Rhodia Engineering Plastics has pulled off something of a polymer technology coup by developing an unalloyed nylon 66—for automotive online-paintable external body panels and components—that it says is capable of withstanding e-coat temperatures of 200C (392F) for 30 minutes. The grade is intended for such parts as vertical panels, fuel filler flaps, rocker pillars, front grilles, and exterior trim applications.
Technyl A 238P5 M25 is said to meet all critical application requirements in impact, surface appearance, and processability. Parts have a uniform electrical conductivity (more Rhodia technology), enabling them to be painted electrostatically without a conductive primer.
The most widely used thermoplastic for fenders, GE Advanced Materials'' Noryl GTX, is an alloy of nylon with polyphenylene ether (PPE). GEAM says the PPE provides the necessary high-temperature resistance, but only Renault uses it for online painting, with other companies preferring to attach the panels to the car after the e-coat.
Last year, Bayer Polymers (as it was then called) introduced a rival material, also a nylon alloy, but in this case paired with ABS. Rhodia says it can get better properties from a pure nylon 66 and "specific fillers." It says sag test results, up to 220C (428F), demonstrate the "substantial advantage" of Technyl A 238P5 M25 over competitive materials. Parts also expand less at high temperatures, and Rhodia claims higher molding productivity through lower cycle times and part-reject rates.
Rhodia also has two new grades of 30% glass-fiber-reinforced nylon 66 (Technyl A 338Wit1 V30 bk34N and Technyl A 338Wit2 V30 bk34N) for engine cooling pipes made using water-assisted injection molding (WIT). The key difference between these and existing grades used in WIT, which were originally developed for gas-assisted molding (GIT), is the superior quality of the inner surface. This is due to a more even glass-fiber coverage by the polymer, along with a constant wall thickness free of water inclusion. This translates into greatly reduced pressure loss in the cooling circuit, and a reduced risk of fibers coming out of the matrix and polluting the cooling fluid.
Rhodia says the new grades also show an optimal balance between processability and glycol resistance. The tensile strength at break of Wit1 after 1000 hours at 130C (266F) in a mix of water and glycol is as good as that of GIT grade A 218Z V30 bk34N, and it is 15% higher in Wit2. Improvements in impact resistance are 80% and 100% respectively.
One six enough for DSM
Meanwhile, DSM says its Akulon nylon 6 offers performance equal to or better than many competitive nylon 66 formulations, with a significantly better price-to-performance ratio. Product manager Bert Havenith says Akulon shows better retention of strength—both at ambient temperature and above 100C (212F)— after heat aging, higher impact resistance at low temperatures, and much better processability, yielding better surface appearance, higher weld strength, and lower processing costs.
DSM is now into its second generation of Akulon Ultraflow, which is tougher than first-generation types. Akulon Ultraflow has 80% better flow than regular Akulon, as measured in spiral flow tests (photo). This can lead to cycle-time reductions of up to 40%. It also means that molded parts have good surface finish, even when compounds containing as much as 60% glass fiber are used. The material is close to commercial approval for use in such parts as electrical hand-tool housings and car mirror shells. In both cases, molders are experiencing cycle time reductions of about 35 to 55 seconds. An engine cover due to appear on a car launching in 2005 will have a wall thickness of 2.5 mm, instead of 3.2 mm.
Akulon Ultraflow is available in formulations with reinforcement up to 50% glass, as well as glass/mineral combinations. Typical applications include underhood automotive components and assemblies, door handles and mirror brackets; electrical components; power tool and lawn-and-garden enclosures and housings; and ski bindings. DSM Engineering Plastics, Sittard, The Netherlands; +31 46 47 73522; www.dsmep.com. Rhodia Engineering Plastics, Lyon, France; +33 4 72 89 27 53; www.rhodia-ep.com
Flexible vinyl used for enhanced heat stabilizers
By using more efficient, proprietary heat stabilizers than conventional medical-grade PVC, the new Apex line increases manufacturing throughput. It allows extrusion processors to run machines at higher rates with fewer screen changes, and injection molders to fill thin-walled parts without worry of high shear. After production, the stabilizer allows components to be shipped and stored without concern for heat levels, and enables autoclave sterilization without discoloration or degradation.
