flame retardant: flame retardant polypropylene and trends

 
Describes the polypropylene (PP) flame retardant type and mechanism of resistance ene agent PP summarized research progress and trends. Efficient, low toxicity,
Low smoke, low cost, versatile, new composite "green" flame retardant PP 21st century focus of the study.
Polypropylene (PP) is a hydrocarbon material, heat of combustion, it is not entirely produced by burning smoke and toxic gases, its application is limited. In order to improve flame retardant PP, broadening its field of application, you must add flame retardants.
A, PP fire retardant classification
PP flame retardant more categories, according to the basic performance is divided into inorganic and organic flame retardants; according to high and low molecular weight divided into low molecular weight and high molecular weight flame retardant; divided by use of additive flame retardant and reactive flame retardant. Which, by the use of method of classification is more commonly used classification methods. Flame retardant is added to the polymer processing with flame retardant liquids or solids, including phosphates, halogenated hydrocarbons such as, the advantage of ease of use, wide applicability; reactive flame retardant is contained Cl,, Br, P and other elements and reactive flame retardant class of compounds, are copolymerized with the resin to give a resin flame retardant.
Two, PP flame approaches, methods and mechanism (a), flame route
PP flame retardant mainly through three kinds of ways to achieve [1]: (1) using the additive flame retardant, the flame retardant added by mechanical mixing
To the polymer, to achieve flame purposes; (2) use of reactive flame retardant, the flame participate in the reaction as a reactive monomer,
Grafted to the polymer main chain or side chain, the modified polymer has a flame retardant; (3) a flame retardant polymer itself. (Two), the basic method of flame retardant
Retardant PP basic method comprising: (1) use of foam or non-foam refractory material coating the surface of PP material, to
With oxygen or thermal isolation; (2) through the modification of the modified PP matrix material flame retardant. The second method is the main method. (Three), flame retardant mechanism
1. Termination of a chain reaction mechanism
PP combustion, the general decomposition of hydrocarbons. Further oxidation of hydrocarbons at high temperatures, decomposition of free radical HO •. HO • The chain reaction
Makes the flame should continue. Halide decomposition of hydrogen halide (HX). HX can capture high-energy HO • and produce X • and
H 2O, while X • R • reacts with the polymer and the HX, but also capture the HO •. This cycle enables highly active HO • Less
Less will eventually contribute to the ripple cut HO • terminate hydrocarbon combustion flame to achieve the purpose. For PP, halides
Usually without the use of fluoride chloride or bromide or iodide. Because fluoride too lively, the formation of molecular fluorine and very stable
Iodine forming compound is unstable, it is rarely used.
2. Mechanism of protective film
Flame temperature in the combustion swells into a layer of non-combustible protective film covering the surface of the material, isolated from the air and fire retardant. In
Phosphate flame retardant in the PP phosphate, halogen hydrocarbon ester. They differentiate to form a layer of porous insulating film coke, separated
Absolutely air to prevent heat transfer, and thus play a role in flame.
3. Cooling mechanism
Flame retardant polymer surface can melt at a lower temperature, the latent heat absorbed or endothermic reaction, consume a lot of heat, from
And to prevent burning. Such as Al (OH) 3 can play in PP flame retardant effect. It is a non-flame-retardant filling aids. When the temperature
No more than 200 ℃, hydration molecules and Al (OH) 3 combined with very strong, even at 230 ℃ for continuous heating will not significantly decompose.
When the polymer is exposed to heat, one of the Al (OH) 3 hydrated plays the role of heat. When the temperature is higher than 250 ℃, the polymer combustion,
Al (OH) 3 decomposes to absorb a lot of heat, and generate water. Water vapor, and absorb a large amount of heat, thereby reducing the polymer
Temperature of PP pyrolysis gas combustion products, the speed is very slow, less than the concentration of combustion can be maintained, thereby preventing burning. Mg (OH) 3 and Al (OH) 3 is similar, but its decomposition temperature close to 350 ℃ PP is a good flame retardant effect.
