Shanghai Risheng Technology Co., Ltd.

Flame retardant PP material because of its light density, excellent weather resistance and comprehensive low price, by more and more manufacturers of all ages, in many applications has successfully replaced the flame retardant PS, flame retardant ABS and so on. Behind the rise of flame retardant PP materials, there is a perplexing problem that may often be encountered, that is, the problem of precipitation of flame retardant materials, which is more obvious in halogen-free flame retardant materials. Flame retardant precipitation not only often occurs in the injection molding process to produce mold scale, powder agglomeration, adhesive mold and other effects affect the normal production, in the finished products also often occur in precipitation, resulting in white mist substances affect the appearance of products and lead to flame resistance decline.

Before solving the problem of flame retardant precipitation, we first discuss two important factors that affect the precipitation problem:

Compatibility of 1. Flame Retardant with PP Base Resin

Flame retardants are generally in two states in PP resins: filling the resin in the form of similar fillers, and the other is uniformly dispersed in the resin in a melted state. Because PP is a non-polar material, polar flame retardants and PP will have interfacial compatibility problems. The worse the interfacial compatibility is, the easier it is to cause the problem of precipitation. Therefore, the introduction of strong polar groups (such as amine groups, carboxyl groups, epoxy groups, etc.) to enhance the interface between flame retardant and PP can effectively reduce the problem of flame retardant precipitation.

Effect of 2. Temperature on Precipitation of Flame Retardant

PP is a semi-crystalline material with a low glass transition temperature, when the ambient temperature is higher than its glass transition temperature, with the increase of temperature, the thermal movement of amorphous chain segments will accelerate, making it easier for small molecule flame retardants with poor compatibility with PP resins to overcome resistance to migrate to the surface. This is also the reason why the surface of the parts is sometimes precipitated after being stored for a period of time. The high-temperature injection molding process is the most obvious process of precipitation, which is often reflected in the mold scale, etc. The higher the injection temperature, the more severe the precipitation.

The relationship between flame retardant migration rate and temperature can be roughly shown in the following figure. In the range of flame retardant decomposition temperature, the precipitation rate is obviously accelerated with the increase of temperature. At constant temperature, precipitation is also related to time.

Therefore, in order to reduce the precipitation of flame retardant, it is necessary to improve the migration resistance between flame retardant and resin and reduce the migration rate of low molecular weight flame retardant. Reducing the temperature to weaken the movement between chain segments or improve the degree of polymerization of flame retardant molecules and reduce the width of molecular weight distribution has become an effective measure to reduce the precipitation of flame retardants.

After understanding the causes of precipitation, the improvement of flame retardant precipitation can be twice the result with half the effort. Plastic Yi'an TM series is a typical representative of precipitation-resistant flame retardant materials.

In general, in order to make flame retardant PP material have better flame retardancy, its melt index is generally not too high (less than 20g/10min,230 ℃ * 2.16kg), and the higher the melt index, the easier it is to drip and the more difficult it is to reach V0 level. Plastic Yian TM high-flow halogen-free flame-retardant PP series represents brand HFP1010-05, has excellent wide-range processing conditions (normal processing temperature can reach 240 ℃, no precipitation), excellent flame-retardant 1.6mm V0 grade, improves the processing condition limit of flame-retardant parts, and greatly expands the application of large-scale flame-retardant parts. At present, the technology has obtained the national invention patent (Patent No. 201210233346.7).

It should be pointed out that the non-precipitated flame retardant PP is not completely precipitated, it only greatly reduces the migration of the flame retardant. The current non-precipitation flame retardant PP is often based on high technical costs, so low-cost anti-precipitation is still a subject that the current flame retardant PP material needs to be perfected.