FDA regulatory restrictions don''t allow barium-zinc and other heavy-metal-containing heat stabilizers in medical parts. Teknor Apex''s medical compounds are heavy metal-free, but they reportedly have thermal stability similar to compounds containing heavy metal stabilizers.
The compounds are offered in the same durometer range as the company''s standard PVC compounds range. The first grades are clear, but opaque variations are to follow. Apex 3700 compounds are for clear extrusion of tubing used in blood transport, external feeding, oxygen delivery, dialysis, catheters, and drainage systems. For injection molding, 3800 compounds can be used to create oxygen masks, mouthpieces, adapters, valves, connectors, drip chambers, and syringe bulbs. Teknor Apex, Pawtucket, RI, USA; +1 401- 725-8000; www.teknorapex.com
Thermoplastics vie for electrical applications
DuPont has extended its Zytel glass-fiber-reinforced nylon range to include two grades with higher fire-retardancy ratings in a move to grab some of the electrical components market now using polyester bulk molding compound (BMC). According to marketing manager Brian Fish, the new grades beat BMC on cycle times and design functionality (as they allow more molded-in and assembly features), while allowing for thinner walls. The FR82G30V0 grade achieves UL 94 V-0 fire retardancy at 1.5-mm wall thickness; the other grade, FR82G33V1 is rated V-1.
Another supplier of engineering thermoplastics, Ticona, recently introduced eight hydrolysis-resistant Celanex PBT grades that meet the USCAR (United States Council for Automotive Research) Class II: 100C and Class III: 125C performance standards for electrical components. Unmodified PBT works well at the lowest USCAR level (Class I: 85C), but the combination of humidity and higher temperatures have until recently proved too much for PBT on parts requiring a higher USCAR classification; adhesion between PBT and reinforcement materials diminished as temperatures approached PBT''s glass-transition temperature. The new grades extend PBT''s potential use to both Class II: 100C and Class III: 125C, and one grade is being tested for its suitability in the most rigorous requirement, Class IV: 155C compliance. DuPont, Wilmington, DE, USA; + 1 302-774-1000; www.dupont.com; Ticona, Kelsterbach, Germany; +49 69 30516299; www.ticona.com
Specialty PP grade targets nonpressure pipes
Pipes made with high-molecular-weight PP block copolymer grade 330-NA00 are more durable than competitive clay or concrete pipe systems. The material offers the same MFR of .3g/10 minutes (2.16 kg at 230C) as its predecessor grade, 433-NA00, but its flexural modulus (1550 MPa) is higher and impact strength is similar. Charpy notched impact at –20C is 6.5 kJ. It also has long-term heat stability to insure good processability, says David Cartwright, market development manager-polymers Europe at BP. He says the market is demanding PP grades with higher stiffness. This grade will be officially launched at K 2004. BP plc, London, England; +44 7748 112288; www.bppetrochemicals.com
Elastomers extend PS appeal
Two thermoplastic elastomers are marketed for impact modification of clear polystyrene in molded parts. Finaclear 636 was launched specifically for molding transparent coat hangers. It can be blended with up to 40% crystal PS. The second grade, 609, is said to have more fluidity than standard thermoplastic elastomers to allow easier processing. Typical applications are in food containers, desktop accessories, and hinged applications such as lidded boxes. Atofina, Paris, France; +33 1 4900 8080; www.atofina.com
Polystyrene provides impact, heat resistance
Edistir R850E is an improved, so-called "super-impact" polystyrene (PS), with good heat-resistance properties. It is suitable, even in blends with high levels of general-purpose PS, for thermoformed cups, dairy tubs, lids, and flatware. The same grade can be injection molded in medium thickness for disposable food container applications requiring toughness. Polimeri Europe, SpA, San Donato Milanese (MI), Italy; +39 02 5201; www.polimerieuropa.com
Lower acetaldehydes in PET improve water flavor
By lowering inherent acetaldehyde levels, a new grade of PET specially engineered for bottled water reduces aftertastes that can be found in bottles using other resin with greater amounts of acetaldehyde. Laser+ W PET is produced by DAK Resins, a division of DAK Americas, which was once part of DuPont. In addition to low acetaldehyde levels, the resin reportedly allows processing flexibility for a variety of container designs and sizes. Improved performance in injection stretch blowmolding machines, better color retention, and thicker walls are also possible without losing clarity, all while maintaining bi-axial stretch.
