AMMONIUM POLYPHOSPHATE
Ammonium Polyphosphate
Ammonium polyphosphate (APP) is composed of polyphosphoric acid and ammonia in the chains.
It is reported to act mainly in the condensed phase to promote char formation with acid catalysis; but also in some cases dilute the flammable decomposition products with the release of non-flammable carbon dioxide in the gas phase.
Ammonium Polyphosphate
Ammonium poly-phosphate is a halogen-free flame retardant for unsaturated polyester resin composites.
Commonly used are ammonium polyphosphates having the general formula .
A significant reduction of the flame spread index is achieved by a combination of a polyhydroxy compound, a polyphosphate, melamine, cyanuric acid, melamine salts, e.g., melamine cyanurate, and a polyacrylate monomer.
The effect of aluminum trihydroxide in combination with ammonium polyphosphate has been investigated.
Thermogravimetric experiments revealed an improved thermal stability in the range of 200–600 °C.
Obviously, aluminum trihydroxide is more efficient than calcium carbonate in delaying the time of ignition and lowering the yield of carbon monoxide.
However, no significant synergistic effect in reducing the peak heat release was observed.
The fire retardant polyacrylate component should be distinguished from the unsaturated monomers that may be included as crosslinkers in the resin systems.
It cannot be ruled out that the polyacrylate may become involved in the crosslinking reactions of such systems.
However, it has been observed that the fire retardant effect of the polyacrylates is also effective in those resin systems that do not involve curing by way of unsaturated groups.
Preferred polyacrylates are those having backbones of a type that is known to contribute to char formation, for example those having alkylene or oxyalkylene backbones
Phosphorus-containing flame retardants
This category generally includes phosphate esters, ammonium orthophosphates, ammonium polyphosphates, and red phosphorus.
These retardants are oxidized during combustion to phosphorus oxide, which turns into a phosphoric acid on its interaction with water.
This acid stimulates the take-up of water out of the bottom layer of the material that has decomposed thermally, leading to char, thus increasing the carbonate waste as well as reducing the emission of combustible gases.
The phosphorous compounds work in the solid state, but can also operate in a gaseous state when they contain halogenated compounds.
This group represents 20% of the world flame retardant production.
Poly(methyl methacrylate) with Ammonium Polyphosphate
Several detailed studies have been made in which the fire retardant additive is ammonium polyphosphate (APP).
It is necessary first to understand the effect of heat on APP as the temperature is gradually increased.
In the temperature region 100–260 °C, less than 5% weight loss (as ammonia and water) occurs. Some free acid groups are formed, which condense to form crosslinks.
The physical state changes from powder to a glassy, hygroscopic solid, from which gas evolution is less easy.
The Psingle bondOsingle bondP links produced are easily hydrolyzed to acidic groups.
Between 260 and 350 °C the rate of evolution of NH3 and H2O goes through a maximum and declines to zero after 20% weight loss.
The product is polyphosphoric acid, a hygroscopic glass.
In the final stage above 350 °C (which may be too high a temperature region to influence some polymers), the polyphosphoric acid structure is fragmented with the formation of low volatility products.
The effects of APP are therefore likely to be due to one or more of these: evolution of NH3 and H2O, production of polyphosphoric acid or acidic species derived from it, and the glassy state of the intermediate decomposition product.
When PMMA is heated with APP, chemical changes in the PMMA occur only above 260 °C in the heating programme, i.e. after NH3 and H2O evolution has ceased and polyphosphoric acid is present.
The observed effects are believed to be due to mobile fragmentation products rather than the crosslinked polyphosphoric acid itself.20
The primary effect is to cause ester groups to be converted to anhydride rings, a small concentration of which is sufficient to interfere significantly with the depolymerization process.
Thus the production of monomer (which is the volatile fuel in a fire situation) is slowed down.
When the temperature is increased, the products include, in addition to monomer, methanol, CO2 and CO.
There is therefore a close parallel with the behaviour of PMMA in other acid-releasing environments, such as blends with polychloroprene.
The application of ammonium polyphosphate (APP) in different types of commodity thermoplastic composites (polyethylene, polypropylene (PP), polystyrene (PS), poly(methyl methacrylate) (PMMA) and poly(ethylene terephthalate) (PET)) have been discussed in terms of mechanical properties, morphologies and thermal properties.
In addition, engineering thermoplastics such as acrylonitrile-butadiene-styrene (ABS), polyamides and poly(vinyl alcohol) (PVOH) and their composites added with APP and other additives were analyzed as well.
It was suggested that improvement of mechanical properties and morphologies of the thermoplastic composites could be made possible with appropriate amount of APP and other additives such as montmorillonite (MMT), pentaerythritol (PER) and different types of layered double hydroxide (LDH). Furthermore, thermal properties such as limiting oxygen index (LOI) values together with cone calorimetry and thermogravimetric analysis (TGA) performance could be enhanced through optimum combination of APP, PER and melamine which functions as intumescent flame retardant (IFR).
