Presentation by Dr. Matthias Scheibitz
Product Development Automotive
Engineering Plastics Europe
Since BASF introduced the first glass fiber-reinforced PA610 injection molding grades of Ultramid® S Balance at the K 2010 Plastics Trade Show, the material has found use in numerous applications because of its special characteristics. Because of the current demand in the market and on the basis of its years of experience in extrusion, BASF decided to expand its PA610 line of products. At the 2013 it will introduce two flexible grades of Ultramid S Balance that are suitable for extrusion of pipe and tubing intended for use specifically in the automotive and machinery sectors as well as for oil and gas lines. They have the designations Ultramid S4Z5 Balance and Ultramid S4Z4 XS Balance. In this way, the company is reinforcing its position as a supplier of specialties for the extrusion field as well. The two new products will be available in sample quantities as of November 2013.
Twice flexible, resistant to chemicals and low-temperature impact
Ultramid S4Z5 Balance is a semi-flexible grade for liquid-conveying lines that must satisfy demanding temperature requirements. Ultramid S4Z4 XS Balance, on the other hand, is a particularly flexible product for vacuum and vent lines. It is characterized by even greater resistance against stress cracking.
The formulations for the two new compounds use a high-viscous polyamide 6.10 that is modified further to achieve good low-temperature impact strength. The very soft Ultramid S4Z4 XS Balance gives tubing great flexibility and in this way simplifies installation. The two products differ in terms of their stiffness and toughness. The burst pressure and fitting retention force are somewhat higher for the S4Z5 grade. It also exhibits somewhat better performance in terms of heat aging, while the S4Z4 XS grade is characterized by a further optimized zinc chloride resistance.
Specialty polyamides for injection molding and extrusion
Since their market launch, the Ultramid S Balance injection molding grades have proven their usefulness in numerous applications. Because of their particular resistance characteristics to fuels and salts that initiate stress cracking, they are used for quick connectors on fuel lines, for instance. This stress cracking resistance is also the basis for the material’s application in sensors, additionally supported by its reduced water absorption. Thanks to its interesting appearance and feel, the PA610 material, being partly based on renewable resources, is well-suited for design objects such as the Wästberg Winkel w127 desk lamp.
Because of its chemical composition, PA610 is considered one of the so-called long-chain polyamides. This family also includes PA612, PA12, PA11 and more recently PA1010, PA1012 and PA1212. They are all characterized by especially low moisture uptake compared to PA6, 66 or 46 as well as good resistance to chemicals and stress cracking. The market for this polymer family can be divided into injection molding and extrusion applications. The ratio is approximately one to four. Extrusion is dominated by PA12 because of its special property profile. However, there are also applications that require the use of other polymers because of more demanding thermal stability and fuel permeation requirements. Here, the properties of the PA610 and PA12 materials complement each other very well.
PA610 versus PA12: Heat resistance versus stress cracking resistance
The individual mechanical properties of PA610 can be customized through appropriate formulation. As a result, these products are in no way inferior to PA12 in terms of flexibility, stiffness and toughness. Elongation of up to 200% can be achieved, a typical requirement in specifications for tubing systems in automobiles. Thanks to the high melting point of 222°C Ultramid S Balance also satisfies continuous-use and peak temperature demands at which PA12, with its melting point of 178°C, reaches its limits. In view of ever more powerful compact engines in ever smaller engine compartments, this property is important, since engine compartment temperatures of up to 150°C are not uncommon and components must be able to withstand them. The decisive aspect when it comes to material selection is the difference between the mechanical properties in the dry and conditioned states of Ultramid S Balance, a situation that is not as pronounced or does not even exist in the case of PA12. BASF's experts have formulated the newly developed products to have properties comparable to those of the PA12 grades in the conditioned state.
The stress cracking resistance of the PA610 material falls between that of PA66 and PA12, which because of its chemical structure is nearly insensitive to stress cracking. Nevertheless, Ultramid S Balance can be used in parts that come into contact with solutions containing CaCl2, which is used as road salt in cold climates, and ZnCl2, which can be encountered on zinc coated parts. Stress peaks can be avoided in tubing systems, for instance, through use of elegant welding solutions as an alternative to the classical retaining ribs of the fitting.
With a glass fiber reinforcement of 30%, Ultramid S3WG6 Balance has already established itself as a material for quick connectors in fuel line systems because of its good swelling characteristics in different fuels. Because of its more polar structure, PA610 sometimes offers better fuel permeation characteristics than PA12, which for many years has had a well-established position as a standard material for fuel lines. Suitably structured multi-layer systems, a field in which BASF has built up extrusion expertise over many years, can compensate for any drawbacks. When extruding pipes, PA610 processes just as easily as PA12; because of its higher melting point however, higher processing temperatures are to be expected.
From coolant to compressed-air brake lines
As a rule, the user must consider each case individually in order to obtain a technically as well as economically optimal solution. The requirement profiles of different lines in the automotive sector differ from one another considerably: Coolant lines must have low-temperature impact strength and significant resistance to heat aging. High chemical resistance and similarly high hydrolysis resistance are required. Because coolant systems operate under pressure, a high burst strength is needed. Finally, the material must also withstand high ambient temperatures.
Vacuum lines must exhibit flexibility and low-temperature impact strength. Resistance to chemicals, high ambient temperatures of up to 140°C and stress cracking is an additional requirement. The same resistance to sometimes very aggressive chemicals and hydraulic fluids as well as engine oil is expected of a clutch line. Such lines have high internal pressures, and for this reason their volume must remain as constant as possible, as otherwise the force needed to operate the clutch pedal will vary. Crankshaft or crankshaft housing vent lines discharge a mixture of oil vapors and combustion gases. They are in close proximity to the engine and subjected to considerable stress. Air brake lines, on the other hand, are not protected from external factors at all, since they are usually attached directly under the chassis of trucks. High impact strength, even at low temperatures, are basic requirements for materials used in these applications. High stress cracking resistance when exposed to calcium and zinc chloride is just as necessary as high burst strength.
These complex requirement profiles show that there is a significant demand for customized solutions here. With these first two Ultramid S Balance grades, BASF has begun its development activities in the field of custom-formulated extrusion products for tubing and liquid-conveying lines. Additional products developed in conjunction with customers will be available in the future.
Special grades for the US market
The new Ultramid S Balance extrusion portfolio is supplemented exclusively in the USA by the Ultramid HFX product family that has been already available there for some time: Here, too, the application fields of these polyamide extrusion grades are flexible tubing and pipe applications for hydraulic, air brake, vacuum, and HVAC hoses and for paint sprayers. Current applications of the latest grade Ultramid HFX 51 include oil and gas tubing where the requirement is for an easily processable polymer that can deliver high flexibility, strength and toughness combined with heat and chemical resistance.
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