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Polyester Polyol for Flame Retardant

A flame retardant polyester polyol is a polyester polyol that has been chemically designed to have flame-retardant properties built directly into its molecular structure.

It's not just a standard polyester polyol mixed with additives. Instead, the flame-retardant elements (usually phosphorus) are part of the polymer chain, making them an integral and permanent feature.
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  • XF-2007; XF-250P; XF-235P

Product Overview


Flame Retardant Polyester Polyol Series comprises specialty polyols engineered to enhance fire resistance in polyurethane (PU) formulations, eliminating or reducing the need for additional halogenated flame retardants. These polyols integrate phosphorus, nitrogen, or intumescent additives into their molecular structure, with flame-retardant element content ranging from 8–15% depending on the grade. With a hydroxyl number of 200–450 mg KOH/g and functionality of 2.5–3.5, they are compatible with MDI, TDI, and PIR systems, forming rigid or flexible foams with UL 94 V-0 or ASTM E84 Class 1 fire ratings. Their low viscosity (3,000–15,000 cps at 25°C) ensures ease of processing in spray, pour, and injection molding applications.


Categories


To meet specific flammability standards (e.g., UL 94, ASTM E84), additional flame retardants are almost always incorporated. These can be divided into two categories:

A. Reactive Flame Retardants (Chemically Built-In)

These compounds contain functional groups (like -OH or -NCO) that react into the polymer backbone during the polyol synthesis or the PU formation. This is the preferred method as it creates a permanent, non-leaching flame-retardant effect.

  • Halogenated Diols/Acids: Historically common but being phased out due to environmental and health concerns (e.g., brominated compounds).

  • Phosphorus-based Polyols: This is the current industry standard for high-performance, environmentally friendly solutions. Phosphorus works in both the gas phase (radical quenching) and the condensed phase (promoting char).

    • Examples: Diethyl N,N-bis(2-hydroxyethyl)aminomethylphosphonate (a common reactive phosphonate polyol).

  • Nitrogen-containing Polyols: Often used in synergy with phosphorus (see below).

B. Additive Flame Retardants (Physically Mixed In)

These are compounded into the polyol blend or the final PU formulation. They are easier to use but can potentially migrate or leach out over time.

  • Phosphorus-based Additives:

    • Halogen-Free: Tris(1-chloro-2-propyl) phosphate (TCPP) is the MOST WIDELY USED flame retardant additive in flexible PU foam. However, for polyester polyol systems (often used in rigid foam or elastomers), other options like triphenyl phosphate (TPP) or dimethyl propyl phosphonate (DMPP) are common.

    • Inorganic: Ammonium polyphosphate (APP) is excellent for intumescent coatings.

  • Nitrogen-based Additives: Melamine and its derivatives (e.g., melamine cyanurate). They work by endothermic decomposition (cooling the material) and releasing inert gases that dilute fuel.

  • Inorganic Fillers:

    • Aluminum Trihydrate (ATH) or Magnesium Hydroxide (MDH): These are "mineral fillers." They decompose endothermically when heated, releasing water vapor which cools the material and dilutes flammable gases. They are very common but require high loading levels, which can affect mechanical properties.

    • Expandable Graphite: When exposed to heat, it expands dramatically to form a worm-like char layer, providing excellent insulation. Very effective in rigid foams and coatings.



Synergistic Effects


The most effective flame-retardant systems use synergists, where the combined effect is greater than the sum of the individual parts.

  • Phosphorus-Nitrogen (P-N) Synergy: This is extremely important. Nitrogen compounds (like melamine) enhance the char-forming efficiency of phosphorus. The nitrogen helps create a more stable, cross-linked, and protective char barrier.

  • Polyester Polyol + P-N System: This combination is a powerhouse. The char-forming tendency of the polyester backbone is significantly boosted by the P-N synergy, leading to high flame-retardant performance at lower overall additive levels.


Applications


Flame retardant polyester polyols are used to manufacture polyurethane products that must meet stringent safety standards:

  • Rigid PU Foam: Insulation for buildings, commercial refrigerators, industrial pipes. (e.g., must meet ASTM E84 standards).

  • Coatings: Protective coatings for steel structures, industrial flooring, and electrical components.

  • Elastomers: Wire and cable jacketing, gaskets, and rollers.

  • Adhesives & Sealants: Fire-rated construction adhesives.


Storage


Container: Store in stainless steel or HDPE drums to prevent contamination.

Conditions: Maintain temperatures at 10–35°C with humidity ≤60%, away from direct sunlight.

Handling: Avoid contact with strong oxidizing agents and acids, which may degrade flame-retardant groups.


Parameters


Product ModelHydroxyl value   (mgKOH/g)Acid Value   (mgKOH/g)Moisture                   (%)Viscosity                          (CPS 25℃)
XF-2007
200±10≤2.0≤0.115000±3000
XF-250P260±10≤1.5≤0.111000±2000
XF-235P235±15≤2.0≤0.15<3500


 




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