APP-based flame retardants have been sold in the U.S., Europe, and Asia for several years.
In the U.S., they are used in the treatment of commercial furniture upholstery, automotive interior fabrics, draperies, and in other applications.
Outside the U.S., APPs are also used as flame retardants in commercial furniture upholstery.
Water-soluble forms of APPs are approved for use in food as a sequestrant and emulsifier.
Both LR2 and LR4 are used for semi-durable, flame-retardant (FR) application.
Water-soluble LR2 is applied to cellulose-rich upholstery fabrics.
Less-soluble LR4 is applied to fabrics as a latex back-coating.
Phosphorus is essential in human physiology.
Phosphate is a structural component of bones and teeth and is essential in many enzymatic processes.
AMMONIUM POLYPHOSPHATE
Ammonium salt of phosphoric acid. It is a high molecular weight fire retardant.
To achieve a synergistic effect, ammonium polyphosphate is added to the formulation of fire retardant coatings together with pentaerythritol or melamine.
ATAMAN KIMYA offers supplies of ammonium polyphosphate for the paint and varnish industry and the production of coatings for use in the production of such final products as:
intumescent fire-resistant coatings, for polyolefins (polypropylene, polyester and thermoplastic polyolefins)
polyurethane foams (hard, elastic and TPU)
thermosetting resins (epoxy, phenolic and unsaturated polyesters)
thermoplastic
textile coverings
paints
plywood
Ammonium Polyphosphate Exflam APP-201
Ammonium Polyphosphate Kylin APP-201
AMMONIUM POLYPHOSPHATE
Description:
Ammonium polyphosphate II crystalline phase.
Application:
intumescent fire-resistant coatings, for polyolefins (polypropylene, polyester and thermoplastic polyolefins)
polyurethane foams (hard, elastic and TPU)
thermosetting resins (epoxy, phenolic and unsaturated polyesters)
thermoplastic, textile coatings, paints, plywood.
CHEMICAL NAME
ammonium salt of polyphosphoric acid
CAS
68333-79-9
APPLICATIONS
Fire retardant coatings
AMMONIUM POLYPHOSPHATE
Description:
Ammonium polyphosphate II crystalline phase. Ammonium Polyphosphate is an environmentally friendly flame retardant with nitrogen structure and halogen free.
Properties:
high degree of polymerization
good heat resistance
low hygroscopicity.
This product is a highly effective inorganic flame retardant.
Application:
for the production of fire retardant intumescent paints, varnishes and sealants for coatings of metal structures, cables and wood
in the production of products on a wooden basis (chipboard, fiberboard, plywood)
in the synthesis of a wide range of resins and plastics with reduced combustibility, flammability, smoke-forming ability, toxicity of combustion products and with reduced flame spread over the surface
in the production of fire-resistant compounds based on rubbers, rubbers, artificial leather, lubricants.
Ammonium polyphosphate commercially produced by Clariant, (former business area of Hoechst AG), Budenheim and other sources is an inorganic salt of polyphosphoric acid and ammonia
containing both chains and possibly branching. Its chemical formula is [NH4 PO3]n(OH)2 showing that each monomer consists of an orthophosphate radical of a phosphorus atom with three
oxygens and one negative charge neutralized by an ammonium cation leaving two bonds free to polymerize. In the branched cases some monomers are missing the ammonium anion and instead
link to three other monomers.
The properties of ammonium polyphosphate depend on the number of monomers in each molecule and to a degree on how often it branches. Shorter chains (n<100) are more water sensitive and less thermally stable than longer chains (n>1000),[1] but short polymer chains (e.g. pyro-, tripoly-, and tetrapoly-) are more soluble and show increasing solubility with increasing chain length.
Ammonium polyphosphate can be prepared by reacting concentrated phosphoric acid with ammonia.
However, iron and aluminum impurities, soluble in concentrated phosphoric acid, form gelatinous precipitates or "sludges" in ammonium polyphosphate at pH between 5 and 7.
Other metal impurities such as copper, chromium, magnesium, and zinc form granular precipitates.
However, depending on the degree of polymerization, ammonium polyphosphate can act as a chelating agent to keep certain metal ions dissolved in solution.
Ammonium polyphosphate is used as a food additive, emulsifier, (E number: E545) and as a fertilizer.
Ammonium polyphosphate (APP) is also used as a flame retardant in many applications such as paints and coatings, and in a variety of polymers: the most important ones are polyolefins, and particularly polypropylene, where APP is part of intumescent systems.[6] Compounding with APP-based flame retardants in polypropylene is described in.Further applications are thermosets, where APP is used in unsaturated polyesters and gel coats (APP blends with synergists), epoxies and polyurethane castings (intumescent systems).
APP is also applied to flame retard polyurethane foams.
Ammonium polyphosphates as used as flame retardants in polymers have long chains and a specific crystallinity (Form II).
