ADDITIVES | FLAME RETARDANTS
project involved determining how much extra FR material (ATH) was required when replacing an EVA with a 28% VA content (Escorene UL00328) with a POE (Exact 5371), as well as optimisation of the POE-based formulations.
While a compound based on EVA with 28% VA content would typically require 60% (160phr) ATH (Martinal OL-104 LEO) it was possible to achieve comparable flame retardant performance from a compound based on POE with 68% Martinal OL-104 LEO (220phr) or 66% (200phr) of a finer grade, Martinal OL-111 LE. Higher values of elongation were achieved with the POE formula- tions, despite higher loadings of the flame retard- ant, says Huber. Further benefits from the POE compounds included lower water uptake and much lower smoke production. Lower values of tensile strength, hot knife behaviour and melt flow were countered by adding LLDPE to the formulation. And as the density of POE is less than EVA, the required higher loadings of flame retardant could be achieved while keeping compound density at an “appropri- ate” level, according to Huber. One of the most interesting potential customer benefits of using the POE/Martinal OL-104 LEO combination is in the opportunity to reduce material costs for HFFR compounds. Gains in the the range of around 10% are possible driven by the higher FR loading than in the reference compound, Huber says.
Norwegian start-up Bioenvision has developed
flame retardants for various thermoplastics based on POSS (polyhedral oligomeric silsesquioxane) technology. The company describes POSS addi- tives as organic/inorganic hybrid polymers that have the potential to improve product perfor-
mance without sacrificing mechanical properties. Bioenvision markets its POSS-based flame
retardants as D-Pyre. It is the holding company of Funzionano, originally part of Norway’s SINTEF research institution, which developed a nanotech- nology platform for flame retardants, water repellents, and barrier materials over a period of more than 15 years. Results presented at AMI Fire Resistance in Plastics conferences have shown D-Pyre can improve performance of diverse polymers such as PVC, PP and PUR foam, reducing dripping and cutting the time to flame extinguishing of PP in the UL94 test, for example. Required dosages are low — typically between 0.6 and 1.7% — and when used in combination with other flame retardants such as ATO or ATH they can reduce the required amount of the FR by as much as 30%.
Investigating halogens Fire retardant research, innovation and product development is not limited to halogen-free chemis- try. Fire retardant producer Albemarle continues its strong Advocacy and Product Stewardship pro- gramme in brominated flame retardants, investing in new analytical instrumentation, including a high-resolution LC mass spectrometer, to address questions from regulatory agencies. For example, it recently published a study on photolytic perfor- mance of ethane-bis(pentabromophenyl) (EBP), which it produces and markets as Saytex 8010. The company says this accelerated weatherom- etry study conclusively showed that in HIPS, a commonly used resin for electronic enclosures, the EBP molecule has a much slower loss of a single bromine atom. The estimated half-life is more than 200 years (Figure 5), whereas the half-life of the decabromodiphenyl ether (decaBDE) molecule can be measured in days. “More importantly, no further loss of bromine
Figure 5: UV photolysis of EBP in HIPS using a Xenon lamp (to mimic aging due to solar exposure under ca. 13-fold accelerated conditions) showed no formation of lower brominated species of concern and very slow loss of bromine (estimated half-life more than 200 years) Source: Albemarle
30 COMPOUNDING WORLD | December 2022
atoms to smaller molecules of concern occurred. In polypropylene (PP), there was no observed loss of bromine, even though the FR loading is nearly twice that in HIPS. The key takeaway of this study was that a read-across comparison from DecaBDE is misleading and that EBP is a safe polymer additive,” it says. “Albemarle continues to advocate for a data- based approach in determining the health and environmental impact of any material. We know structural differences matter, and that they affect chemistry and performance. Over-generalisation by putting all molecules into one class is inappro- priate,” says Bob Miller, VP of Product Stewardship. “We will continue to use scientific studies such
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