Zinc borate hydrate

Zinc borate hydrate is another hydrated filler for rubber, which imparts flame retardancy properties. A specific zinc borate hydrate with a composition of ZZnO-SBjOa S.SHjO is a form commonly used and found effective for flame retardancy. 

Zinc borate hydrate is used in the rubber industry as a flame-retardant additive. It works by promoting the formation and stabilization of a char, which helps cut off the fuel source to the flame. The water of hydration also helps impart flame retardancy. 

It is also used as a flame retardant for textiles, as a flux in ceramics, and as a fung-istat. 

Other flame retardants are available that can substitute for zinc borate hydrate however, the compound must be reformulated to meet other product physical property requirements. 

---

Zinc borate hydrate is produced as follows in Figure 11.52. 

Borax is used to produce boric acid, which is used to make zinc borate hydrate (a flame-retardant additive used in rubber compounding). 

Boric acid is reacted directly with zinc oxide to produce zinc borate hydrate, a commonly used flame retardant. 

Zinc Borates. A series of hydrated 2inc borates have been developed for use as fire-retardant additives in coatings and polymers (59,153). Worldwide consumption of these 2inc salts is several thousand metric tons per year. A substantial portion of this total is used in vinyl plastics where 2inc borates ate added alone or in combination with other fire retardants such as antimony oxide or alurnina trihydrate. 

High Dehydration Temperature - In contrast to other forms of zinc borates, the water of hydration of the zinc borate is retained up to 290°C, thus allowing it to be used in polymers requiring high processing temperatures. The proposed molecular structure for the zinc borate is depicted in Fig. 

This anhydrous zinc borate is recommended for use in engineering plastics processed at temperatures higher than 300°C which is the upper limit of Firebrake ZB processing temperature. It is reported to be an effective smoke suppressant in chlorofluoropolymers for plenum cable applications.66 Recently it was claimed that this anhydrous zinc borate can replace antimony oxide (or sodium antimonate) completely in high temperature polyamide applications. Like its hydrated analog, this anhydrous zinc borate can also improve CTI, thermal stability, and the color stability of polyamide containing halogen sources.67 68... 

Boric acid (H4B6O11), zinc salt (1 2), hydrate Boron zinc oxide (B6Zn20ii), hydrate (2 15) Caswell No. 909B EPA Pesticide Chemical Code 128859 Firebrake ZB ZB2335 Zinc borate. Zinc borate for flame retardancy. Borax Europe Ltd. 

As additives in the polymer industry, borates are valued primarily as fire retardants. The relevant chemical compounds are zinc borates, which have the important property that they tend to retain their waters of hydration at relatively high temperatures. This fact likely plays a role in the mechanism of retarding fires. Fires involving plastics containing zinc borates spread more slowly and they also produce less smoke. 

Firebrake zinc borates display an interaction with metal oxide partieles resulting from dehydrating metal hydrates in flame retardant polyolefins. The interactions taking place show that surface... 

Flame retardant (1947) n. A material that reduces the tendency of plastics to burn. Flame retardants are usually incorporated as additives during compounding, but sometimes applied to surfaces of finished articles. Some plasticizers, particularly the phosphate esters and chlorinated paraffins, also serve as flame retardants. Inorganic flame retardants include antimony trioxide, hydrated alumina, monoammonium phosphate, dicyandiamide, zinc borate, boric acid, and ammonium sulfamate. Another... 

Borax Einope and US Borax sell hydrated zinc borate flame retardants under the Firebrake name. Firebrake ZB is an example it has the formula 2ZnO.3B2O3.5H2O and the average particle size is seven microns. Firebrake 500 withstands high temperatures because it consists of anhydrous zinc borate, with no water to lose. It can be used in polyetherketones, polysulfones, fluoropolymers, polyesters and polyamides. It has a very beneficial effect on the heat release rate, suppresses smoke and afterglow, as well as promoting char. It is recommended for aircraft applications. 

---