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Tetrabromophthalic Anhydride is a versatile brominated flame retardant and chemical intermediate widely used in unsaturated polyester resins, epoxy resins, and polyurethane foams. Recognized for its high bromine content (≈68%) and reactive nature, it integrates covalently with resin matrices—eliminating additive leaching and ensuring long-term flame-retardant performance. Unlike non-reactive flame retardants, it becomes part of the polymer’s chemical structure, enhancing compatibility and reducing the risk of migration (critical for food-contact or medical applications). With a melting point of ≈274℃ and decomposition temperature >300℃, it maintains stability during resin curing processes (typically 120–200℃), making it suitable for applications like fiberglass-reinforced composites, electrical laminates, and fire-retardant coatings. Its compliance with RoHS 2.0 and REACH SVHC further expands its use in global markets.
Tetrabromophthalic Anhydride is a reactive flame retardant—its anhydride group reacts with hydroxyl or amine groups in resins (e.g., unsaturated polyester, epoxy) to form covalent bonds. This integration ensures the flame retardant becomes part of the polymer’s backbone, eliminating leaching or migration even in harsh environments (e.g., exposure to water, solvents, or high temperatures). For example, in unsaturated polyester resins used for boat hulls, Tetrabromophthalic Anhydride remains bonded to the resin matrix, maintaining flame retardancy for the hull’s entire lifespan (up to 20 years) without reapplication.
With a bromine content of ≈68%, Tetrabromophthalic Anhydride delivers powerful flame-retardant performance. When integrated into resins, it releases bromine radicals during combustion that interrupt the combustion chain reaction, suppressing flame spread and reducing heat release. This allows resins to achieve strict flame-retardant ratings (e.g., UL94 V-0, GB/T 2408-2021) with addition levels as low as 10–15% (depending on the resin type). For instance, epoxy resins containing 12% Tetrabromophthalic Anhydride pass UL94 V-0 (1.6mm thickness) and reduce heat release rate (HRR) by 45% (per ISO 5660-1).
Tetrabromophthalic Anhydride is compatible with most resin curing systems, including free-radical curing (for unsaturated polyesters) and amine curing (for epoxies). It does not interfere with curing kinetics—maintaining the resin’s typical gel time (e.g., 10–30 minutes for unsaturated polyesters at 25℃) and final crosslink density. Its melting point of ≈274℃ is higher than most curing temperatures (120–200℃), ensuring it remains dissolved in the resin during curing and does not crystallize or separate. This compatibility ensures consistent resin performance, with cured composites retaining >90% of their original flexural strength.
Unlike non-reactive flame retardants that often reduce resin strength, Tetrabromophthalic Anhydride can enhance the mechanical properties of cured resins. Its rigid aromatic structure improves the resin’s flexural strength (by up to 15% in epoxy resins) and thermal stability (increasing Tg by 5–10℃). For example, fiberglass-reinforced unsaturated polyester composites containing Tetrabromophthalic Anhydride exhibit a flexural strength of ≈350 MPa—10% higher than composites with non-reactive flame retardants. This makes it suitable for structural applications like building panels and automotive composite parts.
Tetrabromophthalic Anhydride has low volatility (vapor pressure <1 Pa at 25℃), preventing loss during resin mixing and curing. It contains no free bromine or heavy metals (lead, cadmium), complying with RoHS 2.0 (2011/65/EU) and REACH SVHC (no listed substances). When used in food-contact resins (e.g., epoxy coatings for food cans), it does not leach into food—meeting FDA 21 CFR Part 175.300 standards. Its low toxicity (LD50 >5,000 mg/kg in oral rat tests) also ensures safe handling during production.
• CAS Number: 632-79-1
• Molecular Formula: C₈Br₄O₃
• Molecular Weight: 463.61 g/mol
• Bromine Content: ≈68% (by weight, determined via titration)
• Appearance: White to off-white crystalline powder (high purity, <0.5% impurities)
• Melting Point: ≈274℃ (range: 272–276℃, per ASTM D127)
• Decomposition Temperature: >300℃ (no significant decomposition below 300℃)
• Solubility: Soluble in acetone, methyl ethyl ketone (MEK), and dioxane; insoluble in water (solubility <0.1 g/L at 25℃)
• Particle Size: D50 ≈10–20 μm (optimized for dissolution in resins)
• Recommended Addition Level: 10–15% (unsaturated polyester resins); 12–18% (epoxy resins)
• Compatible Resins: Unsaturated polyester, epoxy, polyurethane, vinyl ester
• Curing Compatibility: Works with free-radical initiators (e.g., benzoyl peroxide) and amine curing agents (e.g., diethylenetriamine)
Tetrabromophthalic Anhydride is widely used in unsaturated polyester resins for fiberglass-reinforced composites (FRP), including boat hulls, building panels, and electrical enclosures. Adding 10–12% to UPR ensures FRP composites meet UL94 V-0 and GB/T 8624-2012 (B1 grade for building materials). For example, FRP building panels containing Tetrabromophthalic Anhydride resist fire spread in commercial buildings, complying with fire codes and reducing insurance costs for building owners.
In epoxy resins, it is used to produce electrical laminates (e.g., PCB substrates), fire-retardant coatings, and adhesive systems. Epoxy laminates with 12–15% Tetrabromophthalic Anhydride achieve UL94 V-0 and meet IEC 61249-2-21 (flame-retardant standards for PCBs). For instance, PCB substrates made from this epoxy blend are used in high-voltage electrical equipment (e.g., transformers), where flame retardancy and electrical insulation are critical.
Tetrabromophthalic Anhydride is integrated into rigid polyurethane foams used for building insulation and automotive seat cushions. Its reactive nature ensures flame retardancy is permanent—unlike additive flame retardants that wash out over time. Rigid foam insulation with 15% Tetrabromophthalic Anhydride meets ASTM E84 (Class A fire rating) for building insulation, reducing the risk of fire spread in walls and roofs. In automotive seat cushions, it complies with FMVSS 302, ensuring the foam self-extinguishes within 10 seconds of ignition.
It is used in intumescent and non-intumescent fire-retardant coatings for steel structures, wood, and concrete. When added to coating formulations (10–18%), it enhances flame suppression and reduces smoke emission. For example, steel beam coatings containing Tetrabromophthalic Anhydride protect beams from high temperatures during fires (maintaining structural integrity for up to 2 hours), complying with building codes for high-rise structures. Wood coatings with this flame retardant also prevent wood combustion, making them suitable for commercial furniture and public building interiors.
