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How to control the degree of polymerization when preparing Ammonium Polyphosphate (APP-1)?
This product is made of thermal phosphoric acid and ammonia as raw materials, and the degree of polymerization needs to be precisely controlled between 10-20. Put the phosphoric acid in a special steel reactor, and the reactor body needs to be glass-lined to prevent corrosion. When heated to 230℃, introduce ammonia gas through a copper pipe, and stir it with a stainless steel stirring paddle while passing it. The speed is maintained at 60 revolutions per minute to make the reaction uniform. When the pH value of the solution rises to 6.8, continue to react for 3 hours, take samples every half an hour during this period, and measure it with a viscometer. When the viscosity reaches 50 centipoise, stop heating immediately. At this time, the degree of polymerization is about 15, and Ammonium Polyphosphate (APP-1) is obtained. If the degree of polymerization is too low, less than 10, it will be too water-soluble and easily lost with rainwater when used for flame retardancy; if it is too high, more than 20, it will be difficult to dissolve in resin and particles will easily appear when mixed. The process is like controlling the length of a spinning line. If it is too short, it is easy to break, and if it is too long, it is difficult to weave. Only the one that is in the middle is suitable for most flame retardant scenarios. It is not only well compatible with the resin, but also can play the best performance when encountering fire.
What is the application of Ammonium Polyphosphate (APP-1) in polyurethane foam?
This product is an important material for polyurethane foam flame retardancy and can be used in both soft and hard foams. When used in soft foam, the addition amount is 18%, and it is mixed with polyether polyol and isocyanate through high-speed stirring. The catalyst effect is not interfered with during the foaming process. The pore structure is uniform and fine, and the pore diameter is maintained at 0.1-0.3 mm. The compressive strength is retained by 90% compared with those without addition. During the combustion test, the oxygen index increased from 21% to 30%, reaching the self-extinguishing level, and there was no molten dripping phenomenon, which can effectively prevent the spread of fire. Its decomposition temperature is about 250℃, which matches the degradation temperature of polyurethane foam. When it encounters fire, it decomposes before the foam, generates phosphate substances, catalyzes the carbonization of the foam surface, and forms a dense carbon layer with a thickness of about 2 mm, which can block the heat transfer to the inside. Compared with traditional brominated flame retardants, the smoke density released when it burns is 40% lower, and the toxic gas emissions are reduced by 30%. Therefore, it is widely used in foam products that are in close contact with people, such as furniture, mattresses, and car seats, which not only meet safety requirements, but also take into account health and environmental protection.
What are the characteristics of Ammonium Polyphosphate (APP-1) water solubility?
The solubility of this product is about 1.5g/100mL water at 25℃, which belongs to the category of low water solubility, so it is not easy to lose when used in a humid environment. Soak it in a normal temperature water tank for 72 hours, and regularly measure the phosphorus content in the aqueous solution. The calculated dissolution rate is about 5%, which is much lower than the 20% of highly water-soluble APP, so the products used outdoors are more durable. Its aqueous solution is weakly acidic, with a pH value of about 5.8. A small amount is applied to the surface of cold-rolled steel plates and observed after 30 days. The rust area is only one-fifth of that of highly water-soluble APP, and the anti-rust period is 2 times longer than the latter. Because of its moderate water solubility, it is easy to disperse in water-based coatings, and can form a stable suspension after high-speed shearing, and can be stored for a week without sedimentation; it is not easy to fail due to water contact. In the building exterior wall insulation material in rainy areas, the flame retardant performance remains 90% of the initial state after half a year of use. This feature makes it the preferred choice for use in multiple scenarios, whether indoor furniture or outdoor building materials.
What are the requirements for the synergy between Ammonium Polyphosphate (APP-1) and carbon source?
This product needs to be used in conjunction with a carbon source such as pentaerythritol, and the ratio of the two is preferably 3:1, supplemented with a small amount of melamine as a foaming agent to form a complete intumescent flame retardant system. In fire-retardant coatings, when encountering high temperatures, Ammonium Polyphosphate (APP-1) first decomposes to produce phosphoric acid, which acts as a dehydration catalyst to promote the dehydration of pentaerythritol into carbon. At the same time, melamine decomposes to release ammonia, causing the carbon layer to expand, and finally forming a honeycomb structure with a thickness of 15 times that of the original coating. If the carbon source ratio is too high, exceeding 1:1, the carbon layer will be loose and porous, like a sponge, and cannot effectively insulate; if it is too low, less than 1:4, the carbon content will be insufficient, and it will be difficult to form a complete protective layer, and the fire will easily break through and spread. When used in conjunction with melamine, the amount added is one-third of APP-1, which can increase the expansion height of the carbon layer by another 30%, with better porosity and improved thermal insulation performance. According to tests, the substrate temperature can be kept below 180℃ within 1 hour in a fire. Its synergy is like the king and his ministers, APP-1 is the commander, coordinating catalysis, the carbon source is the phase, building a defense line, and the foaming agent is the general, helping expansion. The three perform their respective duties to achieve the best flame retardant effect.
What are the special requirements for the storage of Ammonium Polyphosphate (APP-1)?
This product needs to be packaged in polypropylene woven bags with a bag thickness of not less than 0.12 mm, lined with polyethylene film with a film thickness of 0.08 mm, 25 kg per bag, and the bag mouth is heat-sealed with a width of not less than 10 mm to ensure tightness. It is stored in a ventilated warehouse with a concrete structure. The warehouse needs to be installed with an axial flow fan, ventilated for 2 hours a day, and the relative humidity is strictly controlled below 60%. The temperature does not exceed 30℃. A 3 cm thick wooden board is laid on the ground to keep the material 30 cm off the ground, and a layer of moisture-proof oil paper is laid on the top of the wooden board. When stacking, the "well" shape is used, with 4 bags per layer, and the stack height does not exceed 8 layers. The distance between the stacks is kept at 50 cm for easy ventilation and handling. If the humidity of the storage environment is too high, exceeding 70%, the surface is easy to absorb moisture and form lumps with a diameter of no more than 5 cm. However, it can still be used after being gently tapped and crushed by a wooden hammer, and the performance is not reduced. It needs to be stored separately from alkaline substances such as sodium hydroxide and lime, with a distance of not less than 2 meters to prevent contact with ammonia and produce pungent odor. It needs to be covered with rainproof tarpaulin during transportation, with a tarpaulin coverage rate of 100%. It needs to be stopped in rainy days to avoid rain. After unloading, check whether the packaging is damaged. If it is damp, it needs to be spread out in a cool and ventilated place to dry for 24 hours to keep it dry and loose, so as to facilitate subsequent uniform mixing with other materials.