Plastic Fantastic

Global demand for polycarbonate (PC) resin continues to grow strongly in the high teens, with consumption now approaching an annualized 3 million tonnes worldwide. This equates to approximately half the annual 6 million tonnes of global demand for acrylonitrile butadiene styrene (ABS), with which PC is often compounded. Growth drivers for PC include automotive, construction, electronics and medical, and suppliers are targeting these segments with specialized grades to maximize performance.

In the medical segment, "The mere fact that our aging population will generate an increase in the demand for medical care, coupled with constant improvements to healthcare systems in developing countries, will contribute to increase demand for PC. In addition, new fields of application for polycarbonates are now emerging from areas such as genetics and biotechnology and from innovative treatment methods," explains Markus Krieter, a medical technology expert from the polycarbonates business group at Bayer MaterialScience. A recent application of a Bayer PC grade was in pressure-resistant ampoules for the Injex needle-free injection system.

GE Plastics, meanwhile, recently introduced two new autoclavable biocompatible polycarbonate grades-Lexan HPX4 and HPX8R-for medical applications (January 2006 MPW). A third Lexan medical grade, HPS7, is radio-lucent (invisible to x-rays) and was employed by Rigid Orthopedics in its Clear Wrist Fixator. The grade also passed the application requirements for impact resistance, clarity, lightweight, and gamma sterilization capability.

For automotive applications, Bayer MaterialScience recently debuted Bayblend DP T65 TX, a PC/ABS alloy for thin-wall applications, boasting 15% better flow than current Bayer PC/ABS grades without compromising other properties. Bayer MaterialScience sees great potential for using the new material, particularly in vehicle interiors and for coated components for vehicle exteriors. Bayer's Makrolon AG 2677 PC, meanwhile, was employed in the "teardrop" roof of a concept car at the Geneva Motor Show held in March this year. The entire roof dome was molded in a single shot from the automotive glazing grade.

Construction represents a promising area for PC, where it competes with such materials as acrylic and PVC. In a recent major project, the largest round roof of its kind in the world-that of the massive new Shanghai South Railway Station- was constructed of Lexan PC sheet from GE. The roof uses 55,000m2 of GE's Lexan multiwall sheet.

GE sheet was also employed in the boarding platform roof. More than 25 tonnes were employed to construct the six 360m-long, parallel roof sections. Bayer MaterialScience, Leverkusen, Germany; +49-214-30-1; www.bayermaterialscience.com; GE Plastics, Pittsfield, MA, USA; +1 413-448-7383; www.geadvancedmaterials.com

New grades go head-on versus PC in headlights

Polycarbonate has a long history of use in automotive lighting applications, but a number of suppliers of other thermoplastics are striving to snatch market share in these parts.

For instance, engineering thermoplastics supplier Solvay Advanced Polymers LLC has introduced two materials it says are optimal for use in highly reflective automotive forward lighting applications (headlamp bezels and reflectors, fog-lamp reflectors, and park-and-turn reflectors). Both materials allow for direct metallizing.

One grade, Udel LTG-2000 polysulfone (PSU), is useful to temperatures up to 175°C; the second grade, Radel LTG-3000 polyethersulfone (PES), is suitable for use in temperatures up to 205°C. Both are aimed at toppling the entrenched materials, polyetherimide (PEI) and PC/PEI blends. Both Solvay materials can be directly metallized, as opposed to offline metallization and its associated costs.

According to Solvay, its Radel LTG-3000 PES beats many PEI grades on temperature resistance and 50% higher impact resistance, while offering a 33% increase in melt-flow rates. "This increase in flow allows engineers to reduce wallstock by at least 25% while maintaining toughness," says Matt Howlett, global market manager for lighting materials at Solvay Advanced Polymers. "The first time you put the LTG materials in a tool, you'll appreciate the difference-pressures will drop, material will flow better, and you'll fill out the part with less molded-in stress."

Udel LTG-2000 polysulfone is Solvay's champion versus high-temperature PC and PC/PEI blends. Solvay says its PSU has greater temperature resistance than most high-temperature polycarbonates and PC/PEI blends. The new lighting-grade polysulfone also has significantly higher flow rates than these competitors.

Solvay recently invested $50 million to expand its Marietta, OH facility in order to increase its sulfone-based thermoplastics capacity.

In an interesting application development and PC replacement scenario, headlamp bezels for the new Ford Transit are the first instance this part has been developed and molded in Turkey. Turkish electrical components supplier Mako, owned by Magnetti Marelli (Italy), molds the bezels using Zytel 103 HSL, a heat-stabilized nylon 66 from DuPont. Polycarbonate is the entrenched bezel material.

The parts were first premiered at the Commercial Vehicle Show in Birmingham, England in late April. Mako applies a silver-metallic paint bezels; no primer is needed. Solvay Advanced Polymers LLC, Alpharetta, GA, USA; +1 770-772-8200; www.solvayadvancedpolymers.com; DuPont, Wilmington, DE, USA; +1 800-441-0575; www.plastics.dupont.com

PC stands up to sterilization

Applicable in medical packaging applications, a new polycarbonate (PC) film is able to withstand gamma and E-beam radiation used in sterilization without yellowing. Makrofol LP 209 uses an additive system to tolerate the sterilization technologies that are increasingly displacing ethylene oxide gassing, which requires heat and can leave residue.

