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Flame retardant dispersion performance impact of injection molding processing products

by:CSSSLD     2021-01-23
In the process of flame retardant PA manufacture, extrusion temperature on the injection molding processing and product performance has a great influence. Extrusion temperature is too low, the PA's molten plasticizing, flame retardant poor dispersion, product performance is uneven, extrusion temperature is too high, the decomposition of flame retardant, affect the product performance. So choose the appropriate extrusion temperature is very important. Select the principle of extrusion blending temperature in any of the following points: 1. For pure flame retardant PA, extrusion temperature adjustments should be near the PA melting point. 2. To enhance the flame retardant PA, extrusion temperature should be slightly higher than the melting point temperature. 3. To fill the influence of flame retardant PA performance for different PA base resin is not the same.

temperature and processing performance of PA itself has a certain relationship. Such as processing temperature of PA66 narrower, the effects of extrusion temperature relatively large. When determining the extrusion temperature, therefore, the best test to compare then determine the production process. High speed screw, the screw of the shear force is big, melting and mixing to produce positive effect for the material, unfavorable factors is to increase the high shear screw and material of friction, the friction between the screw and barrel, both friction produces a lot of heat, and even local overheating, that cause the material's thermal degradation.

the choosing principle of the screw rotation speed has the following points: 1. For flame retardant enhanced products, the screw rotation speed can be moderate, speed in 23. - 240. 2. For pure flame retardant PA should adopt a slightly higher speed. 3. Products for white or light color, low speed should be adopted. 4. For different nylon, the screw rotation speed has certain change, in general, for the high melting point to varieties, and high temperature should be adopted in the speed, to prevent the occurrence of the degradation reaction, for the variety of low melting point is not easy to decompose, can consider to low temperature high speed operation.

measures to improve the flame retardant dispersion degree: add right amount of dispersant, the appropriate mix process, make flame retardant and PA mixing, feeder should be equipped with a stirrer, guarantee the blanking separately; Appropriate improvement screw melting period of structure, which can guarantee the flame retardants and PA. Since PA is hygroscopic polymer, under the molten state, nylon prone to hydrolysis resulting in a loss of large molecules, resulting in reduced strength. So to make flame retardant PA, drying raw material easy to moisture absorption.

the screw rotation speed is accelerated, short staying time of material, does not favor the flame retardants and the mixture of PA, can make the product performance, when the screw rotation speed is too low, the material of shear force is insufficient, kneading and mixing effect is poorer, product performance, at the same time the material stay time is too long, can also cause the degradation of the material. Therefore, choosing the appropriate screw rotation speed is one of the important conditions of manufacture of high performance flame retardant PA.

also exists certain association between flame retardant effect. Such as bromine - Phosphorus, bromine - system Nitrogen and phosphorus - system Nitrogen system can produce very good flame retarding synergistic effect. MCA not only with phosphorus-containing flame retardant, bromine and antimony flame retardants have good association effect, but also can be used in combination with other additives, to obtain the very good flame retardant effect. Flame retardants of dispersion effect on product performance has two aspects, one is the effect of flame retardant, flame retardant scattered unevenly, will cause the flame retardancy of uneven, on the other hand is flame retardant scattered unevenly cause flame retardant PA impact strength uneven, particularly in flame retardant concentration will cause fracture first, can also lead to injection molding products processing surface layer falls off phenomenon.

the performance of the flame retardant PA PA resin molecular weight and size. Because of the adding amount of flame retardant, generally close to 20%, even more, small molecular compounds of add, reduce the performance of the PA, therefore, in order to ensure the performance of flame retardant PA to PA resin molecular weight to have certain requirements, the low relative molecular mass, the flame retardant PA low impact strength, high relative molecular mass, liquidity is poor, and the mixture of flame retardant effect is poor, also can affect its performance. So the relative molecular mass of the appropriate general is 18000 - 22000.

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