Polypropylene (PP) has been widely used in many industries for its outstanding advantages of low density, good mechanical properties, chemical corrosion resistance, easy processing, high heat resistance and deformation temperature, and low price. Flame Retardant PP has become the largest flame retardant dose, the fastest growing polymer flame retardant materials. Magnesium hydroxide [Mg (OH) 2] as a kind of Halogen-Free Flame Retardant, besides can flame retardant and smoke elimination performance, and dehydration temperature is high, more suitable for PP, such as polymer flame retardant modification of processing temperature is higher, in reducing the harm to environment and processing in the material can meet the requirements of relevant laws and regulations, but also make the fire retardant plastic easier to recycle. In particular, Mg(OH)2 is rich in raw materials and low in price. It has high economic benefits as a flame retardant of PP. Therefore, Mg(OH)2 flame retardant PP is attached great importance to throughout the country in recent years.
However, when most enterprises use Mg(OH)2 flame retardant PP, due to insufficient Mg(OH)2 dosage, other flame retardants need to be added, resulting in high formula cost. Therefore, the author talks about some matters that should be paid attention to when Mg(OH)2 is used as PP flame retardant. When using Mg(OH)2 flame retardant PP, in order to make the material reach ul94V-0 flame retardant grade (3.2mm sample), the dosage should be ≥60%, however, if using Mg(OH)2 smoke suppression, the dosage can be lower, the smoke density of PP containing 40%Mg(OH)2 is only about 1/3 of that of non-flame retardant PP. When Mg(OH)2 content in PP reaches 65, its mechanical properties, especially its impact strength and elongation, deteriorate significantly. In order to reduce the mechanical properties of Mg(OH)2 flame retardant PP material, Mg(OH)2 with fine particle size, narrow and uniform particle size distribution should be selected as raw material and double-coupling surface treatment should be carried out to improve the rheological properties of the material and promote the formation of local hot spots through Mg(OH)2 / PP surface heat conduction during mixing processing. The compatibility of Mg(OH)2 with PP was improved, and Mg(OH)2 dispersed evenly in polymer.
When the treated Mg(OH)2 flame retardant PP is toughened and modified, even high Mg(OH)2 content flame retardant PP can obtain good machining performance and physical and mechanical properties. In order to disperse Mg(OH)2 evenly in PP, BussKenader, German twin screw extruder or reciprocating single screw extruder can be used for mixing, and reasonable feeding mixing and mixing method is adopted. For example, all PP and toughening agent with 60% Mg(OH)2 can be added to the mixer for the first time for several minutes and then the remaining Mg(OH)2 can be added for the second time.
When feeding, attention should be paid to uniform feeding and accurate measurement. If the dense mixer is used for mixing, Mg(OH)2 should be accurately measured in the range of 87% ~ 93% in addition to twice adding method. When the loading rate is small, the mixing effect is poor, when the loading rate > 95%, it is easy to cause Mg(OH)2 agglutination, difficult to disperse evenly. The uneven mixing not only reduces the flame retardancy, but also reduces the tensile strength and elongation at break, and the appearance of the products is poor. In conclusion, Mg(OH)2 can be evenly dispersed in PP by good toughening modification, special surface treatment and controlled particle size and size distribution of Mg(OH)2, suitable mixing machine and double feeding method. This kind of flame retardant PP can have mechanical properties and flame retardant properties of materials required in many application fields, but also has the characteristics of smoke suppression, low toxicity, halogen-free, no Sb2O3, environmentally friendly, low formula cost, and has higher economic and social benefits.
Novista Group supplies equivalent of FP-2100JC, FP-2200S, FP-2500S, Exolit OP1230, OP930, OP1312, OP1314 to global market.
