high temperature plastics | Innovation
Right: ConMed Linvatec’s Hall Lithium Battery system for surgical tools uses a casing in Solvay’s AvaSpire to allow it to be autoclaved at temperatures up to 134°C
polyamide 4,6 for the latest generation of synchronous dynamic random-access memory (SDRAM) connectors. These DDR4 connectors put very high demands on the plastic housings in terms of thermal and mechanical performance. DSM says its high performance polyamides have the right combination of high stiffness and high defl ection temperature under load (DTUL). Meanwhile, DuPont says its Zytel Plus modifi ed polyamide (6 or 6,6) provides the superior temperature and chemical resistance required for demand- ing automotive engine, drive train and cooling uses. The polymer stands up to hot air, hot oil and hot water, gives parts with very good surface appearance, and has the high fl ow and ease of process- ability that polyamides are known for. Zytel Plus uses DuPont’s Shield Technology, which
the company also applies to its Zytel HTN92 PPAs. DuPont provides little detail on the functioning of its Shield Technology, saying only that it “combines several innovations, including a new polymer backbone, polymer modifi cations, and a special set of additives to enhance many performance characteristics.” Zytel Plus is claimed to last two to three times longer than other polyamides when exposed to aggressive chemicals. It withstands 4,000 hours of exposure to hot air, and more than 3,000 hours exposure to hot oil or hot automotive coolant. It also retains the majority of its weld strength after 1,000 hours at 210°C, at which point it will have dropped to almost zero in many other materials.
DuPont says that, owing to their aromatic nature,
PPA resins with Shield stabilisation have demonstrated especially superior perfor- mance at high temperatures, creating the possibility for replacement of PPS in some situations. The new Ford 3.5L and 3.7L PA6 engine manifold uses a cross-over coolant component made of DuPont’s Zytel HTN PPA resin instead of brazed metal, shaving close to half a kilo off the weight in this drop-in replacement. Developed with ITW, the crossover is a hollow port that allows engine coolant to bypass the manifold as it circulates through the engine. It was previously
manufactured in brazed metal because PA 6
does not withstand long-term exposure to heat and long-life coolant. DuPont says Zytel HTN PPA is frequently used in
engine cooling components because it can withstand the long term exposure to heat and long life coolant, but the intense pressure of the overmoulding process needed to integrate the component into the Ford manifold system was damaging the hollow component. The team modifi ed the material and the design using advanced computer modelling and ITW invested in cavity-pressure sensing technology from RJG to provide data to pinpoint where design changes could add structure.
Selective applications
“There’s a growing trend toward using high-perfor- mance materials only where they are needed,” says Pat Granowicz, powertrain segment leader, DuPont Automotive Performance Polymers. “This can lead to challenging designs and demand innovative processing solutions. Modelling based on how a material behaves in processing and in use is critical.”
Stress at break for various polymers after oven ageing at 210 °C. Measured at 23°C, per ISO 527. (S indicates DuPont Shield technology)
62 COMPOUNDING WORLD | June 2014 Source: DuPont
Radici has extended its Radilon HHR line of high- heat-resistant specialities with the introduction of the Radilon Xtreme series. It says the modifi ed polyamide 6,6 products feature excellent high-heat ageing resistance. They are available in 15%, 20% and 35% glass-fi bre-fi lled versions. Radici claims they can be used as metal or special polymer replacements. Radilon XTreme has a melting temperature of 280°C, which is 20°C higher than standard PA66, and its glass transition temperature is also similarly higher, at 90°C. Moisture absorption at saturation is 7%, which is 25% less. The materials were developed for hot-air applica- tions at continuous operating temperatures of up to 230°C. Grades are intended for use in such automotive applications such as turbo air ducts, EGR heat
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