The product has been selling commercially since Q4 2003, according to company spokesmen, and it''s currently in taste tests by several large-brand companies in the bottled water market. Higher acetaldehyde levels can be drawn out during the stretch blowmolding process as preforms are heated, but DAK says they''ve reduced inherent levels by half, eliminating aftertaste. By being able to withstand a higher processing temperature, DAK says cycle times during molding of preforms can be reduced by one or two seconds. The resin is also said to conduct heat well, allowing it to reheat in blowmolding machines quickly.
In the overall PET market, after dipping in 2003 when a sizable chunk of capacity came online in North America, PET producers have announced a pricing increase of $.12/lb. This hasn''t slowed consumption, which DAK hasestimated as increasing by 7.5% to 9%/yr. DAK Americas LLC, Charlotte, NC, USA; +1 877-432-2766; www.dakamericas.com
Nucleating technology improves PP processing
Hyperform HPN68L nucleating agent is now available as a masterbatch called HI5-5 that can be introduced during injection or extrusion to produce high-speed nucleation. Concentrate form allows processors to determine the optimal approach to boost productivity and enhance quality. Previously, nucleating technology was added during the manufacturing stage, which Jeff Jones, Milliken Chemical''s global marketing manager for the product line, says resulted in limited options for use.
"With the concentrated form, plastics processors have increased flexibility in how they use high-speed nucleation. This should open up [new] options for manufacturing opaque PP products," Jones says. Dosing is similar to adding color or additive concentrates.
HI5-5 is said to cut cycle times of opaque grades by up to 25% compared to non-nucleated PP products.
It also can reportedly enhance product quality through improved dimensional stability and physical property balance. Milliken Chemcial, Spartanburg, SC, USA; +1 864-503-2200; www.millikenchemical.com
Additive extends chains in reclaimed polymers
Processors hoping to use post-consumer reclaimed polyester and other polycondensate resins have been forced, because of a degradation in the materials'' mechanical properties, to reduce usage or focus on low-value-added applications. A new family of chain extenders can now enhance recycled condensation polymers such as polyesters, polyamides, polyurethanes, and polycarbonates.
CESA-extend, a joint introduction by Clariant Masterbatches and Johnson Polymer, is a family of additive masterbatches that can relink chains within the polymer matrix, leading to increased molecular weight, as well as improved mechanical and rheological properties and processing, allowing recycled polymer use in more demanding applications.
The additive is based on a proprietary, patented technology consisting of multifunction acrylic oligomers that are used in condensation polymers in low concentrations to enhance their properties. Clariant Masterbatches and Johnson Polymers appreciate the market for such an additive, noting that 700 million lb of recycled PET is consumed annually in the U.S. The companies say that their multifunctional oligomeric chain extender has shown increases in melt viscosity, IV, and strength similar to that for solid-state polymerization.
Compounders can benefit from the lower moisture sensitivity and improved hydrolytic stability, as well as augmented compatibility between other types of plastics such as PC/ABS and PET/Nylon. The additive''s benefits for materials, like improved melt strength, are applicable for sheet extrusion, fiber spinning, and extrusion blowmolding applications.
The polymer extender causes some long-chain branching, but is said to have significantly reduced any tendencies towards gel formation in the final material. Clariant Additive Masterbatches, Winchester, VA, USA; +1 540-665-1865; www.clariant.masterbatches.com; Johnson Polymer, Sturtevant, WI, USA; +1 866-290-5611; www.johnsonpolymer.com