Analysis and solution of the precipitability of th

2022-07-31
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Analysis and solutions to the precipitation problem of flame retardant PP materials

flame retardant PP materials have been favored by more and more manufacturers because of their lightweight density, excellent weather resistance and low comprehensive price. They have successfully replaced flame retardant PS and flame retardant ABS in many applications. Behind the rise of flame retardant PP materials, there is a perplexing problem that may often be encountered, that is, the precipitation of flame retardant materials, which is more obvious in halogen-free flame retardant materials

the release of flame retardant not only often produces mold scale, powdery caking, mold sticking, etc. in the injection molding process, but also often occurs in the finished products, resulting in white mist substances, which affect the appearance of the products and lead to the decline of flame retardancy

before solving the problem of flame retardant precipitation, we first discuss two important factors affecting the problem:

first, the compatibility between flame retardant and PP base resin

flame retardant generally has two states in PP resin: filling the resin in the form of similar filler, and the other is uniformly dispersed in the resin in the form of melting. As PP is a non-polar material, the "lifting" of very recent flame retardant and pled lighting brings opportunities to the heat dissipation material market, and P will have interface compatibility problems. The worse the interfacial compatibility is, the easier the precipitation problem will occur

II. Effect of temperature on the precipitation of flame retardant

pp is a semi crystalline substance with low glass transition temperature. When the ambient temperature is higher than its glass transition temperature, the thermal movement of amorphous chain segment will accelerate with the increase of temperature, so that the small molecule flame retardant with poor compatibility with PP resin can easily overcome the resistance to migrate to the surface

this is also the reason why precipitation sometimes occurs on the surface of parts after they are stored for a period of time. The precipitation is most obvious in the high-temperature injection process, which is often reflected in the formation of mold scale on the mold. The higher the injection temperature, the more severe the precipitation. The relationship between flame retardant migration rate and temperature can be roughly shown in Figure 4. Within the range of flame retardant decomposition temperature, the precipitation rate increases significantly with the increase of temperature. At constant temperature, the precipitation is also related to time

after understanding the cause of precipitation, the improvement of flame retardant precipitation can get twice the result with half the effort. There are two main methods:

scheme:

1 Introducing strong polar groups (such as amino group, carboxyl group, epoxy group, etc.) to enhance the interface between flame retardant and PP can effectively reduce the problem of flame retardant precipitation

2. Increasing the migration resistance between flame retardant and resin and reducing the migration rate of low molecular weight flame retardant: reducing the temperature to weaken the movement between chain segments or improving the polymerization degree of flame retardant molecules and reducing the molecular weight distribution width become effective measures to reduce the precipitation of flame retardant

it should be pointed out that zhuneizhang said that the precipitation free flame retardant PP is not completely free of precipitation, but only reduces the mobility of flame retardant to a great extent. The current non precipitation flame retardant PP is often based on the high technical cost, so the low-cost anti precipitation is still a subject that needs to be improved for the current flame retardant PP materials

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