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New flame-retardant nylons |
Progress in engineering plastics
New flame-retardant nylons
Presented by Dr. Ralf Neuhaus, Marketing Ultramid®
Trade Press Conference K 2004, June 22, 2004, Ludwigshafen, Germany
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Nylons - polyamides to give them their chemical name - are organic substances and therefore potentially flammable. Many applications of course require that the materials used inhibit flame spread or cause the flame to be extinguished. Since nylons have only very limited intrinsic flame-retardance properties, it is often necessary to add special flame-retardant substances to the moulding compound.
The assessment of the flammability of materials, which has a direct bearing on their suitability for a particular application, is governed by numerous technical standards and safety regulations. Apart from safety, a material must also fulfil many - sometimes conflicting - requirements, which include good mechanical, electrical and thermal properties, good processability, low toxicity, and not least, price (figure 1).
BASF attempts to satisfy the different market requirements by offering a wide range of flame-retardant grades based on nylon 6, nylon 66 as well as nylon 66/6 copolymers. The product variety is derived from the combination of various halogen-free flame-retardants, glass-fibre reinforcement and other additives (figure 2).
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Flameproof, tough and stiff
Grades within the Ultramid range can be roughly distinguished by the presence or absence of a reinforcing filler. The unreinforced C3U for example is required for applications that demand good flame-retardance (UL94 V0) and also good toughness for features like snap connectors. An example of such an application is electrical terminal blocks.
On the side of the reinforced products, there is the A3X2 series of grades with red phosphorus flame-retardant and glass contents between 25% (G5) and 50% (G10). Typical uses for such resins include industrial electrics and household appliances, when poor flammability (UL 94 V0) and a good balance between toughness and stiffness are what matter. B3UG4 and the more heat resistant C3UG4 do not rely on red phosphorus and are therefore naturally pale in colour. This is advantageous because the resin is freely colorable in almost any shade; however, the price to be paid for this is a somewhat worse flammability rating (UL 94 V2).
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Three new developments
To meet the ever-growing demand of markets, BASF has to work continuously to develop new products. One such development is Ultramid B3U HF, an unreinforced nylon 6 with a halogen-free flame-retardant. Because this material is suitable for the thin-walled housings of electrical equipment, which require a UL94 rating of V0, particular emphasis is placed on good melt rheology. The easy-flow property becomes very noticeable from the short moulding-cycle time. Other typical nylon properties such as impact strength, good surface finish and environmental stress-cracking resistance round off the property profile (figure 3)
Another new development concerns a halogen-free FR nylon 6 for circuit breakers, Ultramid B3UM4. By using a suitable low-cost mineral filler, it is possible to offer customers considerable cost savings, while keeping losses in mechanical performance to a minimum. Other advantages of this product are low density and low warpage (figure 4).
The third new product is Ultramid A3UG5, a flame-retardant reinforced nylon 66 that contains no halogen or red phosphorous. A new pale flame-retardant additive makes it possible to formulate V0 rated, glass-reinforced nylons that are freely colorable. Thanks to their low density, such compounds are an ideal alternative to halogenated flame-retardant products (figure 5).
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