Cost-effective metal substitution with new partly aromatic polyamides
Presentation by Dr. Rüdiger Bluhm
Application Development Universal
Engineering Plastics Europe
BASF SE, Ludwigshafen, Germany
When it comes to replacing metals with intelligent plastic solutions, one can easily lose track of the spectrum of possible applications, also beyond the realm of automotive construction. Handles for doors and windows often have internal parts made of die-cast zinc that can be replaced with plastic. Heavy and expensive metals are still being used for sports equipment, household appliances, furniture and even for thermal separators and assembly systems in solar modules. However, there are hardly any choices between standard polyamide – which does not always meet the requirements – and costly high-performance materials. In a quest to fill this gap, BASF has now expanded its Ultramid® portfolio and is introducing two new materials upon the occasion of the K 2013 plastics trade fair. Ultramid D3EG10 FC Aqua® and Ultramid D3EG12 HMG are two materials that are suitable for replacing metal in many different, and yet highly specialized, areas of application.
Balancing act between cost and performance
Aside from the two classic advantages of plastics, namely their potential for lightweight construction and function integration, an important role is also played by the thermal and electric insulation capacity of these materials. Whenever standard plastics reach their technical limits, users first turn to high-performance plastics. The actual implementation, however, is then often thwarted by cost considerations since high-performance plastics are often very expensive, particularly when they contain fillers such as carbon fibers. This is where the two new materials can come to the rescue.
Thanks to its good chemical and hydrolysis resistance, Ultramid D3EG10 FC Aqua is a polyamide specialty well-suited for components that come into contact with drinking water. This material has all of the usual drinking water approvals. And then, there is Ultramid D3EG12 HMG, which is a polyamide that stands out for its high modulus of elasticity of over 20,000 MPa. This is why it is the product of choice to replace visible die-cast metal parts since, in spite of its extraordinarily high glass fiber content of 60 percent, this material has extremely good surface properties.
These two partly aromatic polyamides were systematically developed as a high-performance complement to the standard assortment. Both of them are very stiff, display good creep behavior and are relatively irrespective of moisture in comparison to standard polyamide. For this reason, these two products lend themselves to cost-effectively replacing metal parts in almost all areas of application.
For drinking water – water meters and more
With Ultramid D3EG10 FC Aqua, BASF is also expanding its line of products developed for contact with drinking water. The special requirements stipulated for parts that come into contact with drinking water include very low migration values, a high level of taste neutrality, and substantiation that long-term contact with the plastic will not cause accelerated algae growth. Moreover, these plastics of the Aqua product line are also approved for food contact (FC).
An attractive application example of the Aqua grades is housings for water meters. Conventional brass housings have a high content of expensive copper as well as up to three percent lead to enhance processing. Lead-free materials are now acquiring greater significance since the limit value for lead in drinking water will be lowered from 0.025 mg/l to 0.01 mg/l in the member states of the European Union as of December 2013. Not least because of its strength and toughness, Ultramid D3EG10 FC Aqua is well-suited for such applications. Moreover, this polyamide exhibits reduced water absorption as well as high stiffness, and it can withstand dynamic load cases of the type encountered, for instance, when single-lever mixer taps are shut off abruptly.
More flexible than die-cast metal
The materials earmarked as metal substitutes are first evaluated in terms of their mechanical properties. They are competing with die-cast zinc and die-cast aluminum. The extraordinary mechanical properties of Ultramid D3EG12 HMG have led to the suffix HMG, which stands for “high modulus grade” and emphasizes its very high modulus of elasticity. A remarkable characteristic of polyamide is that, on the one hand, it consistently retains its high modulus of elasticity in the conditioned as well as in the dry state. On the other hand, thanks to the reduced moisture absorption, the tensile strength in the conditioned state only drops slightly as compared to the dry state. Aside from the mechanical properties, there are other characteristics such as thermal behavior or chemical resistance that also need to be taken into account. Thus, this material stands out, among other things, for a broad processing window, which is reflected in moderate mold and melt temperatures.
Visible parts made of highly filled polyamide
The new Ultramid D3EG12 HMG is thus a logical addition to the Ultramid portfolio. In spite of its high glass fiber reinforcement, this material is just right for the production of finished products having high-quality surfaces such as office chairs. This property combination alone opens up interesting application possibilities, both in visible applications and for sealing purposes. Ball shut-off valves are already being made of the HMG material nowadays.
It is precisely here that the high surface quality entails an additional advantage: the sealing surfaces of components made of Ultramid D3EG12 HMG are so smooth that there is no need for any rework. This is another strong point of the plastic version, which is why it is often the more cost-effective alternative in comparison to metal. During material development, BASF assesses the surfaces on the basis of realistic sample parts.
Economical thanks to plastics-oriented design and to parts testing
As a rule, metal designs cannot be transferred directly to plastic. As a matter of principle, a plastic part should be designed completely separately from the precursor variant. Precisely when the switch is being made from a metal to a plastic solution, it is often practical and economically advantageous to work with appropriate simulation programs as soon as possible, that is to say, already during the initial concept for the component, and also to utilize available plastic know-how. BASF experts are on hand to help customers with expertise in materials and processes in order to maximize the technical and economic potential of a plastic for a specific application. Conversely, however, it can also happen that a metal solution is the more economical variant, particularly in the case of simple geometries.
In individual cases, BASF offers the possibility to test components. For instance, the BASF flow laboratory has facilities to test the long-term resistance of water meters, pipe fittings or other parts that come into contact with water when exposed to chlorinated water at different temperatures, pressures, pH values and flow rates, even over the course of thousands of hours. Bursting-pressure tests or other customer-specific tests are likewise possible.
All in all, the new materials, along with knowledge about product behavior in realistic scenarios and with cutting-edge computational tools, open up new and promising perspectives in component development.
Information on Ultramid from BASF: email@example.com
or under telephone number +49 (0) 621 60-78780.
Press photo: At www.basf.com/pressphoto-database, under "plastics" or enter the search term "Ultramid". Text and photo will also be available shortly in the Plastics press archive of BASF at: www.basf.de/plastics/pressreleases.