FLAME RETARDANTS | INNOVATION
such as polyamides. The company says the product is especially suitable for use with HFFR compounds “since incorporating the additive improves not only the flame retardant properties but also the drop- ping behaviour and crust formation.” Byk-Max CT 4260 also enables the filler content — aluminium, or magnesium hydroxide, for exam- ple — to be reduced. This leads to a measurable improvement in processing and physical properties and to a reduction in the overall weight, Byk says. It can also enhance barrier to oxygen, water vapour, and hydrocarbons while increasing melt viscosity, enabling in some cases an improvement in dimensional stability during profile extrusion. At Budenheim, Heiko Rochholz, Head of
Marketing, says with its new Budit 617, the com- pany “offers a new class of HFFR system that addresses the need for a higher GWIT (>800 °C) and less corrosion while processing.” Budit 617, which is based on melamine polyphosphate in a new synergistic combination, is intended for use in glass fibre reinforced polyam- ide 66, where it can provide up to UL94 V-0 at 0.8 mm. It does not discolour the polymer and does not migrate to the part surface. Decomposition starts above 340°C. “Due to its high phosphate and nitrogen content it acts as a flame retardant mainly in the solid phase [char formation] but has addi- tionally a synergist (DOPO derivative) acting in the gas phase,” says Rochholz. Budenheim is also now offering Budit 669S, a development of its existing Budit 669 grade that is suitable for use in polyolefins, especially cables, tubes, and housings of white goods. 669S is an ammonium polyphosphate (APP)-based halogen- free flame retardant containing a special coating. Compounds using it are said to offer better
mechanical properties. In addition, there is no migration and V-0 can be achieved at 1.6mm.
Circular innovations Addressing issues of the circular economy, Clariant says there is a growing need for flame retardants for polymeric compounds that are not only efficient and stable but also environmentally friendly. It says that for its Exolit halogen-free flame retardants for polyamides and polyesters, it has developed a rigorous method to screen products based on a catalogue of 36 criteria to determine their environ- mental impact. Based on this extensive evaluation process, products that meet the criteria can be awarded its Ecotain label. The company cites Exolit OP 1400 for polyamides as an example. It says it “combines sustainability with the ability to meet the stringent requirements of e-mobility like UL94 V-0 down to 0.4 mm and the best CTI of 600V.” For thermoplastic polyesters, Exolit OP 1260 has also been awarded the Ecotain label, in part due to good recycling performance demonstrated in a recent study of PBT 30% glass reinforced compounds with and without flame retardants. Specimens were moulded from fresh compound with the addition of 10%, 30% and 50% regrind. The Exolit-based compounds retained the flame retardancy standard UL 94 V-0 at all levels of re-grind addition. Even the afterburning times were not significantly affected, the company claims. The mechanical properties including elongation remained unchanged as well. “Under the conditions used in the test, Exolit OP 1260 can be used as a drop-in replacement to brominated flame retardants,” says Clariant. Progress is also being made in flame retardants based on graphite, with George H Luh’s new expandable graphite grade developed especially for polyamides. The company, which provides materials from various sources, says that, until now, the expansion initiation temperature of maximum 230 °C has limited the use of expandable graphite in polymers with relatively high melting points such as polyamide. “With our new generation expand- able graphite GHL PX 95 HT 270, we have been able to develop a new grade that only develops its protective characteristic from 270°C,” says Market- ing Manager Angelina Schöffel. “It can be used for polyamides and applications with processing temperatures up to 260°C.” Quantities for sampling and first production
Figure 4: Clariant’s Exolit OP 1260 flame retardant offers a good balance of properties in glass reinforced PBT compounds Source: Clariant
26 COMPOUNDING WORLD | December 2020
trials are available now. The company says the next step is the development of expandable graphite grades with even higher starting temperature and various particle sizes.
www.compoundingworld.com
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