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Six of the best for applications that regularly get a caning

05 January 2010

Six new copolymer resins from the Lexan portfolio are claimed to break the mould when it comes to delivering top performance across a wide variety of demanding applications. Les Hunt investigates

Plastics are certainly put to the test these days and we tend to take their performance for granted in a variety of applications, from the mobile phone we casually toss to one side to automotive exteriors that are put to the test in all weathers. Fortunately, the polymer scientists have remained one step ahead in terms of innovation and new material introductions seem to presage the latest cutting edge designs, while offering cost and processing benefits.

SABIC Innovative Plastics has developed a portfolio of extreme performance polycarbonate (PC) copolymer resins in its Lexan range. The fruits of more than a decade of polymer science, this new high-end resin portfolio gives customers greatly expanded design options and materials with which to differentiate their products and increase their overall productivity and profitability.

The six new Lexan copolymers, including HFD, XHT, FST, DMX, SLX, and EXL resins, push the boundaries in terms of extreme high heat resistance, excellent flow/ductility, virtually unbreakable impact strength, scratch protection, flame-smoke-toxicity performance and UV protection. In addition to these performance parameters, you also get some eye-catching aesthetics into the bargain, as Bala Ambravaneswaran, product marketing director, Lexan Copolymer Resins, explains:

“Our expanding portfolio of Lexan copolymers clearly underscores SABIC’s’ leadership in creating innovative new thermoplastics to address diverse and evolving customer needs. To break new ground in performance, we moved away from incremental modifications and introduced radical new monomers in the resin chemistry. This approach has resulted in some unique and best-in-class properties. We have our finger on the pulse of the industry; we continually read the vital signs and we know what our customers require to excel and grow.“ Let’s take a look at the new Lexan offerings, their properties and target applications.

The new resins
HFD - These new copolymers provide the best of both worlds: high melt flow without traditional decreases in toughness and improved ductility without impacting melt flow; an added plus is their high clarity and excellent mechanical performance. Higher flow and ductility enable designs with thinner walls and sharp corners without a risk of cracking when released from the mould.

In addition to the high optical clarity, key performance features include low birefringence (double refraction); low-temperature processing permitting the use of heat-sensitive additives; high ductility at temperatures down to –40oC; high flow for Class A surface finish of glass-filled materials, and bio/green content.

Typical applications include camera lenses, medical housings, high-performance safety eyewear and face screens, and bezels for consumer electronics and appliances.

XHT - Providing highest performance for extreme heat conditions, these grades address customer aspirations for flame-retardant PC-based materials in the temperature range of 140oC to 195oC. They offer exceptional clarity and colour stability over a long life span, and provide greatly improved flow and impact compared with other high-heat capability PCs.

XHT resins are resistant to cracks and haze under metallisation; offer some 30% greater flow length compared with competitor materials, and are resistant to yellowing when exposed to UV over long periods. Target applications include auto bezels, reflectors and lens covers, industrial lighting shrouds, electrical components and fuses.

FST - these resins are claimed by SABIC to be the first transparent materials to meet the flame-smoke-toxicity requirements of the aerospace industry – without requiring a waiver. They provide a level of chemical resistance that is superior to that of standard PC materials, and can be coloured in a range of high-chroma hues, including bright whites. In addition to their ductility, UV stability and low weight (a property of great value to manufacturers of aircraft interior trim components), these resins comply with FAR 25.853a and 25.853d requirements and the OSU 55/55 standard.

DMX - These materials provide exceptional scratch resistance without the need for costly and time-consuming secondary coating operations. Their surface hardness is 2.5 times better than that of standard PC (‘pencil hardness’ H). Furthermore, they provide far greater impact resistance than traditional acrylics such as polymethyl methacrylate. DMX resins offer moisture and oxygen barrier properties and their chemical resistance extends to tolerance of ammonia. Among the target applications are keypads and touch screens, bezels for consumer electronics and lenses. In addition, these resins are suitable for the production of co-extruded film and sheet materials, to provide scratch resistant barriers for a whole range of vulnerable surfaces.

SLX - SLX copolymer resins deliver superior UV resistance that helps minimise yellowing and embrittlement. Instead of traditional UV absorber additives or coatings, this technology features a proprietary molecule that creates a protective layer over the resin. The material offers improved clarity, colour and gloss over the lifetime of the product, toughness and chemical resistance. Products manufactured in this material are unlikely to require protective coatings. Among the target applications are outdoor lighting products, meter windows, automotive bumpers, bonnets and trim.

EXL - Delivering extreme impact resistance even when subject to extremes of heat and humidity, these materials enable designs with thin walls, sharp notches and steep draft angles without compromising strength and stiffness. These are among the most ductile of SABIC’s new PC resins and are compatible with the VisualFX range of aesthetic finishes, and many types of filler. Bio-compatibility and ease of recycling are also quoted for the EXL range.

These properties offer suitability for a wide range of outdoor applications, including electrical enclosures, exterior automotive trim, personnel safety equipment and medical devices. A new design guide for Lexan EXL copolymer resins has just been published and is available from the SABIC website.

The six Lexan copolymer resins described in this article will soon be joined by new copolymers based on this technology, which are currently in development.

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