# Metal-Organic Frameworks as Promising Textile Flame Retardants: Importance and Application Methods
## 2 Textile Finishes
### Flame-Retardant Finishes  
Flame-retardant finishes, which belong to the class of chemical textile finishes, generally act by limiting the spread of fire and are referred to as FRs. FRs are chemical products added to materials to prevent combustion and/or slow the spread of fire after ignition [25]. This functionality for many fire-resistant textile applications [26; 27]. Flame-retardant additives are generally composed of organic and inorganic compounds of phosphorus (P), nitrogen (N), sulfur (S), halogens (Br, Cl, F), silicon (Si), aluminum (Al), magnesium (Mg), antimony (Sb), tin (Sn), boron (B), zinc (Zn), carbon (C; graphite), zirconium (Zr), titanium (Ti), and calcium (Ca). There are more than 175 chemical substances classified as flame retardants, and they are divided into two groups: halogenated (brominated and chlorinated) and non- halogenated (phosphorus, nitrogen, and melamine derivatives) [28]. Examples of retardants are Proban(r) CC (tetrakis (hydroxymethyl)) phosphonium salt) developed by the French company Rhodia Solvay Group; Pyrovate(r) CP (N-hydroxymethyl-3-(dimethoxyphosphinacyl) propionamide) of the Chinese brand Drotex; Goldflam SU, belonging to the Golden Technology group in Brazil. The flame-retardant treatment of textiles can be carried out using various techniques, such as back-coating [29] (when the back of the fabric is coated so that the outside remainsunchanged), spraying, dip coating and filling. In recent years, innovative application techniques have been developed, such as sol-gel [30], layering [31], and plasma grafting [32]. The effect of the flame retardant is achieved by interfering with combustion at some stage of the combustion process and can act during heating, decomposition, ignition, combustion, or flame propagation [33]. There are five mechanisms by which these additives act: by gaseous dilution, thermal extinction, protective coating, physical dilution, chemical interaction, or a combination of these mechanisms [34]. Gaseous dilution involves the use of additives capable of producing large volumes of non-combustible gases during decomposition. By diluting the oxygen and reducing the amount of combustible material (polymer), flammability is reduced. This mechanism occurs in metal hydroxides, metal salts, and some nitrogen compounds [34]. Thermal quenching occurs through endothermic processes of the flame retardant that cool the substrate to temperatures below those required for pyrolysis to occur. Metal hydroxides, metal salts, and nitrogen compounds act in this manner [34]. Protective coatings limit the amount of combustible substrate available to the flame front by forming an insulating layer that reduces heat transfer from the flame. Phosphorus (P), melamine, and nitrogen compounds are examples of substances that use this mechanism [34]. Physical dilution acts by reducing the amount of combustible material and consequently increasing the flash point of the material [34]. Finally, flame retardants that interact chemically in the gas or condensed phase, such as halogens and some phosphorus compounds, act by dissociating into radicals that compete with the propagation chain stage in the combustion process [34]. In the gaseous phase, the radicals in the additives interact with the free radicals released by the decomposition, neutralizing them and thus drastically reducing the energy release and cooling the system [33; 35]. In the condensed phase, the additives act to form a carbonaceous layer. This carbonaceous layer inhibits the diffusion of pyrolysis gases into the gas phase and blocks the feedback of heat flow into the substrate by forming a thermal insulation barrier [33; 35; 36; 37; 38]. Although halogen additives are efficient, their use is limited due to their environmental impact. [PERSON], [PERSON], and [PERSON].