Flame-retardant PP plastic profile materials are favored by more and more manufacturers due to their light density, excellent weather resistance and low overall price. In many applications, they have successfully replaced flame-retardant PS, flame-retardant ABS, etc. as the choice of plastic profile products. . Behind the rise of flame-retardant PP materials, there is a troublesome 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 causes mold scale, powdery agglomeration, mold sticking, etc. during the injection molding process, affecting normal production, but also often occurs in finished parts, producing white mist-like substances that affect the appearance of the product and lead to a decrease in flame retardancy. wait.

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

1. Compatibility of flame retardant and PP base material resin

Flame retardants are generally in two states in PP resin: one is filled in the resin in the form of a filler, and the other is evenly dispersed in the resin in a molten state. Since PP is a non-polar material, polar flame retardants and PP will have interface compatibility issues. The worse the interface compatibility, the more likely it is to cause precipitation problems.

2. Effect of temperature on flame retardant precipitation
PP plastic profile material is a semi-crystalline material with a low glass transition temperature. When the ambient temperature is higher than its glass transition temperature, as the temperature increases, the thermal movement of the amorphous chain segments will accelerate, causing the Small molecule flame retardants with poor compatibility with PP resin can easily overcome resistance and migrate to the surface.

This is also the reason why precipitation sometimes occurs on the surface of PP plastic profiles after being stored for a period of time. The high-temperature injection molding process is the most obvious process for precipitation. The precipitation is often reflected in mold scale on the mold. The higher the injection temperature, the more severe the precipitation. The relationship between the flame retardant migration rate and temperature can be roughly represented by Figure 4. Within the flame retardant decomposition temperature range, its precipitation rate accelerates significantly as the temperature increases. At constant temperature, precipitation is also related to time.

Solution to the precipitation of flame-retardant PP plastic profiles:

After understanding the causes of precipitation, we can improve the problem of flame retardant precipitation with twice the result with half the effort. There are two main methods:
1. Introducing strong polar groups (such as amine groups, carboxyl groups, epoxy groups, etc.) to enhance the interface between flame retardants and PP can effectively reduce the problem of flame retardant precipitation.

2. Increase the migration resistance between the flame retardant and the resin and reduce the migration rate of the low molecular weight flame retardant: lowering the temperature to weaken the movement between chain segments or increasing the polymerization degree of the flame retardant molecules and reducing the molecular weight distribution width will reduce the flame retardancy. Effective measures for agent precipitation.

It should be pointed out that the presence or absence of precipitation of flame retardant PP does not mean that there is no precipitation at all, it only greatly reduces the migration of the flame retardant. Current non-precipitation flame-retardant PP is often based on excessive technical costs. Therefore, low-cost anti-precipitation is still a topic that needs to be improved in current flame-retardant PP materials.