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flame retardants | Additives


Right: Cables are a key


market for


LKAB Minerals’ Ultracarb


halogen-free FR additive


treatment technology, claims Don Mills, Global Sales Director in Huber’s Flame Retardant Additives business unit. From the company’s range of alumina trihydrate (ATH) and magnesium hydroxide (MDH) flame retardant products, he highlights two particular grades of magnesium hydroxide, Vertex 100 SP and Zerogen 100 SP. He says Vertex 100 SP, with a median particle size of 1.5 microns and a surface area of 14 m2


/g, allows


compounders to achieve a UL-94 V0 rating with very low smoke generation in halogen-free cable jackets. Zerogen 100 SP has an ultrafine particle size, low surface area and high purity, and is designed to provide superior high temperature, wet electrical properties in halogen-free wire and cable compounds. Median particle size and surface area are 0.8 microns and 5 m2


/g respectively. With Actilox CAHC, Nabaltec offers an LDH (layered


double hydrate) based on calcium and aluminum (CAHC stands for Calcium-Aluminum-Hydrate-Carbonate). It works as an acid scavenger in polyolefins or PVC, particularly as a co-stabiliser in Ca/Zn systems, as well as an extender for tin stabilisers. The company claims it also performs well as a co-flame retardant in PVC compounds. Nabaltec says that if PVC compounds require strict


flame retardant properties and low smoke emissions, then typically antimony trioxide (ATO) or a huge amount of ATH (aluminum hydroxide) are added as flame retardant additives. “While flame retardant low smoke compounds with high ATH loadings have to struggle with mechanical restrictions, ATO is under pressure due to its suspected carcinogenic potential for humans,” Director Michael Klimes says. “The flame retardant effect of Actilox CAHC is comparable to that of metal hydrates like ATH or MDH (magnesium dihydrate). In case of fire the material decomposes under absorption of energy.” This decomposition leads to a cooling effect while the


released carbon dioxide and water vapour dilute the burnable gases. The remaining calcium-aluminum- oxide forms a stable char, which prevents the polymer from further decomposition and also acts as an effective


Right: LKAB Minerals produces Ultracarb


halgoen-free FR from


hydromagnesite and huntite deposits


smoke suppressant. “If an ATH like our Apyral 40CD is combined with Actilox CAHC, a synergistic flame retardant effect can be obtained,” says Klimes. “This results in lower heat emission and less smoke produc- tion compared to pure ATH filled compounds. Further- more, the total amount of filler can be reduced, which has a positive effect on the mechanical properties.” Klimes also notes that some compounders may use


zinc borate as an effective smoke suppressant in PVC, but have to fight “zinc burning” behaviour. “To avoid or balance this decomposition of PVC, Actilox CAHC as acid scavenger can help and enhance the thermostabil- ity,” he says, adding that with a combination of different inorganic flame retardants, it is possible to reduce or even replace ATO in the formulation.


Attractive economics At LKAB Minerals, Business Area Manager Peter Duifhuis says the company “clearly sees a trend towards an economically attractive alternative to chemi- cally produced halogen-free fire retardants. He says that in UltraCarb, a halogen-free fire retardant produced from LKAB Minerals’ own natural hydromag- nesite and huntite deposits, the company is well-placed to address that trend. The hydromagnesite supports the water release


starting at around 220°C whereas the huntite is responsible for CO2


release at around 450°C. At around


600°C the char stabilization begins. UltraCarb is especially good at reducing smoke in thermoplastics such as PVC, the company says. LKAB Minerals is currently working on a lifecycle


analysis of UltraCarb and results will be published in 2016. “We are currently implementing our next generation grades of UltraCarb for the use in halogen- free thermoplastics to provide 100% halogen-free solutions to the industry,” says Rob Lammertink, the company’s R&D Manager. Paxymer says it has designed a novel flame


retardant mechanism that works by propagating cross-linking in the backbone of the polymer in a fire


20 COMPOUNDING WORLD | December 2015 www.compoundingworld.com


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