"White Frost" on The Surface of Flame-Retardant PP? Three Tricks To Solve It!

"White Frost" on the Surface of Flame-Retardant PP? Three Tricks to Solve It!

Flame-retardant PP materials have gradually become favored in fields such as electronic appliances, home appliances, and automotive in recent years, gradually replacing traditional materials like flame-retardant PS and flame-retardant ABS, thanks to their advantages of being lightweight, weather-resistant, and cost-effective.
Alongside the widespread application of flame-retardant PP materials, many users have reported issues: mold sticking during injection molding and "white frost" precipitating on the surface of finished products, which not only affects appearance but may also lead to performance degradation.

Yinsu, as a professional manufacturer in flame retardant R&D and production, tells you here: these problems are often closely related to the compatibility of the flame retardant and the processing temperature.

I. Why Does the Flame Retardant Precipitate?

1. Compatibility Issues
PP (polypropylene) is a non-polar material, while many flame retardants are polar. Their poor compatibility is like oil and water being difficult to mix. Over time, the flame retardant tends to gradually "separate out," forming precipitation.

2. The Influence of Temperature
PP is a semi-crystalline polymer with a relatively low glass transition temperature. When the ambient temperature rises, increased segmental motion of the molecular chains makes those poorly compatible, small-molecule flame retardants more likely to migrate to the product surface.
This is also why higher injection molding temperatures lead to more severe mold fouling, and why "white haze" can even appear on the product surface after storage for some time.

II. How to Effectively Inhibit Flame Retardant Precipitation?

1. Method 1: Enhance Interfacial Compatibility
Introduce strong polar groups (such as amine, carboxyl, epoxy groups, etc.) to improve the bonding force between the flame retardant and PP. This is like "building a bridge" between the two, reducing the tendency for separation.

2. Method 2: Reduce Migration Rate
Control temperature: Appropriately lower injection molding and storage temperatures to slow molecular movement.
Increase the degree of polymerization of the flame retardant: Use flame retardants with higher molecular weights and control the molecular weight distribution, thereby increasing migration resistance.

III. The Truth About "Non-Precipitating" Flame-Retardant PP
Currently, so-called "non-precipitating" flame-retardant PP on the market does not mean 100% zero precipitation. Instead, migration phenomena are significantly reduced through technical means. Unfortunately, such materials often come with higher costs.
Therefore, how to effectively inhibit precipitation while controlling costs remains a key challenge the industry needs to break through.

Conclusion
Although the precipitation problem in flame-retardant PP is common, it is not unsolvable. Through scientific analysis of the causes and targeted improvements, it is entirely possible to balance product performance and appearance. If you are also using flame-retardant PP materials, you might start from the two perspectives of compatibility and temperature, which could lead to better results with less effort.