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Flame retardants | additives feature


Pat Toensmeier speaks with resin producers and additives suppliers to fi nd out the latest trends and technical developments in fl ame retardants for polyamide compounds


Picking fl ame retardants for polyamides


Polyamides are widely used in high-volume markets such as the automotive, electrical, electronics, appliance and industrial sectors. Like all engineering thermoplas- tics, polyamide (PA) formulations are continually tweaked to enhance properties and performance for changing applications and regulatory needs. One critical formulation area for PA is fl ame-retard- ant (FR) additives. Resin producers and compounders are working with FR suppliers on a range of additive chemistries to meet shifting fi re and toxicity require- ments while minimizing trade-offs in performance and cost. Almost all new FR grades are free of halogens and bromines, which are effective and economical, but for regulatory and environmental reasons are being phased out of many applications. In their place, additive suppliers and resin producers


are seeking alternative FRs that do not affect the properties of PA formulations, including those that use reinforced grades. Other considerations include FRs that do not migrate during processing or use, have no affect on part colour, and importantly, do not impede processing or contribute to machine corrosion from release of by-products. Melamine compounds, alkylphosphinates, phosphorus


derivatives and metal hydroxide are among the leading materials that are being specifi ed in PA grades for fl ame retardance, says Steve Hanley, product development manager for engineering plastics at PA 6 producer BASF, which also makes FRs. These chemistries are compliant with international regulatory standards, yield low levels of


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smoke and corrosion, have minimal effects on electrical properties, maintain high-temperature stability and are compatible with colours. Many companies are also looking at innovative


co-fl ame retardant combinations, which along with the use of synergists such as boehmites (an aluminium oxide hydroxide), achieve properties at lower loadings. The chief benefi t is that “fl ow is not as greatly affected” during moulding, extrusion or compounding, explains Hanley. Maintaining thermal stability in higher processing


temperatures and end-use environments also affects FR chemistries. “There is a lot of work underway in non-halogenated chemistries, mostly for fl ame retardants based on phosphorous or nitrogen-contain- ing materials,” says Richard Wenger, technical product manager for the PA 6 business of DSM, which also produces PA 46. “At elevated temperatures low-level


Target


applications for fl ame retardant polyamide


grades include critical


automotive


components such as this Peugeot 508


relay and fuse box


Densely packed circuit boards that use high-heat lead-free soldering demand upgraded FRs


December 2012 | COMPOUNDING WORLD 21


PHOTO: A2MAC1 AUTOMOTIVE BENCHMARKING


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