4 synergy system mechanism (1) Antimony - halogen collaborative system
Antimony compounds are commonly used Sb 2O 3, halide is an organic halide. Its mechanism is Sb 2O 3 and HX, generating SbOCl; SbOCl
Thermal decomposition of SbCl 3. First, SbCl 3 can be a long stay in the combustion zone, dilution flammable gas, isolated from the air, from the
To flame retardant; secondly, to capture combustible radicals H •, HO •, CH 3 •, etc., play a role in suppressing the flame; thirdly,
SbCl 3 in flames over condenses into droplets type solid particles, the wall effect reactive scattering a lot of heat, so that the combustion slows down or stops,
HX it off after the formation of the polymer of the unsaturated compound to form a crosslinked polymer, improved thermal stability. (2) phosphorus - halogen collaborative system
Phosphorus - when used in conjunction with each other halo promote decomposition, the decomposition temperature lower flame, accelerated decomposition of flame, burning
Region is formed more strongly phosphorus halide compound and decomposition products, and the resulting gas can stay a long time in the combustion zone, to form a strong
Gas barrier layer, to achieve the purpose of fire. (3) phosphorus - nitrogen coordination system
Phosphorus - nitrogen-based flame retardant mechanism by thermal decomposition, releasing acid and nonflammable gas, in which the dilution air
Oxygen. Nitrogen-containing compound plays the role of a blowing agent and coke enhancer, and phosphoric acid is the coked catalyst for burning surface
Forming a layer of porous coke protective film, heat insulation and oxygen barrier effect, can interrupt the burning chain reaction.
Three, PP flame retardant research
Phosphorus - Bromine flame retardant system has a higher melting point, heat resistance and light resistance, their synergistic effect with. This class is used more flame retardant tris (2,2 - dibromo-3 - bromo-propyl) phosphate (TOBP). Bromine and Sb 2O 3 on the ratio of phosphorus -
Bromine flame retardant composites greater impact. Add appropriate amount of chlorinated polyethylene flame-retardant properties of the PP material is small, but it can serve to improve the impact strength. Pengzhi Han and other studies TDBP and TDBP mixed with Sb 2O 3 on PP flame retardant
And rheological properties, and found that they have a significant synergistic flame retardant effect, and PVC heat stabilizer for fittings  its rheological behavior is affected by temperature, shear rate
Rate and flame retardants greater impact.
Intumescent flame retardant polymer technology is in the mid-1970s, the development of a new type of flame retardant technology. It will contain
There are carbon, acid source and air source intumescent flame retardant additives and polymer blend processing, the formation of flame retardant materials. Intumescent flame retardant to
Former multi-ammonium polyphosphate (APP), polyols and melamine composite component composition. When APP thermal decomposition when generated with
Dehydration of the phosphoric acid and pyrophosphoric acid, the polyol esterification, dehydration carbonization, and ammonia produced by the reaction with water vapor to form a
Layer of porous carbon layer, the carbon layer expansion reached retardant purposes. The disadvantage of multi-retardant, impact PP performance. Researchers
The system was modified. In order to ammonium polyphosphate based intumescent flame retardants, triazine derivatives and triazine ring-containing polymer
Due to its excellent flame retardant material synergies attention has been paid, it is flame retardant technology research and development of a hot spot.
Liao Kairong etc. [7] found that adding a small amount in PP triazine derivative flame retardants, can greatly improve the PP flame retardant;
It was also found in a single hydroxyethyl melamine polyphosphate compound and composition of the best flame. Ma collar, etc. [8] studied with P 2O 5, pentaerythritol and melamine for raw materials intumescent flame retardant (IFR), 3 kinds of functions of the PP as IFR / PP body
Department of coupling agent on the mechanical properties, morphology and rheological properties, that the coupling agent and PP blends, because both
The same crystal structure, can be copolymerized, is conducive to the improvement of compatibilizer. The one kind of intumescent accelerator
Join APP / pentaerythritol intumescent flame retardant, as the PP, flame retardants. This new technology greatly improved flame retardant
The flame retardant effect of PP, limiting oxygen index is improved. By heat treatment and melamine ammonium polyphosphate
Mixture to obtain high thermal stability and low moisture absorption intumescent flame retardant. He believes that high temperatures, with the melamine modified
PP polylactic acid promotes the inganic pigments  combustion heat generated during the oxygen-containing organic compound and the unsaturated organic compound charring. Since
Expanding carbon layer shielding effect, so the accumulation of coke carbon layer phosphate favor of further carbonization coke material to accumulate in the melt
The surface of the oxygen-containing compound of phosphorus to form an acid layer have a barrier effect of the air.
