zinc borates for plastics

Introduction Firebrake® zinc borate is a multifunctional boron-based fire retardant with the chemical composition xZnO.yB2O3.zH2O. It imparts benefits to a wide variety of polymer compounds. Key benefits: Flame retardant in both halogen containing and halogen free systems Partial or complete replacement of antimony trioxide (Sb2O3) Smoke suppressant Afterglow suppressant Char and anti dripping promoter Lowers rate of heat release Anti arcing and anti tracking agent
Halogenated systems Firebrake® promotes zinc halide or zinc oxyhalide formation that accelerates the decomposition of halogen sources and promotes char formation. In halogen containing systems, Firebrake® is used in conjunction with antimony trioxide and alumina trihydrate. The zinc component catalyzes the decomposition of the halogen source to promote crosslinking and char formation. The borate component forms a glassy layer to protect the char from being further oxidized (afterglow suppression). The water given off can cool the flame and promotes the formation of an insulating char.
Halogen free systems Firebrake® promotes the formation of a low melting glass that stabilizes the char In halogen free systems, it is normally used in conjunction with alumina trihydrate, magnesium hydroxide, red phosphorus or ammonium polyphosphate. In some particular applications, zinc borate can be used alone. During polymer combustion, it can form a highly porous ceramic residue which protects the underlying unburned polymer or its substrate. In the presence of a silica source such as silicone polymer or SiO2, Firebrake is understood to form a borosilicate glass at polymer combustion temperatures. Firebrake® grades: Firebrake® ZB: combining zinc and boron oxides and water release for fire retardant formulations processable up to 290°C. Firebrake® ZB Fine: finer particle size for applications where maximum fire tests and mechanical performance are required. Firebrake® ZB XF: this grade has no particles greater than 12 microns, as determined by laser diffraction technique. Firebrake® 415: having higher zinc to boron ratio and much higher dehydration temperature, processable up to 415°C. Firebrake® 500: an anhydrous form of Firebrake® ZB, especially designed for applications where no water evolution is permitted.
Polymer resins Zinc borate can be used as a fire retardant in PVC, polyolefins, elastomers, polyamides, epoxy resins. Addition of Zinc borate in formulations provides to polymeric materials the following benefits: Polyamides: The choice to use Firebrake® ZB, 415 or 500 will depend on the specific nylon material, especially in halogen free polyamides. In these systems, zinc borate can inhibit afterglow and prevent burning drips.

Polymer Type	Benefits of Firebrake®	Applications
Flexible PVC, Rigid PVC	Smoke suppressant Flame retardant Synergist of antimony trioxide Char promoter	Conveyor belting, car interior trim, roofing membrane, flooring, wires & cables, wall coverings
Polyolefins, EVA	Smoke suppressant / Char promoter Afterglow suppressant Improves elongation properties Anti-arcing agent	Wire & cable, foam insulation, electrical parts
Polyamides	Anti-arcing and anti-tracking agent Synergist of halogen sources Afterglow suppressant Used in both halogen containing and halogen free nylons	Electrical components, adhesives
Elastomers, SBR, Silicone, EPDM, Neoprene	Smoke suppressant Afterglow suppressant Char promoter Anti-arcing and anti-tracking agent	Wire & cable, conveyor belting, roofing membrane, foam insulation, flooring insulator, coatings, sealants
Thermoset resins (Epoxy, Unsaturated Polyester, Urethane, Phenolics.)	Smoke suppressant Char promoter Partial or complete replacement of antimony trioxide	Intumescent coatings, encapsulant, panelling, containers, foam, adhesives, electrical parts

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