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additives feature | Flame retardants

A nitrogen/phosphorous FR compound was specifi ed for this UL94 V-0 generator cover moulded by Bosch using PA 66 from BASF

business director for the fi re resistance business unit of Rhodia, a resin producer (mostly PA 66) and compound- er that is part of the Solvay Group. Mitchell highlights the diffi culty of working with a wall thickness of 0.4 mm by saying that such a material is virtually fi lm. There is also the ongoing issue of reducing cycle times, which raises performance questions. “Faster cycle times demand faster crystallization capability [in polyamide] while maintaining good dimensional tolerance,” remarks Invista’s Gopal. FR additives must be tailored for these changes as well. Many of these challenges impact other applications.

retardant, ridding the matrix of water and air voids and creating a continuous phase”. This is said to dramatically lower compound viscosity, thereby “reducing resin demand for a given pigment-to-binder ratio.” The chief benefi t, Monte notes, is that more fl ame retardant can be added without sacrifi cing processability. Monte states, for example, that “when 50% melamine

cyanurate is dispersed in mineral oil, the in-situ addition of 0.7% Ken-React KR 238NF” reduced Brookfi eld viscosity to 30,000 cps at 25°C from 1.6 million cps.

Impact of product trends Market trends infl uence additive formulations. Among the most signifi cant are the downsizing and miniaturi- zation of electrical and electronic devices. As parts become smaller, thinner and more densely packed in assemblies, FR additives must meet challenging fi re and smoke requirements, as well as resist arcing and short-term bursts of electromagnetic energy, maintain dielectric strength, and withstand high continuous-use temperatures and heat aging. Where higher-heat lead-free soldering is used for regulatory reasons in circuit boards and other applications, FR additives must maintain properties without decomposing. “Like everything else in the electronics industry,

form factor is becoming smaller,” says LeeAnn Dombrowski, electrical and electronics market segment manager at BASF. “As a result, FR additives have to be even more effective than before, as fl ame resistance has to perform the same but with thinner cross sections. Materials for connectors in the appliance segment are now looking at glow wire certifi cations at 0.4 mm thickness versus 0.75 mm previously.” This is the new normal for many electrical and electronic parts, affi rms James Mitchell, global

26 COMPOUNDING WORLD | December 2012

In automotive, greater under-the-hood use of engineer- ing PAs and higher underhood temperatures generated by small, fuel-effi cient engines raise performance requirements of FRs. Similarly, the use of PA in high-voltage components of electric and hybrid vehicles, such as batteries, power electronics and other types of electric vehicle specialty equipment (EVSE), raises heat, mechanical and other performance requirements for additives. BASF’s Dombrowski says that while automotive

components have typically been rated at UL94 HB, “we will continue to see more applications requiring UL94 V-2 or V-0 fl ammability ratings due to the introduction of high-voltage components.” Additional concerns include the interaction of FR additives with UV stabiliz- ers, since EVSE components such as vehicle chargers have signifi cant outdoor exposure.

The green infl uence Environmental considerations play an ongoing role in FR chemistry, as OEMs continue to move away from halogens in formulations. Specifying a fl ame retardant chemistry for PA is sometimes helped by the inherent properties of the polymer. PA 66 has inherent UL94 V-2 performance, and is generally credited with outstanding tensile strength at elevated temperature and good processability, both of which aid in fi nding compatible FRs and facilitating product development. Some resin producers are tweaking PA 6 formulations to improve mechanical properties such as modulus, bringing the stiffness of grades near that of PA 66, which also broadens additive selection. Importantly, regulation of FR additives is becoming a

global standard. OEMs and other manufacturers don’t need to worry about complying with different regulatory rules when specifying FRs. “Flame retardants is the only fully global business in engineering polymers,” says Rhodia’s Mitchell. “The regulatory standards in China are as high as in Europe and elsewhere. A lot of what’s produced in one country is shipped around the world. There is no need to reinvent the wheel when it

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