Potential applications include titration plates, instrument boxes, and implant packaging, with the film available in standard thicknesses between 175-500 micrometers. Makrofol LP 209 satisfies ISO 10993 Part 1 biocompatibility requirements, which regulate materials in contact with body fluids and tissue for up to 30 days. In addition, the material meets US-Phamacopeia Class VI biological compatibility standards.

In another medical PC development for the manufacturer, following its success within the marketplace, a PC grade has been granted commercial status, earning a new moniker: Makrolon Rx1452.

Offering strength, clarity, and processability, the PC meets FDA-modified ISO 10933, Part 1 requirements for biocompatibility in certain tints and colors. Makrolon Rx1452 PC is said to be especially suited for difficult-to-fill molds and parts with shallow draft angles, like cylinders, thanks to an internal mold-release technology. Normally, many PCs can require the use of a spray-in mold release to get components to eject cleanly from the mold, but the use of such chemicals in cleanroom environs of medical applications, is, of course, not an option. The material is also said to help decrease cycle time, and allow for automation of demolding, potentially reducing direct-labor costs. Bayer MaterialScience LLC, Pittsburgh, USA; +1 412-777-2000; www.bayer.com.

PC glazing finds windshield application

Moving beyond side windows or sunroofs and introducing the latest generation of its Exatec 900 glazing paired with Lexan GLX polycarbonate (PC), Toyota Auto Body used the material system for windshields in nine electric vehicles deployed at the 2005 World Exposition (Aichi, Japan).

Exatec 900, which is the latest iteration of the original Exatec 500 system launched in 2003, includes 900vt (vehicle top) and 900el (electroluminescence) technologies. The polymer-based system reportedly reduced weight by 40%-50%, while offering wiper performance and extended life.

Exatec's (Southfield, MI) product includes a PECVD (plasma-enhanced chemical vapor deposition) coating for glass-like abrasion, wiper capability, extended weathering, scratch resistance, and a bonding surface. Silicon hard coating is included for UV protection, with inks and pastes used for the purposes of decoration and functionality. The GE Lexan or Bayer Makrolon PC is the final element, including additives and dyes. The system also includes the SHX proprietary weather interlayer, which, using a predictive weathering model program, was projected to withstand more than 10 years of outdoor exposure. Exatec is a 50:50 joint-venture business established by Bayer MaterialScience (Leverkusen, Germany) and General Electric Advanced Materials (GEAM; Pittsfield, MA) in 2003. Bayer points out that PC has already replaced glass in more than 90% of automotive headlamps, and its use in applications like the louvered sliding sunroof of the Mercedes Benz A-class bodes well for the future automotive integration. GE Advanced Materials, Pittsfield, MA, USA; www.ge.com.

Carmakers pass on glass

Polycarbonate (PC) window glazing is fast moving from novelty product to mainstream application. Weight savings and parts' integration, the hallmarks of plastics in their replacement of so many traditional materials, here also are seen as key attributes. Safety also plays a significant part in the transition.

Exatec, the PC glazing technology joint venture formed in 1998 between Bayer MaterialScience and GE Plastics, inMarch introduced a new product, Exatec 900el, which would allow injection molding of an electroluminescent interior light-band in different colors directly integrated into the perimeter of the transparent polycarbonate car roof.

Exatec's research focuses on the manufacturing processes that automotive systems suppliers need to design, mold, print decorate, UV protect, plasma hardcoat, bond, and assemble windows. The company licenses its technology.

The electroluminescent roof was manufactured using the proven Exatec 900 technology and the light-band was applied directly onto a film. The illumination intensity conforms to the legal regulations and does not exceed the allowed level; drivers and passengers can adjust the brightness of the interior lighting.

The electroluminescent light-bands consist of a stack of layers that work, in principle, like a capacitor. Between a front and a rear electrode there is a layer of luminescent pigment, which, together with the encapsulating product, forms the insulating layer (dielectric). When a voltage is applied to one of these electroluminescent cells, the color pigments begin to shine due to the current.

Most current sunroofs are made of either tempered glass or standard laminated glass. Single-layer tempered glass is the traditional, low-cost alternative but is losing favor due to safety concerns and its heavy weight. Greater impact resistance is provided by standard laminated glass with a thin polyvinyl butyral (PVB) film sandwiched between the two sheets of glass.

An alternative solution proposed this spring by supplier DuPont Glass Laminating Solutions (Troy, MI) is its Spallshield thermoplastic composite for use in vehicle sunroofs. Spallshield is a composite of PVB and polyethylene terephthalate (PET), with an additional antiscratch coating on the PET. The composite can be applied to a single, standard layer of glass using traditional glass lamination processes.

Spall means to break into small splinters or fragments. DuPont markets the material as an alternative to pure organic plastic glazing or other existing glass-glass type laminates. The technology was specified in sunroof systems on the new S- and R-Class vehicles from Mercedes-Benz, introduced in the latter half of 2005. DuPont's technology is new for mainstream automobiles, but has seen nearly three decades of use in bullet-resistant and hurricane glass.

Applied to a single layer of glass, Spallshield provides up to eight times the impact performance versus standard laminated glass, according to DuPont, while offering weight savings to 30%. According to the supplier, the sunroof market is growing at 10%-15%/yr rates. Weight savings have become a dominant issue in sunroof design as these parts, too, grow ever larger with panoramic roofs the current rage.

The supplier says the technology is being considered for 14 other vehicles, for sunroofs, sidelights, and backlights. Exatec LLC, Wixon, MI, USA; +1-248-926-4200; www.exatec.de; DuPont, Wilmington, DE, USA; +1-800-441-0575; www.plastics.dupont.com