FLAME RETARDANTS | INNOVATION
via char formation. The protective layer of char provides a heat-insulation effect, reduces oxygen access, and prevents dripping of molten polymer. “Furthermore, the potential to reduce overall filler content will result in better physical properties of the jacketing compound,” Huber says. Kemgard smoke suppressants comprise molyb-
Above: The cable industry is a key market for halogen- free flame retardant solutions, with increasingly demanding standards
being imposed
it is in the process of introducing a new Safire nitrogen-phosphorus fire retardant technology. Secondly, it has also provided new data for its Kemgard smoke suppressants for use in flexible and rigid PVC. And thirdly, the company’s Martinal OL-104 LEO precipitated ATH — originally devel- oped in Germany by Huber Fire Retardant Addi- tives business Martinswerk — has now been available in North America from the company’s plant at Bauxite, South Arkansas. Huber says Safire 400 melamine poly(zinc
phosphate) “imparts an enhanced balance of flame retardancy, smoke suppression and char formation. It has been designed to catalyse the formation of a strong glassy char layer in most thermoplastics. In addition, the presence of zinc further reduces smoke production and helps suppress arc track values when required.” In recent studies, the company says Safire 400 has been shown to be a highly efficient synergist with aluminium hydroxide in LSZH (low smoke zero halogen) cable formulations. Partial replacement of AlOH reduces the rate of polymer decomposition
dates precipitated on a functional core material to maximise the active surface area. Depending on the material, the core can offer secondary benefits such as additional fire retardancy or improved process- ability. The molybdate chemistry is designed to catalyse crosslinking in the PVC matrix, leading to improved organic char formation.
Cable demands Germany’s Nabaltec says that polyolefin com- pounds highly filled with aluminium hydroxide (ATH), which it sells as Apyral, or magnesium hydroxide (MDH) are widely used for sheathings of electrical and communication cables. However, for low fire hazard and fire-resistant cables more stringent requirements are imposed and these standards can be difficult to meet and frequently render the additional incorporation of flame-retard- ant synergists necessary, the company says. Certain synergistic flame retardants (such as
organically modified nanoclays) can negatively impact compound processability and aging performance, according to Nabaltec. To overcome this problem, it says it has developed a new flame-retardant booster — Actilox PA-B2 — that it says allows HFFRs to fulfil demanding flame retardancy standards while providing enhanced compound processability. “Furthermore, Actilox PA-B2 leads to a reduced
Figure 1 and 2: Graphs showing heat release and difference in temperature between sample upper surface and underside in cone calorimeter testing in a cable compounds containing Huber’s Hydral 710 precipitated alumina trihydrate and Safire 400 nitrogen-phosphorus fire retardant Source: Huber Engineered Materials
22 COMPOUNDING WORLD | December 2020
www.compoundingworld.com
IMAGE: SHUTTERSTOCK
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