MATERIALS | FLAME RETARDANTS
by Italmatch Chemicals using thermally stable inorganic phosphorus salts (hypophosphites) has been commercial for several years. Grades can be used alone or in combination with other FRs. The supplier says the versatility of its technology is due to the multiple mechanisms employed; it works in the gas phase and also has a charring effect and prevents dripping. Grades are based on calcium hypophosphite and aluminium hypophosphite. The first is a relatively water-soluble salt with high phosphorus content (37%) and exceptional thermal stability; the second a low water-soluble molecule with very high phosphorus content (42%) and high thermal stability.
Above: Electric vehicle batteries are driving
demand for flame retardant plastics
recently commercialised graft-modified PET compounds incorporating Nofia additives.
Supply challenges On the commercial side, Lebel says that producers of phosphorus-based and PN flame retardant additives have suffered from the Chinese govern- ment’s decision earlier this year to curtail power to several provinces. He says this has caused ripples through numerous supply chains, one of them being the energy-intensive production of white or yellow phosphorus (P4
Among the company’s most recent develop- ), Lebel estimates around one
third of capacity was taken out, leading to prices more than tripling at one point in late summer/early autumn. Over 90% of halogen-free flame retardants (HFFRs) are based on P4
, accordingto Lebel, who
says FRX sources supplies from outside as well as inside China so has not been shorted. Phoslite flame retardant technology developed
ments are Phoslite B85AX and Phoslite B64AM, which form the basis for thermoplastic polyurethane (TPU) formulations for cable compounds. They can be combined with Italmatch’s Melagard MC melamine-based flame retardant to create products with a V-0 rating at 1.6 mm with a total additive loading of 30% (of which 25% is Phoslite B85AX). Two new developments and entries into the thermoplastics marketplace are highlighted by Huber — the Kemgard 600 smoke suppressant series and Safire 400 nitrogen-phosphorus fire retardant technology. The Kemgard 600 series is partially based on
molybdate chemistry and comprises three grades: Kemgard 606, Kemgard 620 and Kemgard 631. Primarily intended for rigid and flexible PVC applications, they catalyse crosslinking in the polymer matrix, leading to improved organic char
Improving flame retardant dispersion
Evonik organo-modified siloxane (OMS) chemistry (branded Tegomer and Tegopren) provides intrinsic properties that can be advantageous for flame retardants, enabling homog- enous dispersion of the flame retardants in the polymer matrix without compromising the mechanical properties. The additives – which are resistant to high temperatures and do not generate degradation bi-products during fire — can be added during production of the flame retardant or as part of the compounding process to improve charring, delay the time of ignition, reduce heat release rate and smoke generation, and increase LOI (by up to 5 points). Tegomer V-Si 4042 is an example for such additives. Evoniks’s Tegopren 6875 and Tegopren 6879 additives
create hydrophobic flame retardant surfaces. The surface treatment is not only suitable for oxides but interacts with nitrogen and phosphorus based flame retardants. �
www.evonik.com
22 COMPOUNDING WORLD | December 2021
Heat release of EVA compounds containing 65% ATH and MDH with and without Evonik’s Tegomer V-Si 4042 organo-modifed siloxane additive
Source: NGR
www.compoundingworld.com
IMAGE: SHUTTERSTOCK
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