Magnesium Hydroxide Flame Retardant for PP
Sep 12, 2018

Polypropylene (PP) has outstanding advantages such as low density, good mechanical properties, chemical resistance, easy processing, high heat distortion temperature and low price. Flame retardant PP has become the flame retardant material with the highest flame retardant dose and the fastest growth.

Magnesium hydroxide flame retardant [Mg(OH) 2] as a halogen-free flame retardant, in addition to being flame retardant, it also has smoke suppression performance. Moreover, the dehydration temperature is high, and it is suitable for flame retardant modification of high polymer such as PP with high processing temperature. It can better meet the requirements of relevant laws and regulations in reducing environmental hazards and material safety treatment, and also make flame retardant plastics easier to recycle. In particular, magnesium hydroxide raw materials are abundant in source and low in price, and it is highly economical to use it as a flame retardant for PP, in recent years, all over the country have paid great attention to the use of Mg(OH) 2 flame retardant for PP. However, most companies currently use Mg(OH) 2 flame retardant for PP. Due to the insufficient amount of Mg(OH) 2, other flame retardants need to be added, resulting in high formulation costs.

Magnesium Hydroxide Flame Retardant for PP

When using magnesium hydroxide flame retardant for PP, in order to make the material reach UL94 V - 0 flame retardant grade ( 3. 2mm sample), the dosage should be more than 60%.But if you use Mg(OH) 2 as a smoke suppression, the dosage can be lower. The density of smoke of PP containing 40% Mg(OH) 2 is only about 1/3 of that of non flame retardant PP. When the content of Mg(OH) 2 in PP reaches 65%, its mechanical properties, especially impact strength and elongation, are significantly degraded.

In order to prevent the mechanical properties magnesium hydroxide flame retardant PP material from decreasing much, Mg(OH) 2 with fine particle size and narrow particle size distribution should be selected as raw material and need to surface modification treatment to improve the rheological properties of the material. It promotes the heat conduction of the surface of Mg(OH) 2 / PP during the mixing process to avoid the formation of local hot spots, and improves the compatibility of magnesium hydroxide with PP, so that it can be more uniformly dispersed in the polymer.

When this treated flame retardant magnesium hydroxide PP is used, good processing properties and physical and mechanical properties can be obtained even after the toughening modification of PP, even a flame retardant PP having a high Mg(OH) 2 content. In order to uniformly disperse Mg(OH) 2 in PP, the Buss kneader or German twin screw mixing extruder can be used. Or use a reciprocating single-screw kneading extruder for mixing, and use a reasonable feeding and mixing method.

For example, all of the PP material and toughening agent can be mixed with the required amount of 60% Mg(OH) 2 for the first time in the mixing and kneading machine for a few minutes, and then the remaining magnesium hydroxide is added for the second time. When feeding, it should be noted that the feeding should be uniform and the measurement should be accurate. If mixing with an internal mixer. It is necessary to add magnesium hydroxide twice, and accurately measure the charging rate in the range of 87%-93%. Inhomogeneous mixing not only reduces flame retardancy, but also lowers tensile strength and elongation at break, and the appearance of the product is also poor.

Top magnesium hydroxide have excellent compatibility, we can specify different solutions for different customers. More details please contact us:


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