Читать книгу Non-halogenated Flame Retardant Handbook - Группа авторов - Страница 31

The ammonium phosphate treatment of cellulosic materials (canvas, wood, textiles, etc.) has been known for almost three centuries [9]. However, only with commercialization of synthetic polymeric materials in the twentieth century, organophosphorus compounds have become an important class of flame retardants.

All phosphorus-based flame retardants can be separated into three large classes:

 • Inorganic represented by red phosphorus, ammonium phosphates and metal phosphites and hypophosphites.

 • Semi-organic represented by amine and melamine salts of phosphoric acids, metal salts of organophosphinic acids and phosphonium salts.

 • Organic represented by phosphates, phosphonates, phosphinates, phosphine oxides and phosphazenes.

Water-soluble phosphorus flame retardants are mostly used for topical treatment of wood, textile and other cellulosic products. Some water soluble FRs can be further reacted with cross-linkers (cured) which provides durable water resistant treatment. Water-insoluble phosphorus FRs find a very broad range of applications in thermoplastics, thermosetting resins, synthetic foams, coatings, etc.

Phosphorus flame retardants have certain advantages over other flame retardants (mostly halogen based) but also have some disadvantages which are both listed below:

Advantages:

 • Low specific gravity which results in light plastic parts

 • Achieve flame retardant efficiency at lower phosphorus content compared to the halogen content needed for the same rating

 • High comparative tracking index (CTI) test performance

 • Better UV stability than most halogen-based FRs

 • Less tendency to intensify smoke obscuration

 • Less acidic smoke compared to halogen FRs

 • Most phosphorus FRs are biodegradable and therefore not persistent or less persistent than halogen FRs

Disadvantages:

 • Low efficiency in polyolefins, styrenics and elastomers unless charring agent is added.

 • Absence of a good general synergist that works in most polymers.

 • Many phosphorus FRs are hydrophilic and possibly cause moisture uptake, limiting use in some applications.

 • May hydrolyze to give acids which decrease the molecular weight of acid-sensitive plastics (polycarbonates, polyesters, polyamides, etc.)

 • Recycling of acid sensitive polymers is problematic due to the hydrolytic instability of organophosphates.

 • Some phosphates are toxic to aquatic organisms. Some phosphates exhibit a certain degree of neurotoxicity.

 • Apart from a few selected cases, the cost/efficiency of phosphorus FRs is higher than halogen based FRs.