Most of the flame retardants currently used are organic compounds of phosphorus and halogens or organic compounds combined with inorganic compounds, with a few using high molecular weight substances such as cyclic aromatic phosphoric acid vinegar and ethyl tetra Australian bisphenol A (polyester); Chlorinated polypropylene, hexadecane, oxalic acid (penta (o-phenylene)), phosphoric acid tri (o-phenylene) chloride paraffin, dimer of liulvhuanwuerxi, etc. (polypropylene); Halide systems containing synergists, organic phosphides (nylon); Vinyl chloride, vinylidene chloride, ethylene glycol, wuyanghuaerti, etc. (nylon), as well as phenoxyphosphonic acid, acetic acid phosphate (adhesive), etc.

Flame retardant mechanism

Flame retardants are closely related to combustion. Xin's viewpoint holds that combustion has four elements - fuel, heat source, oxygen, and chain reaction. Usually, fabric combustion is divided into three stages: thermal decomposition, thermal ignition (spontaneous combustion), and thermal ignition (combustion propagation). By using corresponding flame retardants to resist the four elements of different combustion stages, various flame retardant mechanisms and interrupted phase flame retardant mechanisms are formed.

Different flame retardant mechanisms produce different types of flame retardants. Regardless of the type of flame retardant, its flame retardant mechanism must always strive to increase the oxygen index of the fabric fiber products after flame retardant treatment. In other words, it is to achieve flame retardancy by making it difficult to reach the critical conditions for fabric combustion. Among them, the oxygen index is an important parameter, and the higher the oxygen index, the better the flame retardant effect. Normally, the oxygen index should not be less than 28. The Tianjin Fire Research Institute of the Ministry of Fire Protection has developed flame retardants with an oxygen index of 90.

Classification of flame retardants

Flame retardants mainly act in the condensed phase; Halogen containing flame retardants mainly act in the gas phase; Many organic phosphorus flame retardants act both in the condensed phase and in interrupting heat exchange.

Application of flame retardants

1. Flame retardant finishing of cotton fabrics

The flame retardant finishing of cotton fabrics has developed rapidly and is currently relatively mature in China. Flame retardants are basically self-sufficient and can be produced industrially. There are generally three methods for durable and flame-retardant finishing of pure cotton:

(1) Proban/ammonia fumigation process, the Proban method was first used for industrial production by WIISon in the UK. The traditional Proban method is the baking process after soaking and rolling with flame retardant THPC (tetra light methyl chloride). The improved process flow is: soaking and rolling flame retardant finishing drying~ammonia fumigation~oxidation~water washing~drying. Domestic companies such as Beijing Guanghua, Jiangyin Printing and Dyeing Factory, and Anshan Cotton Textile Printing and Dyeing Factory have introduced foreign additives and equipment for production. This is currently the process with good flame retardant effect, minimal fabric strength reduction, and minimal impact on hand feel. However, due to equipment issues, its promotion has been limited.

(2) PyrovatexCP finishing process. Domestic units such as Shanghai Pesticide Factory, Changzhou Chemical Research Institute, Tianjin Institute of Synthetic Materials, East China University of Science and Technology, and Qingdao Textile and Apparel Institute have already produced this additive. The product has good flame retardant performance and durability, and can withstand household washing 50 times or even more than 20 times. It has a good hand feel, but the strength is slightly reduced. There are 20-30 domestic manufacturers using this type of flame retardant.

(3) Temporary and semi durable flame retardant finishing of pure cotton - The flame retardant and washability requirements for fabrics such as electric blankets, wall coverings, and sofa fabrics are not very high. These products can be treated with temporary or semi durable flame retardant finishing. It can withstand mild washing from 1 to 15 times, but not soap washing. There are mainly borax boric acid process, hydrogen phosphate dibasic process, phosphoramide process, dicyandiamide process, etc.

The above process is not widely applied in industrial production of pure cotton fabrics. SFR-203 from the School of Textile and Apparel at Qingdao University is a semi durable flame retardant finishing agent.

2. Flame retardant finishing of woolen fabrics

Wool has a high moisture regain and ammonia content, so it has good natural flame retardancy. However, if higher standards are required, flame retardant finishing is necessary. The early flame retardant finishing of wool was achieved by impregnating it with borax and boric acid solutions, and the product was used for decorative fabrics on airplanes. This method has good flame retardant effect, but it is not resistant to water washing. After the 1960s, THPC treatment was adopted, which had good washing resistance, but the process was complicated, the hand feel was rough, and the character of woolen fabric was lost. The method studied by the Wool Bureau is to use complexes of Qin, Cuo, and light base acids to finish wool fabrics, achieving satisfactory flame retardant effects without affecting the hand feel of wool, and therefore widely adopted. There are mainly metal chelating finishing agents such as Qin, Cuo, and tungsten. Since the late 1980s, several domestic units have been researching and developing flame retardants and finishing processes for wool, achieving satisfactory results. The Tianjin Institute of Synthetic Materials has developed a composite WFR-866 series of flame retardants, one of which is WFR-866F (mainly composed of fluorine complexes) and the other is WFR-866B (mainly composed of humic acid). Tianjin Renli Woolen Mill, Beijing Woolen Mill, and Beijing Woolen Mill all use halogen flame retardants to treat fine and coarse spun products. The School of Textile and Apparel at Qingdao University has developed the SFW series of flame retardants for wool, and has collaborated with Jining Woolen Textile Factory and Weifang Second Woolen Textile Factory to develop pure wool flame retardant products. The flame retardant performance of the products has reached or exceeded the level of similar products at home and abroad.

At present, pure wool flame-retardant fabrics are mainly used in aircraft cabins, high-end hotels, and other carpets, curtains, wall materials, and military uniforms for Jundui school officials and above.

3. Flame retardant finishing of polyester fabrics

So far, no suitable ideal flame retardant has been found for the flame retardant finishing of polyester fabrics. Tri (2,3-dioxopropyl) phosphate vinegar (TDBPP) has a certain flame retardant effect on polyester, but it also has carcinogenic effects.