Chiu et al [11] studied the halogen-containing flame retardants, flame retardant effect is very significant, but the large amount of smoke when burned, produces a large number of corrosive
Gases and toxic gases, causing environmental pollution, its application is limited. Halogen-free flame retardants less pollution, rapid development.刘敏江 etc.
Using red phosphorus, magnesium hydroxide, APP, pentaerythritol, melamine-halogen flame retardant, various flame retardant composition system,
Flame of PP conducted research and found that APP, pentaerythritol, melamine, between the red phosphorus flame retardant has a good synergy
Purposes. Retardant reduced tensile strength of PP, with the increase of flame retardants, increases the degree of tensile strength is reduced,
Can be reasonably complex between flame retardant synergy play.
Studied intumescent flame retardant system of PP retardant synergistic effects and the impact of liquidity,
The results show that: Collaborative Retardant PP significantly improved flame retardant properties, the droplet phenomenon completely overcome, suitable
Phosphorus, carbon, nitrogen ratio is the formation of high-quality carbon layer of assurance, smoke suppression effect significantly, significantly improved melt flow PP flame retardant system
Sex. Use Intumescent Flame Retardant for PP modified to solve the difficult process operation retardants, stable production
Poor two problems. Halogen-free flame retardant engineering plastics can improve universal value after broaden its function, but also conducive to
Environmental protection, is a promising flame retardants.
Cui Yan et al] studied the different flame retardants, different melt flow index of PP and PP flame retardant properties of inorganic fillers on the impact of
Ring, the results showed that those who make the melt flow performance degradation factors make PP flame retardant performance.
M double hydroxide composite metal oxide complex with APP, for polyamide 6/PP blends to produce good synergistic flame-retardant effect
Fruit. Metal catalyst to improve flame retardant effect of the flame retardant expanded applications. Mn and Zn compounds as
APP / pentaerythritol / PP catalyst intumescent flame retardant system, the other divalent metal ions can be generated in the APP intermolecular crosslinking
While releasing ammonia and H 2O. Four, PP flame retardant trends (a), halogen-free flame retardant and intumescent flame retardant
Currently, more commonly used non-halogenated flame retardants and inorganic flame retardants are intumescent flame retardant. Intumescent flame retardant is a new non-halogen flame retardant. Because of its low smoke when burned, and the generated gas discharge harmless carbon layer can effectively prevent the polymer droplet,
Suitable for PP flame retardant, so intumescent flame retardant research at home and abroad more and more attention, and has broad hair
Exhibition (two), triazine derivatives mainly nitrogen compounds
Triazine derivatives with a nitrogen-containing compound as an expansion-based flame retardant system in the  processing aid new charring agent, has been shown to provide
High intumescent flame retardant effect has significant synergies. It is halogen-free, low toxicity, high decomposition temperature, suitable for processing,
Little effect on the mechanical properties, no bleeding, excellent flame retardant properties, the starting material activity, can be a group with a compound containing different anti-
Should synthesize a variety of high melting point compounds. It is intumescent flame retardant system research and development focus.
(Three), inorganic flame retardants
Inorganic flame retardant non-toxic, non-corrosive, does not cause secondary pollution when burned, some better than organic flame retardant high temperature.
With the improvement of environmental requirements, but also the future development of inorganic flame retardants development of a trend. Especially for some flame retardant
Modified by [such as the use of silane coupling agent on the Al (OH) 3 surface modification] to improve flame retardant properties, has a broad development
Space.
(Four), polymer / flame retardant nanocomposites
(Five) synergistic flame retardant system
Synergistic flame retardant system combines the respective excellent performance, good effect, low cost, can be both flame and smoke suppression. It can be flame retardant compound, to reduce the flame retardants, the purpose of improving flame retardancy.
Six), other types of flame retardants
Enhanced dust-retardant (such as a halogen - antimony concentrated, capsule, wet body, etc.) of, reduce environmental pollution. The future development of non-dust flame retardants are one of the hotspots. In addition, high efficiency, low toxicity, low smoke and flame retardants and to improve compatibility with the base resin research is the development trend of flame retardants.