Phosphorus flame retardants are a type of flame retardant material with phosphorus as the core, which delays or inhibits the combustion process through condensed phase or gas phase mechanism. The following are its common classifications and representative compounds:
- Inorganic phosphorus flame retardant：
（1）Red phosphorus
Used directly in the form of elemental phosphorus, it is highly efficient but easy to absorb moisture and needs to be coated (such as epoxy resin coating).
Application: engineering plastics (PA, PBT), rubber, etc.
（2）Phosphate Ammonium polyphosphate (APP): the core component of intumescent flame retardant, used in combination with pentaerythritol (PER) and melamine (MEL).
Diammonium hydrogen phosphate, ammonium dihydrogen phosphate: used for flame retardant of wood and textiles.
Hypophosphite (such as aluminum hypophosphite)
High temperature resistant, suitable for high temperature processing of plastics (such as PBT, PET).
- Organophosphorus flame retardants：
（1）Phosphate esters
TCPP (trichloropropyl phosphate): commonly used in polyurethane foam (sofas, mattresses).
TDCPP (tris(dichloropropyl) phosphate): high flame retardant efficiency, but partially limited (potential toxicity).
TPP (triphenyl phosphate): used in PC/ABS alloys and electronic device housings. TEP
（2）Phosphonates
Dimethyl methylphosphonate (DMMP): high-efficiency liquid flame retardant, used in polyurethane and epoxy resins.
（3）Phosphine oxides
TPO (triphenylphosphine oxide): resistant to hydrolysis, suitable for engineering plastics.
（4）Phosphaphenanthrene derivatives
DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide): high heat resistance, used in epoxy resins (PCB substrates).
- Phosphorus-nitrogen synergistic flame retardant：
（1）Intumescent flame retardant (IFR)
Typical formula: APP (acid source) + PER (carbon source) + MEL (gas source), forming an intumescent carbon layer.
Application: polyolefins (PP, PE), coatings.
（2）Phosphazenes
Hexaphenoxy cyclotriphosphazene: has both thermal stability and carbon-forming properties.
- Reactive phosphorus flame retardants：
By chemically bonding to the polymer chain, the durability is better:
* BDP (bisphenol A-bis(diphenyl phosphate)): used for PC/ABS alloys.
* Phosphorus-containing polyols: used as monomers for polyurethane synthesis.
* DOPO-HQ (DOPO and benzoquinone adduct): used for epoxy resin encapsulation materials. - Environmental regulations and trends in flame retardants:
The push towards halogen-free products is driving the growth of phosphorus-based flame retardants. However, some organophosphates, like TDCPP, face restrictions under REACH and RoHS due to environmental concerns. Research is focusing on eco-friendly alternatives such as DOPO derivatives and bio-based phosphates.
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Key applications include:
* Electronics: printed circuit boards (PCBs) and connectors (meeting UL94 V-0 standards)
* Building insulation: polyurethane and phenolic resin foams
* Transportation: interior components of vehicles (requiring low smoke and toxicity)
If you need detailed properties or application examples of specific compounds, you can discuss further!