Flame retardant modified graphene superconducting sheet production line of Polyoxymethylene
DATE：2021/6/22 8:39:10 / READ： / SOURCE：This station
Flame retardant modified graphene superconducting sheet production line of Polyoxymethylene
POM is a kind of engineering plastics with excellent comprehensive properties. It has the advantages of high hardness, good wear resistance, fatigue resistance, high chemical stability, outstanding solvent resistance, good electrical insulation, low water absorption and good dimensional stability of products. It can be used to replace non-ferrous metals and their alloys, and is widely used in automobile, electronic and electrical, various precision machinery, electronic equipment, etc Hardware and building materials industry. In addition, its raw materials are cheap and easy to get, forming and processing is convenient, and its consumption has maintained a sustained growth momentum. With the increasing application of POM, the requirement of flame retardant modification is more and more strong, so it is necessary to develop high-efficiency flame retardant and flame retardant POM. The OI of POM is the lowest among all the polymer materials (only 15.0%) because POM is a kind of highly combustible polymer material; In addition, POM has strict requirements on flame retardants in the process of molding. A small amount of flame retardants will cause a large amount of decomposition of POM. In addition, because POM is a high crystalline polymer, adding a large number of additives or other polymer materials will greatly reduce its physical and mechanical properties, especially the weak notched impact properties, so the flame retardancy of POM is quite difficult. Graphene superconducting sheet production line www.handern.comMg (OH) and app can be used as flame retardants of POM. When Mg (OH) is added, the flame retardancy of POM is greatly improved; When the mass fraction is 60%, the oxygen index increases from 15 to 40, and the horizontal combustion rate decreases from 0.33mm/s to 0.31mm/s. The flame retardant effect of app is better than that of Mg (OH): when the dosage of APP reaches 25%, the self extinguishing POM can be obtained. The mechanical properties of POM decreased with the addition of both flame retardants. At the combustion temperature of POM, Mg (OH) 2 can decompose and release water, absorb the heat generated by combustion, reduce the combustion speed of materials, and even completely prevent combustion. With the increase of Mg (OH) 2 addition, the limiting oxygen index (LOI) of POM / Mg (OH) system increases gradually, especially when the Mg (OH) Z addition reaches 40%. When the dosage of Mg (OH) 2 was 60%, the OI of POM / Mg (OH) 2 system increased from 15% to 40%. When adding a small amount of Mg (OH) 2, the horizontal combustion rate of the system does not decrease, but increases to a certain extent. When the addition of Mg (OH) 2 reached 40%, the horizontal combustion rate of the system gradually decreased. Due to the poor compatibility between POM and inorganic flame retardant Mg (OH) 2, the mechanical properties of the system decreased after adding Mg (OH) 2. In order to improve the mechanical properties of POM / Mg (OH): system, Mg (OH) 2 is usually surface treated to improve its compatibility with POM, so as to reduce the adverse effect of Mg (OH): on the mechanical properties of POM. Stearic acid and KH550 are better treatment agents for Mg (OH). Mg(OH); The horizontal burning rate of the system decreases gradually when the dosage reaches 40. POM and inorganic flame retardant me (OH); The mechanical properties of the system decreased after adding Mg (OH). In order to improve the mechanical properties of POM / me (OH): system, the surface of M (OH) is usually treated to improve its compatibility with POM, so as to reduce the adverse effect of Mg (OH): on the mechanical properties of POM. Stearic acid and kh50 are Mg (OH); It is a better treatment agent. Graphene superconducting sheet production line www.handern.com
App is an important phosphorus inorganic flame retardant developed rapidly abroad in recent ten years. It is widely used in plastic industry abroad for its excellent performance. App is close to the neutral pH value, which avoids the "zipper" reaction of general phosphate to POM. During the combustion process of app, the acid is released as a strong dehydrating agent, which promotes the water to be separated from the oxygen-containing polymer to form a coke film, which blocks the heat conduction and oxygen entering, and effectively delays and prevents the thermal degradation of the polymer; The matrix was isolated and the production of volatile free formaldehyde was inhibited. At the same time, the ammonia produced by decomposition reduces the concentration of formaldehyde vapor, reduces the flame temperature and takes away part of the heat, so as to achieve the purpose of flame retardant. It can be seen from table 6-21 that with the increase of APP addition amount. The oxygen index of POM / APP blends increased. When adding a small amount of app into POM, the horizontal combustion rate does not decrease, but increases to a certain extent. When the app content reaches 25%, the spline will be extinguished quickly after enough time of ignition in the test process and the fire source is removed. Graphene superconducting sheet production line www.handern.com
The most suitable flame retardants for POM are melamine, app and melamine salt of pentaerythritol diphosphate (MPP). Adding 30 parts of the mixture of app and MPP and 20 parts of melamine to 100 parts of POM can make the oxygen index of flame retardant POM reach 49; Adding 30 parts of the mixture of app and MPP, 20 parts of melamine and 10 parts of formaldehyde absorbents into 100 parts of POM can make the oxygen index of flame retardant POM reach 50, the vertical combustion is higher than FV-0, and the mechanical properties of both are reduced by less than 50%. When adding common flame retardants such as tris (a-chloropropyl) phosphate, dichloropropyl dihydrophosphate or chlorinated paraffin with antimony trioxide, the combustion rate of POM is faster, which is believed to be due to the decomposition of POM to release free formaldehyde through the "zipper" effect of phosphoric acid or halogen groups. This free formaldehyde is highly combustible. It can destroy the equilibrium of flame self extinguishing reaction caused by flame retardant. Strong basic compounds can also promote the release of methyl bromide by cleaving the acyl end group of POM chain. Flame retardant modification of POM is to add flame retardant to improve the cracking process of POM, in other words, to reduce the relative amount of formaldehyde emitted by zipper reaction or other reactions through competitive reaction, and to increase the amount of non combustible carbon dioxide, water vapor, other non combustible gases and free carbon. Even when the concentration of these gases is too small to make their mixture with formaldehyde not small, these gases will improve the combustion reaction of formaldehyde, giving a large, yellow flame instead of a compact blue flame. This reduces the rate of heat transfer to the solid polymer and thus the heat required to break more of the polymer into volatile combustible products. The formation of carbon layer on the polymer surface can further act as a heat transfer barrier, and also reduce the release rate of volatile combustible products supplied to the flame. Graphene superconducting sheet production line www.handern.com
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