Foreword
Red phosphorus is extremely flammable – the main raw material for making matches. It seems incredible to use red phosphorus as a flame retardant, but red phosphorus is indeed an efficient flame retardant, especially when used in plastics; however, in resins, red phosphorus interacts with other phosphorus-containing flame retardants. The process is not simply oxidation. The phosphorus-containing flame retardant and the main GE flocculant must act in the condensed phase.
Flame retardant mechanism
①. Form phosphoric acid to act as a dehydrating agent and promote char formation. The formation of char reduces the heat conduction from the flame to the condensed phase and can play an insulating effect.
②. Phosphoric acid can absorb heat because it prevents CO from being oxidized into CO2 and reduces the heating process.
③. Form a thin glassy or liquid protective layer on the condensed phase, thereby reducing oxygen diffusion and heat and mass transfer between the gas phase and the solid phase, inhibiting the carbon oxidation process, and reducing the flammability substances and flammable gas concentrations.
④. The thermal decomposition of phosphorus-containing flame retardants undergoes the following changes: phosphorus-based flame retardants→phosphoric acid meta→phosphoric acid→polymetaphosphoric acid. Polymetaphosphoric acid is a stable compound that is not easily volatile and has strong dehydration properties. The compound is isolated from the air; the released water vapor absorbs a large amount of heat, causing the polymer surface flame retardant to thermally decompose and release volatile phosphide. Mass spectrometry analysis shows that the concentration of existing hydrogen atoms is greatly reduced, indicating that PO· can also capture H ·, that is, PO·+H·=HPO.
Introduction to phosphorus flame retardant system-halogen-free flame retardant series
Phosphorus flame retardants are a type of flame retardant that has a wide variety of uses and is equally important as halogen flame retardants. Phosphorus-based flame retardants have the advantages of low smoke and low toxicity. At the same time, they also have high flame retardant efficiency (especially in polymers containing oxygen or nitrogen). The flame retardant mechanism of phosphorus flame retardants can be divided into condensed phase and gas phase flame retardancy. In the condensed phase, the phosphorus-based flame retardant is thermally degraded to form phosphoric acid, which is further dehydrated by heat to form pyrophosphoric acid. Pyrophosphoric acid will form a protective layer on the polymer surface. At the same time, phosphoric acid and pyrophosphoric acid will promote dehydration and carbonization of the polymer surface to form a carbon layer, thereby achieving a flame retardant effect. In the gas phase, volatile phosphorus compounds or volatile phosphonium flame retardants formed by thermal decomposition of phosphorus-based flame retardants can capture active free radicals, thereby inhibiting the spread of flames.
Inorganic phosphorus flame retardant system
Inorganic phosphorus flame retardants mainly include red phosphorus, ammonium polyphosphate, phosphate, etc. Red phosphorus is a widely used flame retardant. Its main advantages are high flame retardant efficiency, low addition amount, smoke suppression and low toxicity. However, red phosphorus is easy to absorb moisture, oxidize, release PH3, dust, and has poor dispersibility. , easy to color the polymer. Therefore, red phosphorus is usually coated during use to form microencapsulated red phosphorus or called coated red phosphorus (MRP). According to literature reports, the coating layer can effectively inhibit the generation of PH3, reduce water absorption, and improve the autoignition point and thermal stability of red phosphorus. At the same time, its dispersion and flame retardant properties have also been improved and improved.
Organophosphorus flame retardant system
Organophosphorus flame retardants mainly include phosphates, phosphonates, phosphites, organic phosphonium salts, phosphine oxides and phosphorus-containing polyols. Among them, the most widely used ones are phosphates, phosphonates and phosphinic acid. Phosphate esters have both flame retardant and plasticizing functions. Bisphenol A bis(diphenylphosphate) (BDP) is a phosphate ester that has been produced and applied on a large scale. It is particularly effective in flame retardancy for oxygen-containing polymers.
Design plan for low-smoke halogen-free wire and cable products
1. Required regulations: The use of green and environmentally friendly materials is the development direction of exported wire and cable products. It is required that the material flame retardant system and all components in the material do not contain halogen elements such as F, Cl, Br, I, and heavy metals such as Cr, Cd, Hg, Pb, etc., pass RoHS, PAHs, REACH standards, and meet European and American, environmentally friendly, low-level Poison testing requirements;
2. Material selection: Use high-performance TPE/TPR to replace PVC and traditional vulcanized rubber. TPE/environmentally friendly hot melt adhesive TPR has soft touch, high elasticity, mild texture, adjustable surface gloss and fog brightness, low smoke, halogen-free, phosphorus-free, excellent oil resistance, weather resistance, aging resistance, flex resistance, ozone and chemical resistance etc. performance;
3. Processing and production: The extrusion line is fast and smooth. The waste generated during the production process (escaping burrs, extruded waste glue) and the final waste products are easy to recycle, reducing costs. Used TPE products can be simply regenerated and recycled, reducing environmental pollution and expanding the source of renewable resources. At the same time, the low specific gravity can reduce the volume cost of the product;
4. Scope of application: high-end headphone cables, data cables, video cables, medical cables, high-voltage cables, special wires and cables, outer quilt materials and plug materials, wire and cable sheaths, mobile phone charger wires, computer cables, Socket switches, USB cables, antennas, audio and video cables, game console cables, mouse cables, computer cables, connecting cables, submersible wires, wire connectors, and elastic flexible wires.
