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ADDITIVES | FLAME RETARDANTS


Figure 4: Huber Martinswerk partnered with Buss, Exxon- Mobil and Evonik to develop a silane cross-linkable cable formulation based on Martinal OL-104 LEO and Martinal OL-107 LEO to meet the new CPR class B2 classification


Flame Spread [mm] 1640 THR 1200s [MJ] PHRR [kW] FIGRA [W/s] 18.5 30.3 77.9 Source: Huber Martinswerk


60% Martinal 65% Martinal Requirement 1040


10.2 17.,7 50.3


1500 mm Class B 2000 mm Class C


15 MJ Class B 30 MJ Class C


30 kW Class B 60 kW Class C


120 W/s Class B 300 W/s Class C


Figure 5: Increasing the Magnifin H5 HFFR loading level improves FR performance (measured by heat release rate) and char strength, but at the expense of mechanical properties and processing Source: Huber


which it markets as Firebrake. Zinc borates can function as flame retardants,


smoke suppressants, afterglow suppressants, and anti-tacking/arcing agents. They can be used in a range of polymer systems, including PVC, polyam- ides, epoxy, polyolefins, polyurethane, and various rubbers. Rio Tinto claims that a considerable amount of halogen-free formulations involve the use of borates in various forms such as zinc borate, ammo- nium pentaborate, boron phosphate, melamine borate, boric acid, sodium borate, and others. The company also says the manufacturing process used by its Twenty Mule Team Borax operation generates virtually no waste. This is a key advantage as two major zinc borate producers in China have been forced to close over environmental concerns. Kisuma5 is the brand name for a range of highly


pure Mg(OH) 2 FRs from Kyowa Chemical Indus- try. Mg(OH) 2


at temperatures above 340°C, resulting in the 42 COMPOUNDING WORLD | December 2017 starts decomposing endothermically


formation of magnesium oxide (MgO) and water. The water results in cooling and decreased pyrolysis of the polymer, at the same time diluting the fuel/oxygen ratio while the MgO works as a protective layer to provide a smoke suppressant effect. The supplier claims that, due to its high decom- position temperature, Kisuma5 is generally considered the best in its kind for high tempera- ture, halogen-free applications. The range com- prises grades with different surface coatings to fit specific industry needs. Kisuma5A, for example, is a standard grade, Kisuma5B provides improved low temperature flexibility and mechanicals, Kisuma5B- 1G improves processability and mechanicals, Kisuma5J provides what Kyowa says is “extraordi- nary” water and acid resistivity and wet electrical properties, Kisuma5L is designed for better tensile and high heat stability, and Kisuma5C is uncoated. Mineral-based FR supplier Huber Martinswerk, highlights the importance of these types of FRs in building and construction applications, especially those that fall within the restriction of the Euro- pean Union’s Construction Products Regulation (CPR). The company offers a wide range of HFFRs for use in thermoplastic and cross-linkable wire and cable applications, which meet CPR fire classes (B2, C, D and E). For example, improved HFFR performance in cable insulation and sheath- ing can be obtained by increasing the loading level of a fine precipitated 4m2


/g ATH product,


Martinal OL-104 LEO (Figure 4). Further improve- ments in HFFR performance can be obtained by incorporating Martinal LEO products with higher specific surface areas, such as OL-107 LEO (7 m2


/g) and OL-111 LE (11 m2 /g). To achieve higher thermal stability under


increased cable extrusion line speed or for thermo- plastic polymers having a higher melting point, HFFR wire and cable compounds can include synthetic high-performing magnesium hydroxides such as Huber Martinswerk’s Magnifin product portfolio (Figure 5).


Mineral synergists Nabaltec has developed a new mineral-based masterbatch, Apyral AOH EXL 500-17-C, which it claims is a highly efficient flame retardant synergist for ATH. The product in powder form can be easily blended with mineral fillers and is highly compat- ible with an extensive variety of polymers, the supplier says. At addition levels of only 4wt%, the additive is said to improve fire retardancy signifi- cantly compared to ATH on its own. In an LLDPE/EVA formulation, the combination


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