In order to reduce the cost, some fillers, such as calcium carbonate, barium sulfate and talcum powder, were added into the phosphorus nitrogen intumescent halogen-free flame retardant, and it was found that the flame retardant effect would be lost. Today, we will discuss the flame retardant mechanism and application of PP halogen-free phosphorus nitrogen intumescent flame retardant.
        1. Phosphorus nitrogen intumescent flame retardant consists of three parts.
        (1) Acid source: provide the acid for esterification reaction;
        (2) Carbon source: material providing hydroxyl or other groups needed for esterification reaction;
        (3) Gas source: provide the gas needed for expansion and foaming of the system.
        2. The flame retardant mechanism of phosphorus nitrogen intumescent flame retardant generally includes three parts
        They are carbon source (usually polyhydroxy compounds, such as pentaerythritol), acid source (such as ammonium polyphosphate, such as app) and foaming agent (such as melamine). They form carbon layer through the following interactions: 1, (2) at a temperature slightly higher than that of releasing acid, the acid reacts with the polyol (carbon source), and the amine in the system acts as the catalyst for the esterification reaction, (3) the system melts before or during the esterification reaction; (4) the water vapor produced during the reaction and the incombustible gas produced by the gas source make the system in the melting state expand and foam. At the same time, polyols and ester dehydration carbonization, forming inorganic and carbon residues, and further expansion of the system foaming; 5. When the reaction is close to completion, the system is gelatinized and solidified, forming porous foamed carbon layer.
        3. Why are some phosphorus nitrogen flame retardants easy to stick to water when they are extruded through the sink?
        The reason why the strips are easy to stick to water is that some components of the flame retardant have better water solubility. When passing through the screw machine outlet, the strips with higher temperature contact the cold water tank, and the powder is easy to precipitate, so the components in the flame retardant are difficult to dissolve in water.
        4. Why is there difference in flame retardant efficiency between different PP with the same fraction of flame retardant?
        Due to the different PP matrix, such as homopolymer PP and copolymer PP, due to the different olefin content in them, this is because there is PE side chain in copolymer PP, and the H atom in PP is more active than that in PE; the combustion heat of PP is lower than that of PE, and it works together with flame retardant at the beginning, and the decomposition temperature of PE is higher, and then it works; the decomposition temperature of PP substrate is between 227-247 ℃, while that of PE is between 335-450 ℃, and the flame retardant is less active When the decomposition temperature is 260 ℃, PP and flame retardant match better.
        5. Why is the effect of phosphorus nitrogen intumescent halogen-free flame retardant used in glass fiber PP worse?
        Generally speaking, with the decrease of PP content and the increase of flame retardant dosage, the flame retardant effect of the material will be better and better. Why the PP content in the glass fiber is relatively reduced (glass fiber is added), the number of flame retardant remains unchanged, but the flame retardant will become worse or even not flame retardant? This is mainly because the addition of glass fiber destroys the flame retardant mechanism of the phosphorus nitrogen expansion system, and the glass fiber is distributed in all parts of the plastic The closure of the layer has a great destructive effect, so that it can not isolate oxygen to achieve flame retardant effect.
        6. Why does phosphorus nitrogen intumescent halogen-free flame retardant lose its flame retardant effect after adding fillers or other substances?
        In order to reduce the cost, many people add some fillers, such as calcium carbonate, barium sulfate, talcum powder, magnesium hydroxide and so on, into the phosphorus nitrogen intumescent halogen-free flame retardant, and find that they will lose the flame retardant effect. The reason is that the addition of the above fillers changes the esterification reaction process, the acid source will react with the above fillers, and the above fillers destroy the formation of carbon layer on the surface of the material, leading to the failure of the mechanism.
        In the same way, adding some carbon black and toner will also lead to the loss of flame retardant effect. Therefore, some recycled PP materials may be partially filled with PP and added to the new materials, resulting in the above-mentioned fillers being added to the system in disguise, which makes the system lose its flame retardant effect.
        7. Why is there oil or powder precipitated on the surface of PP produced with some phosphorus nitrogen flame retardants after a period of time (several ten days)?
        As we mentioned, the flame retardant is composed of carbon source, acid source and gas source, and the one or more of the above substances must be precipitated. The water solubility is better, and the compatibility with plastics becomes poor. During processing, the material and the above powder are dispersed by the strong mechanical force of screw machine, and after a period of time, due to the continuous movement of molecules, the difference is obvious The above-mentioned powders gradually precipitate from the interior of the material to the surface.
        8. Why do some phosphorus nitrogen flame retardants appear foaming or graying in PP processing?
        Any flame retardant has its initial decomposition temperature, if the decomposition temperature of the flame retardant itself is only close to the melting temperature of the material, it is easy to appear the above situation. Therefore, generally speaking, the initial decomposition temperature of flame retardant should be at least 50 degrees higher than the temperature of material plasticization processing, so as to ensure the smooth processing. At the same time, the screw combination and processing conditions should be well controlled to avoid the actual temperature exceeding the initial decomposition temperature of flame retardant due to shear overheating inside the screw machine.