similar to those of non-flame retardant fabrics with textile functional finishing.
(3) Decabromodiphenyl ether (DBDPO): Such products include Caliban F/RP-44 and F/RP-53 from White Company in the United States. Similar products are produced in Tianjin, Shanghai and Jiangsu in my country. The flame retardant is matched with an adhesive to treat the fabric by a rolling-bake-baking method, and depending on the bonding fastness of the adhesive, it can be prepared into a semi-durable and durable flame-retardant fabric.
7.3 The Flame-Retardant Finishing of Wool Fabrics
The early flame-retardant finishing of wool was impregnated with borax-boric acid solution, which was quickly eliminated due to its inability to wash. After 1960, with the increase in flame-retardant requirements, water-washable THPC began to enter the market, but it was soon discovered that this method was not suitable for wool because of the high cost, complex process, and weight gain of wool fabrics. Too much, it feels rough and hard, and loses the unique characteristics of wool, so this method is quickly replaced by metal complexes. Metal complex finishing can obtain satisfactory flame retardant effect without affecting the feel of wool. Commonly used metal complexes are: titanium-zirconium complex with carboxylic acid, titanium-zirconium complex with tungsten complex.
7.4 Flame-Retardant Finishing of Nylon Fabrics
The most common nylon fabrics are nylon 6 and nylon 66, and their flame retardants can be high-concentration phosphides, high-concentration halides, metal compounds and their complex sulfides.
7.5 Flame-Retardant Finishing of Acrylic Fabrics
Acrylic fabrics are easier to burn than nylon and polyester. There are not many effective and ideal methods for the flame-retardant finishing of acrylic fibers. Acrylic flame retardants are mainly some phosphorus, sulfur, nitrogen, and halogen. The compound, Apex Flameprllf 2084 from Aplex Chem, USA, is an organophosphorus bromide, which is currently a better flame retardant for acrylic fabrics.
7.6 Flame-Retardant Finishing of Blended Fabrics
So far, the most researched is polyester-cotton blended fabrics. Among the current flame retardants, F/RP44 and similar flame retardants of this type are more suitable for the flame retardant finishing of polyester-cotton blended fabrics. Its main components are: bromine-containing compounds and antimony trioxide, and then add appropriate viscosity. Mixtures (such as acrylates, etc.), where the bromide can be decabromodiphenyl ether.
7.7 Flame Retardant Finishing of Linen Fabric and Silk Fabric
7.7.1 The non-permanent flame-retardant finishing of hemp fabrics uses the following substances: borax-boric acid (7:3), diammonium hydrogen phosphate, chlorinated paraffin-antimony oxide. Semi-permanent flame-retardant finishing can use urea-phosphoric acid (1:1). The following substances are commonly used in permanent flame retardant finishing: THPC-triacetin-MM-urea (15:3:9:9), THPC-urea (24:6), THPOH-NH3.
7.7.2 The flame retardant finishing of silk fabrics can use the following flame retardant systems: THPC-triacetin-trimethylol melamine-urea (15:3:9:9), oxidized rubber-trimethylol phosphate A mixture of mono-toluene, monohydrate, ammonium phosphate and ammonium sulfate-emulsifier (sulfonated oil) (15:3.75:31.25:32:16:2).
8. Test Methods for Flame-Retardant Fabrics
8.1 Common test methods
Burning test is the most convenient flame-retardant test method. It does not require equipment and is simple to operate. It can also compare and evaluate the flame-retardant properties of fabrics. The test procedure is as follows: Sample size: 2.54cm×5.08m (1 inch × 2 inches). Combustion conditions: After the match is ignited, place it under the strip sample and burn until the match is burnt (about 15s). If the sample burns for less than 5s, it is qualified, and if it exceeds the midline or smolders for more than 15s, it is unqualified.
8.2 Oxygen Index Test Method
During the test, put the sample [12.7cm×0.63cm×0.32cm (5 inches×0.25 inches×0.125 inches)] vertically in the middle of the glass chimney, control the nitrogen and oxygen mixing ratio, and observe that the fabric can burn The minimum volume fraction of oxygen required is the oxygen index of the sample.
The oxygen index=[O2/(O2+N2)]×100
8.3 Other Methods
Other test methods include the smoke density test method, the carpet tablet test method, the U.S. Department of Commerce (DOC FF 3-71) test method, etc. Each method has its own test characteristics and is aimed at a certain flame retardant characteristic index. Or use the object to make special requirements.