They start to decompose at 240 °C to form ammonia and phosphoric
acid. The phosphoric acid acts as an acid catalyst in the dehydration of carbon-based poly-alcohols, such as cellulose in wood.
The phosphoric acid reacts with alcohol groups to form heat-unstable phosphate esters.
The esters decompose to release carbon dioxide and regenerate the phosphoric acid catalyst.
In the gas phase, the release of non-flammable carbon dioxide helps to dilute the oxygen of the air and flammable decomposition products of the material that is burning.
In the condensed phase, the resultant carbonaceous char helps to shield the underlying polymer from attack by oxygen and radiant heat.
Use as an intumescent is achieved when combined with starch-based materials such as pentaerythritol and melamine as expanding agents.
The mechanisms of intumescence and the mode of action of APP are described in a series of publications.
Ammonium polyphosphate is an inorganic salt of polyphosphoric acid and ammonia containing both chains and possibly branching.
The properties of ammonium polyphosphate depend on the number of monomers in each molecule and to a degree on how often it branches.
Shorter chains (n < 100) are more water sensitive and less thermally stable than longer chains (n > 1000).
Consequently, short polymer chains and oligomers (e.g. pyro-, tripoly-, and tetrapoly-) are more soluble and show decreasing solubility with increasing chain length.
Ammonium polyphosphate (APP) is used as a flame retardant in many applications such as paints and coatings, and in a variety of polymers: the most important ones are polyolefins, and particularly polypropylene, where APP is part of intumescent systems.
Compounding with APP-based flame retardants in polypropylene is described in.
Further applications are thermosets, where APP is used in unsaturated polyesters and gel coats (APP blends with synergists), epoxies and polyurethane castings (intumescent systems).
Ammonium polyphosphates as used as flame retardants in polymers have long chains and a specific crystallinity (Form II).
They start to decompose at 240 °C to form ammonia and polyphosphoric acid.
The phosphoric acid acts as a catalyst in the dehydration of carbon-based poly-alcohols, such as cellulose in wood.
The phosphoric acid reacts with alcohol groups to form heat-unstable phosphate esters.
The esters decompose to release carbon dioxide and regenerate the phosphoric acid catalyst.
In the gas phase, the release of non-flammable carbon dioxide helps to dilute the oxygen of the air and flammable decomposition products of the material that is burning.
In the condensed phase, the resultant carbonaceous char helps to shield the underlying polymer from attack by oxygen and radiant heat therefore preventing the pyrolysis of the substrate.
Use as an intumescent is achieved when combined with polyalcohols such as pentaerythritol and melamine as expanding agent.
The mechanisms of intumescence and the mode of action of APP are described in a series of publications.
Due to its uncritical toxicological and environmental profile, ammonium polyphosphate has the potential to widely substitute halogen-containing flame retardants in a series of applications like flexible and rigid PUR-foam and thermoplastics.
Soluble ammonium polyphosphate (SAPP) is employed to prepare flame retardant semirigid polyurethane foam (SPUF) using water as blowing agent.
The flame retardant property of SPUF is evaluated by limiting oxygen index (LOI) and horizontal burning test
Polyurethane foam is regarded as a versatile polymeric material for its comparatively excellent properties such as low density, high specific strength, great insulation, large specific surface area, and good sound-absorbing performance.
Polyurethane foam is more easily burned compared to other foams since there are many easily decomposing urea bonds in it.
Thus, it is necessary to improve the flame retardant property of polyurethane foam
Ammonium polyphosphate (APP), as inorganic phosphorus flame retardant with nitrogen-phosphorus synergistic intumescent effect, has the advantages of thermal stability and lasting effect.
APP can also improve the mechanical properties of the material, so it is often used with other flame retardants, and the most common APP flame retardant studied by researchers is form II, of which the polymerization degree is greater than 1000.
In this paper, the water blown SPUF is synthesized only with soluble ammonium polyphosphate (SAPP) with a low polymerization degree.
Our aim is to study the effect of SAPP on the thermal degradation, the flame-resistant, and the mechanical properties of the SPUF.
Ammonium Polyphosphate (APP), Cas No 68333-79-9, is an environment-friendly and halogen-free flame retardant. APP is the main constituent of many intumescent flame retardant systems: coatings, paints and engineering plastics.
For the chemical point of view, Ammonium Polyphosphate is an inorganic salt of polyphosphoric acid and ammonia. Depending on the polymerization degree, there are two main families of ammonium polyphosphate: Crystal phase I APP (or APP I), and Crystal phase II APP (or APP II).
- APP phase I has a short and linear chain (n < 100), it is more water sensitive (hydrolysis) and less thermally stable; actually it begins to decompose at temperatures above 150 °C.
- The second family of Ammonium polyphosphate is the APP Phase II; which has an high polymerization degree, with n>1000, its structure is cross linked (branched), and it is an high-quality non-halogenated flame retardant.
APP phase II, Ammonium polyphosphate, has an higher thermal stability (the decomposition starts at approximately 300°C) and lower water solubility than APP I.
