Several typical flame retardant mechanism in flame retardant

Several typical flame retardant mechanism in flame retardant

1. The development of phosphorus and nitrogen-based intumescent flame retardants is dynamic.

Expansion-type flame retardants generally phosphorus, nitrogen as the main component, does not contain halogen, and does not use antimony oxide as a co-effector. When the polymer containing such flame retardants is heated, the surface can generate a uniform layer of carbon foam, which plays the role of heat insulation, oxygen barrier, smoke suppression, and prevents the phenomenon of molten droplets, and has good flame retardant properties. Expandable flame retardants meet today's demand for flame retardants less smoke, low toxicity of the development trend, is considered to be one of the promising ways to achieve halogen-free flame retardants. Intumescent flame retardants are mixed expansion type and single-component expansion type. Mixed expansion type flame retardant is due to individual acid source (such as phosphate or phosphate), carbon source (such as polyol) and gas source (such as nitrogen-containing compounds) composed of a mixture. Suitable for flame retardant PE and PP, when the amount of 25%-30%, flame retardant materials oxygen index up to 30, flame retardant level up to UL94V0 class. Ammonium polyphosphate based intumescent flame retardants are the current research hotspots. Greatly superior to many small molecule flame retardants, may become a new generation of products in the future.

2. surface modification, ultra-fine is the development direction of inorganic flame retardants

Inorganic flame retardants have good thermal stability, non-volatile, non-corrosive and toxic gases, etc., and inexpensive, inorganic flame retardants account for more than half of all types of flame retardants. The main varieties are: aluminum hydroxide, magnesium hydroxide, red phosphorus, antimony oxide, molybdenum oxide, zirconium oxide, ammonium molybdate, zinc borate, etc., of which aluminum hydroxide (ATH) accounts for more than 80% of inorganic flame retardants. However, due to the poor flame retardant effect of inorganic flame retardants and the large amount added, new technologies such as ultra-fine, surface modification and macromolecular bonding must be used to improve them.

3. Surface modification Inorganic flame retardants have strong polarity and hydrophilicity, and are not compatible with non-polar polyurethane.

Inorganic flame retardants have strong polarity and hydrophilicity, and are not compatible with non-polar polymers. In order to improve the adhesion and interfacial affinity between them and the polymer, the use of coupling agents for its surface treatment is one of the most effective methods. Commonly used coupling agents are silane and titanate. ATH treated with silane, such as good flame retardant effect, can be extremely effective in improving the bending strength of polyester and epoxy resin tensile strength; ATH treated with ethylene silane, can be used to improve the cross-linked ethylene vinyl acetate copolymer flame retardancy, heat resistance and moisture resistance. Titanate coupling agents and silane coupling agents can be used together to produce synergistic effects. After surface modification, the surface activity of ATH is improved, the affinity with resin is increased, the physical and mechanical properties of products are improved, the processing fluidity of resin is increased, the moisture absorption rate of ATH surface is reduced, the electrical properties of flame retardant products are improved, and the flame retardant effect can be improved from V 1 to V 0.

4. Ultra-fine At present, the main research and development direction is the ultra-fine and nano-fine of ATH.

The addition of large amounts of ATH will reduce the mechanical properties of the material, but the use of ultra-fine, especially nano-level ATH filled plastic, will have the effect of rigid particles plasticization and enhancement. This is because the flame retardant effect is governed by the chemical reaction, for the same amount of flame retardant, the smaller the particle size, the larger the specific surface area, the better the flame retardant effect. On the other hand, ultra-fine, nano ATH, enhanced interfacial interaction, can be more uniformly dispersed in the matrix resin, more effective in improving the mechanical properties of the blend. For example, if LDPE/EVA (70/30) is filled with ATH of 10μm particle size developed by Solem, the extrusion capacity can be increased by 40%.

5. Smoke elimination technology

In a fire, smoke is the first and most deadly and delayed fire fighting factors, so the contemporary "flame retardant" is compared with "smoke suppression", and for some plastics, such as PVC, "smoke suppression " than "flame retardant" is more important. Halogen-containing polymers, halogenated flame retardants and antimony compounds are the main sources of smoke generation. Therefore, in addition to the non-halogenation of flame retardants is the main way to reduce the amount of smoke, PVC and other halogen-containing polymers using the addition of smoke suppressants is the way to solve the smoke.

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