Can be used for the flame retardant polypropylene variety, according to the chemical composition can be classified into two categories: organic flame retardants and inorganic flame retardant; According to the using method is divided into reactive and add. The typical flame retardant with bromine, phosphorus and nitrogen, phosphorus and aluminium hydroxide, magnesium hydroxide, etc.
1, the bromine flame retardants
Due to C - Rr key of key is low, most of the bromide flame retardants will break down under the 200-300 ℃, the temperature range was also polypropylene decomposition temperature range, so the polypropylene thermal decomposition, the bromine flame retardants are also beginning to decomposition, and can capture the degradation reaction of free radicals, to slow or stop the combustion chain reaction. At the same time release gets itself is a kind of hard to flammable, the gas density is big, can cover on the surface of material, have the effect of blocking surface combustible gas, also can restrain the combustion of material.
Bromide flame retardants in pp flame retardant application has an important position, the current main products have ten pbdes, tetrabromobisphenol A, e four four bromine two season, five bromide bromide polystyrene, toluene and hexabromocyclododecane, etc. Bromine series flame retardant are the main disadvantages of reducing the uv stability of flame retardant base material, the combustion generated when more smoke and toxic gases, corrosive gases, make its application is limited by a certain.
2, phosphorus - nitrogen flame retardants
Phosphorus - nitrogen flame retardant is also called the expansion type flame retardant, contain this kind of flame retardant polymer when heated, surface is able to generate a uniform layer of the carbon foam layer, insulation, oxygen and smoke suppression effect, and prevent the phenomenon of molten drops, it has a good flame retardant performance. Phosphorus - nitrogen flame retardant, low smoke, low toxic.
Expansion type flame retardant generally consists of three parts: acid source (dehydrating agent), carbon source (carbon) and air (nitrogen source and foaming source). Expansion type flame retardant mainly through the formation of porous carbon foam layer plays a role of flame retardant in the condensed phase.
3, phosphorus-containing flame retardants
Phosphorus-containing flame retardant on flame retarding effect on getting high polymer, beginning of decomposed two carbide dehydration, the dehydration step must rely on carbide oxygen-containing groups of the polymer itself, for itself with oxygen-containing groups of the polymer structure and their fire retardant effect will be better. For polypropylene, due to the molecular structure of itself without oxygen containing groups, when used alone phosphorus-containing flame retardant flame retardant effect is not good, but if with (OH) 3 and the distribution of such as Mg (OH) 2 can produce synergies, good flame retardant effect is obtained.
Commonly used organic phosphorus flame retardants are three triphenyl phosphate, phosphoric acid methyl ester, phosphate ester (xylene)
, propyl benzene phosphate ester, styrene butadiene, phosphate, etc. The characteristics of phosphate ester is a flame retardant and plasticizing dual function. It can make the halogen free flame retardants, the plasticizing flow function can make the plastic molding processability, inhibits the residue after burning. The toxic and corrosive gas less than phosphorus-containing flame retardants. Its main advantages are high efficiency, light stability or light stabilizer effect is small, the influence of corrosive processing and the combustion of small, have the effect of the block again, little or no increase the quality of the flame retardant materials. But most of the phosphate ester flame retardant also exist some disadvantages, such as heat resistance is poor, volatile, compatibility is not ideal, and the burning has drop objects, etc.
The main products are inorganic phosphorous flame retardant red phosphorus flame retardants, ammonium phosphate, ammonium polyphosphate, etc. With the increase of dosage of halogen-free flame retardant materials, also in the increase in the amount of red phosphorus flame retardants, red phosphorus flame retardant effect is better than phosphate ester flame retardant effect, inorganic phosphorous flame retardant because of its good thermal stability, non-volatile, does not produce corrosive gas, long-term effect, and low toxicity of two get extensive application.
4, aluminum hydroxide, AL (OH) 3 (ATH)
Between 200-300 ℃ decomposition, heat absorption capacity of 1967.8 j/g, is a concentration of flame retardant and smoke suppression, filling the three functions in one of the flame retardant. It is non-toxic, non-corrosive, good stability, non-volatile, the advantages of high temperature does not produce poisonous gas, and the price cheap, sources. But as flame retardants, it also has a large amount of filling and the shortcoming of mechanical performance and processability variation. AL (OH) 3 starts to break down the temperature is in the midst of the polymer from the process of condensed phase changing into liquid phase, so the early temperature rise to the inhibition of polymer material. When AL (OH) 3 is added when the mass fraction of 40%, can significantly reduce thermal decomposition of materials, flame retardant and smoke reduction effect.
5, magnesium hydroxide,
Magnesium hydroxide decomposition, between 340-490 ℃ heat absorption capacity of 782.9 j/g, good thermal stability, good flame retardant and smoke abatement effect, especially suitable for high processing temperature of polypropylene material. Mg (OH) 2 for PP (adding amount is more than 50%) has excellent flame retardant effect, is better than that of AL (OH) 3. Under the same filling amount, the ratio of different aluminum hydroxide, magnesium hydroxide, the flame retardant effect is not obvious difference, but the two kinds of compound use performed better than used alone, because although is a dehydration reaction, but there are differences on the decomposition temperature and heat absorption capacity. Magnesium hydroxide need at higher temperatures to dehydration, and at the same time have a carbonization effect, two magnesium hydroxide heat absorption is relatively small, the effect of temperature rise due to its inhibition materials as aluminum hydroxide, the compound use can complement each other, the flame retardant performance is better than single use effect. But Mg (OH) 2 has resistance to acid and poor dispersion and poor compatibility shortcomings, to develop good compatibility of new varieties.
