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Why does Ammonium Polyphosphate (APP-2) need high temperature treatment during preparation?
This product needs to be made through ultra-high temperature polymerization process, otherwise the required performance cannot be obtained. Phosphoric acid and ammonia are put into a high temperature resistant nickel-chromium alloy reactor in proportion, and the reactor body can withstand high temperature and high pressure above 300℃. First, heat the phosphoric acid to 200℃ for preheating, and then gradually increase the temperature to 280℃, which is 50℃ higher than the reaction temperature of APP-1. When ammonia is introduced, the pressure is controlled at 0.3MPa to enhance the reaction intensity. A special ceramic stirring paddle is used to stir while passing. The paddle is wear-resistant and does not react with the material. The reaction lasts for 5 hours, during which the molecular chain length is monitored by infrared spectroscopy. When the degree of polymerization reaches 20-30, the reaction is stopped, and the material is discharged after the temperature drops to 100℃ naturally. This high-temperature process is like forging iron into steel. Only after being tempered by intense fire can a strong chain be obtained, making the molecular structure more stable. Therefore, its thermal stability is far superior to APP-1. It does not decompose below 280℃, and can still maintain its original structure even in a processing environment of 260℃. For this reason, it is suitable for engineering plastics that are processed at high temperatures, such as polyamide and polyester. The processing temperature of these materials often reaches about 250℃. Ordinary APP has begun to decompose at this temperature, while Ammonium Polyphosphate (APP-2) can exist stably to ensure that the flame retardant effect is not affected.
What are the advantages of Ammonium Polyphosphate (APP-2) in engineering plastics?
This product has significant advantages in the application of engineering plastics, especially for high-temperature processing materials such as polyamide and polybutylene terephthalate. When added to polyamide 6 plastic, the dosage is 20%, mixed by a twin-screw extruder, and there is no decomposition at a processing temperature of 250℃. The plastic particles produced are white in color and do not turn yellow. The combustion test reaches UL94 V-0 level, and the heat deformation temperature is retained at 85%, which can still meet the requirements of high temperature resistance in engineering use. When used in polybutylene terephthalate, it is used in combination with glass fiber, and the addition amount of 15% can reach the flame retardant standard. At the same time, the tensile strength of the material is still above 100MPa, the bending modulus is maintained at 3.5GPa, and the mechanical performance loss is small. Due to the high degree of polymerization and long molecular chain, it has strong entanglement with the polymer resin chain and is not easy to migrate. After 100 hot and cold cycle tests, it switches repeatedly from -40℃ to 80℃, and there is no frost on the plastic surface, which remains smooth. The surface of its particles is treated with silane coupling agent, which is tightly bonded to the resin interface, so that the impact resistance of the material is improved by 15%, and the notched impact strength reaches 5kJ/m², which is more durable than the untreated ones. Therefore, it is widely used in engineering plastic products with high strength requirements such as automotive parts and electronic and electrical housings.
What are the differences between the physical properties of Ammonium Polyphosphate (APP-2) and APP-1?
Ammonium Polyphosphate (APP-2) is a white powder with regular particle shape, mostly spherical, slightly larger particle size, about 50μm. The particle size distribution range is narrow, and 90% of the particles are between 40-60μm, measured by a laser particle size analyzer. It is easier to disperse in coarse particle resins, such as reinforced plastics filled with glass fiber, than APP-1's 30μm, and is not easy to agglomerate when mixed. Its density is 1.7g/cm³, slightly higher than APP-1's 1.6g/cm³, so it settles slowly when filled in plastics, and is not easy to stratify during storage, so that the uniformity of the material is maintained longer. It has lower water solubility, with a solubility of only 0.5g/100mL water at 25℃. When it is immersed in room temperature water for 72 hours, the dissolution rate is about 1.5%, which is much lower than APP-1's 5%. It has better stability in humid and hot environments, such as the rainy season in the south. When used for outdoor products, the loss of flame retardant components is very small. The thermal decomposition temperature is 290℃, which is 40℃ higher than APP-1's 250℃. Through thermogravimetric analysis, in a nitrogen atmosphere, the 5% weight loss temperature is 290℃, while APP-1 is 250℃. Therefore, it can withstand high-temperature processing of engineering plastics. For example, polyamide does not decompose at an injection molding temperature of 260℃, and does not produce toxic gases to pollute the environment, nor does it affect the mechanical properties of plastics.
How to use Ammonium Polyphosphate (APP-2) in cable materials?
When Ammonium Polyphosphate (APP-2) is used in cable materials, it needs to be coordinated with components such as polyvinyl chloride resin, plasticizer, and stabilizer. According to the formula ratio, the addition amount is 22%, supplemented with 10% magnesium hydroxide, and premixed in a high-speed mixer for 10 minutes at a speed of 1500 rpm to disperse the components initially, and then put into a twin-screw extruder for granulation. The extrusion temperature is controlled at 160-180℃ and the screw speed is 300 rpm to ensure that the materials are fully melted and mixed. The particles are evenly dispersed in the cable material, and there are no particles visible to the naked eye. The oxygen index of the prepared cable material reaches 32%, far exceeding the 20% without addition. The self-extinguishing time in the vertical combustion test is less than 10s, which meets the cable flame retardant standard. During the processing, due to good thermal stability, non-stick screw and die head, smooth extrusion surface, no pores and coke particles, and reduced scrap rate. The manufactured cable has been subjected to an aging test at 80℃ for 1000 hours, and the flame retardant performance has not attenuated, the oxygen index remains above 31%, and the dielectric constant is stable. The dielectric constant is 3.5 at a frequency of 1MHz, which is similar to that without addition, and does not affect the insulation performance of the cable. It has good compatibility with plasticizers, which keeps the cable material soft, and the elongation at break is greater than 200% at room temperature. It still has good flexibility at low temperature of -20℃, and is not easy to crack. It is suitable for cable laying under various climatic conditions.
What is the difference between Ammonium Polyphosphate (APP-2) and APP-1 in terms of cost and applicable scenarios?
Due to the complex preparation process, Ammonium Polyphosphate (APP-2) requires ultra-high temperature polymerization, a long reaction time of 5 hours, large equipment loss, and slightly low raw material utilization, so the cost is about 15% higher than APP-1. Through production cost accounting, the production cost of APP-2 per ton is about 2,000 yuan higher than that of APP-1, but its performance is better and it is suitable for high-end engineering plastics and high-temperature resistant products. In scenes with strict flame retardant requirements, such as automobile engine peripheral parts and electronic component housings, these parts are often in high temperature environments and need to withstand temperatures above 200°C. APP-2 must be used to ensure a lasting flame retardant effect; while APP-1 has a lower cost and is suitable for scenes such as ordinary plastics and coatings, such as polyurethane foam for indoor furniture and building insulation materials. These scenes do not require high processing temperatures and are highly cost sensitive. Using APP-1 can control costs while meeting basic flame retardant requirements. The two are like fine and coarse cloth. The fine APP-2 has a fine weaving process and is suitable for Chinese clothes, that is, high-end precision products; the coarse APP-1 has a practical texture and is suitable for daily wear, that is, popular products. Each is used according to needs to balance performance and cost.