Brief description of organic flame retardants and experimental results from Yinsu Company.

Brief description of organic flame retardants and experimental results from Yinsu Company.

Organic synthetic flame retardants, refers to organic synthetic flame retardants can be bromine, nitrogen and red phosphorus and compounds as a typical representative of a variety of inorganic flame retardants.

1. Halogen-containing organic flame retardants

Halogen-containing chemical flame retardants work: polymer auto-ignition process is a thermal oxidation reaction, when the halogen-containing elemental substances in the high heat degradation of halogen molecules, they will react with the hydrogen atoms within the polymer to generate hydrogen halide. Hydrogen halides can combine with free radicals formed during the combustion process and thus have a flame retardant effect on the oxidation reaction. Flame retardants containing bromine in the halogen group elements are effective.

Halogenated elements of flame retardants, in the usual combustion conditions after the dissolution of HX residue can improve the low-temperature dehydration of polymerized materials carbonization and thus generate flame retardant charcoal layer, which greatly reduces the number of low molecular number of cleavage products generated data, thus impeding the smooth progress of the ignition of the chemical reaction. Therefore halogenated flame retardants flame retardant effect is good, the increase is small, the characteristics of the composite material is also less negative impact. Due to the large amount of fuming, there is a strong corrosive nature of the emitted hydrogen halide exhaust, as well as the formation of highly toxic carcinogenic products of polybrominated dibenzo[a]oxo[a]ns and polybrominated dibenzofurans, which seriously jeopardize the healthy metabolism in the human body.

"On July 1, 2006, our country started to implement the "ROHS order to strictly control the application of PBDE and PBB.

2. Halogen-free organic flame retardants

(1) Phosphorus-containing flame retardants

Organic phosphorus as a flame retardant phosphate esters (such as bisphenol A bis (diphenyl) phosphate), phosphorus heterophenanthrene derivatives (DOPO and its derivatives ODOPB, etc.) and polyphosphorus nitrile (hexaphenoxy cyclic triphosphonitrile HPCTP and its hydrogen-substituted derivatives).

It is generally believed that the main flame retardant mechanism of the organophosphorus system is cohesive phase mechanism, that is, phosphorus-containing compounds in the heat of combustion decomposition into phosphoric acid and other non-combustible liquid film, phosphoric acid dehydration to get metaphosphoric acid, polymer with metaphosphoric acid to get the formation of viscous or liquid film of poly(metaphosphoric acid), and wrapped in the harmful substances, and phosphoric acid and poly(metaphosphoric acid) are strong acids, can be dehydrated to deal with the flame-retardant polymers and carbonized to produce a carbon layer, and therefore these liquid and solid membranes. Therefore, these liquid and solid membranes are able to prevent the escape of free radicals and have the effect flame retardant function of isolating indoor air, with a high flame retardant efficiency of up to 4-7 times that of bromide.

The decomposition of APP, PEPA and DOPO is triggered by the breaking of N-O, P-0 and P-II bonds respectively. The addition of phosphorus flame retardants can effectively reduce the release of harmful gases such as CH.O and co P elements are biased during pyrolysis to produce POz, PO4, or complex PO-P-0 structures, which are connected to carbon fragments to form residual carbon structures with P elements as the core. Small amounts of NH3, NO, and N2 products are found in the EP/APP system, which dilute the flammable gas molecules during the pyrolysis reaction to achieve flame retardancy."

(2) Silicon flame retardants

Organosilicon series of fire retardant in the process of its spontaneous combustion will appear earlier in the melt tic state, these organic synthetic silicone fire retardant melt drop products through the pores of the polymer matrix passed to the surface layer of the substrate, thus forming a dense and solid silicon-containing (mainly SiO2) charcoal layer This silicon-containing charcoal layer not only inhibits the combustible dissolution of highly flammable products of the escape, and also has the function of thermal insulation and oxygen barrier, you can Inhibit the thermal decomposition of polymer materials, thus realizing the purpose of high flame retardancy, low smoke and low toxicity.

The inorganic flame retardant STNS can promote PC cross-linking at high temperature, thus effectively improving PC's maister resistance and thermal stability. In addition, the addition of a certain amount of STNS can also significantly improve the hardness of flame-retardant PC, in which when the dose of sTNS reaches seven percent, the impact strength and elongation at break of flame-retardant PC increase by eighty-nine point nine percent and one hundred and eighty-seven point seven percent in that order, whereas its bending and tensile strengths decrease by two point seven percent and zero point seven percent in that order."

(3) Nitrogen-containing flame retardants

The development of nitrogen-based inorganic flame retardants is relatively late, of which melamine and melamine gas derivatives are the more common nitrogen-based inorganic flame retardants. Nitrogen-based flame retardants, in a high heat environment will decompose refractory gases such as N2, NH3 and water vapor, these gases can absorb heat from the polymer matrix and cool the matrix.

At present, the key development direction of this type of inorganic flame retardant is the diazo-based inorganic flame retardant with higher nitrogen content, heat resistance and flame retardancy. The higher the value of LoI theory, the higher the difficult level of combustion grade. When the newly selected nitrogen-containing flame retardants and acrylate UV coatings are blended, the material reliability performance will also be significantly improved, so the LOI value increased from the initial twenty-one to twenty-seven, thus exceeding the flame retardant level. The compatibility with UV coatings is also improved because these nitrogen-containing flame retardants are light-curable and reflective, and the higher the quantity of POP-290, the higher the gel quality. The higher the amount of POP-290, the higher the gel quality, while the higher the amount of POP-290, the lower the reliability: DsC analysis showed that the flame retardant increased the glass transition temperature (Tg) of the UV material.

These results show that the flame retardant effect of UV-curable materials can be achieved by using mixed ammonia-based inorganic flame retardants, which in turn can be used to achieve the effect of flame-retardant modification of light-curable materials."

Comprehensively, organic halogenated flame retardants have better fire retardant performance, and the use of small amounts, not only has a high adhesion, but also high temperature and ultraviolet (UV) performance. It contains halogen phosphate ester type, volatile type is small, colorless and odorless, resistant to degradation. 

However, this type of flame retardant in the incineration of soot content is larger, and the same release of halogenated sulfur gas there is a strong erosive, so often lead to secondary environmental pollution. And halogenated flame retardants in the fire after incineration can also emit halogenated dibenzodioxin (PBDD) and dibenzofuran, the body's immunity and regeneration system constitutes damage. 

At present, the organic halogenated flame retardants have been toward the renewable, higher simple, high chemical safety and high chlorine content of the development trend.