Material success

Material success

The largest event in the plastics calendar, K2007, ran recently in Germany. Lou Reade rounds up some of the highlights



Back in October, Eureka exclusively revealed details of a new technology being developed by plastics giant DuPont. At the recent K2007 event, the biggest exhibition in the plastics calendar, the company revealed more details of the technology – including its name.
Metafuse is the coating technology that DuPont says will allow it to treat plastic components to make them compete directly with metal parts.
DuPont and three nanomaterials partners – Canadian-based sister companies Morph Technologies and Integran Technologies, and US-based PowerMetal Technologies – will develop and commercialise a nanocrystalline metal/polymer hybrid technology that will be used to manufacture lightweight components.
“We are turning traditional plastic/metal hybrid technology inside-out with an innovative metal-over-plastic technology that brings a step-change in performance,” said Keith Smith, vice president and general manager of DuPont Engineering Polymers.
Metafuse uses a proprietary process to apply high-strength nanometal to plastic components, to create lightweight components with higher strength than magnesium or aluminium, but comparable stiffness.
It produces metals with grain sizes 1000 times smaller than those of conventional metals, to create an integral metal cladding with a nanocrystalline grain structure.

Sit down and be counted
While nanoparticles are often seen as delivering a future of high-tech products, one company has used such a material in a very traditional product: a chair.
But the Myto chair is no ordinary product. The cantilever chair – made entirely of engineering plastics – relies heavily of BASF's Ultradur High Speed. This is a grade of polybutylene terephthalate (PBT) whose properties have been enhanced by the addition of nanoparticles.
The added particles give the material a much higher flow, meaning it can be used to make much thinner parts. This allowed the chair to be made using thin, rather than thick, cross sections.
“Even though the chair is manufactured as a monobloc and has a sturdy frame, its net-like perforations integrated into the backrest and the seat give it a graceful appearance,” says BASF.
The interplay between the plastic formulation and the design of the injection molding tool gave the product its final shape and properties. It was important that the plastic had the right ratio of elasticity, stiffness and strength.
The chair was created by industrial designer Konstantin Grcic.
Another common engineering plastics – polycarbonate – has also been used in chair design. This time, its transparency was the key benefit. Italian office furniture manufacturer Emmegi used the Makrolon 3107 grade from Bayer Material Science (BMS) in the latest design of its One chair.
To implement the draft designs, it worked closely with the design specialist Activa, engineering component developer and injection molder Vivi and BMS.
As well as the transparent chair model, the designs for One included two opaque colour versions with high-gloss surfaces – one in bright white, the other in black.
“Our in-house colour technology enables injection moldings produced in large volumes to be given a wide variety of customised colors and special effects, such as surface brilliance, a metallic look or fluorescence,” said Ciro Piermatteo, colour technology manager at BMS.

Looking good in nylon
Polyamide – or nylon, to use its less scientific name – is one of the most versatile engineering polymers, and a number of suppliers have claimed various breakthroughs in their own materials.
The polymer is actually a family of materials, which have differing properties. But all are tough, with relatively high heat resistance and are often used to replace metal parts.
Rhodia Polyamide's Technyl Star AFX is a polyamide 66 that claims to bridge the gap between standard polyamide and more costly high performance plastics or metal solutions.
For example, the company believes it could compete with more expensive materials such as polyphthalamides, polyamide 46 or polyarylamides. The material can be reinforced up to 60% without affecting processing behaviour, claims Rhodia.
Large and complex parts, and those with thin walls and ribs, should benefit from using the material, whose superior flow in the mould leads to easier cavity filling (+50% compared to standard PA66) and superior surface finish. Other advantages include better part mechanical performance and less moulded-in stress.
Potential automotive applications include rear view mirror supports, gear components, wiper levers and structural parts for seat components.
At the same time, the company has introduced a computer aided engineering service for parts made from its PA66, which should lead to more accurate predictions of characteristics such as impact resistance. MMI – which stands for Multi-scale modelling, Mechanical calculation, Injection moulding simulation – could help to shorten development cycles.
In the calculation process, the advanced mechanical properties of the polymer matrix stored in the MMI database are combined with the glass fibre orientation defined by injection simulation software. This ‘map’ of mechanical properties is then transmitted to mechanical simulation software, like Ansys and LS-Dyna, in order to evaluate stresses affecting the part.
The calculation relies on high quality material data and on multi-scale modelling software Digimat-MF, developed by e-Xstream Engineering.
High speed crash testing is one area in which Rhodia has carried out detailed research, allowing it to create a performance database in these types of application.
There is also a range of improved flame retardant grades, including Technyl A 60G2 V30, which boasts high mechanical performance, flame retardant properties and high flow. It is designed to fit a wide spectrum of demanding electrical applications.
For automotive applications, DSM Engineering Plastics has introduced Stanyl Diablo, a new generation of PA46 resins with improved long term thermal stability. It can withstand more than 3,000 hours exposure up to 230°C with less than 15% loss in mechanical properties, says the company.
The resin is aimed at automotive under-bonnet applications, which are becoming more stringent. Requirements for under-bonnet applications are changing constantly. The use of smaller engines with higher turbo pressures and EGR (Exhaust Gas Recirculation) means that components such as air ducts, air intake manifolds and charge air cooler end-caps are exposed to rising operating temperatures.
Ton Vet, turbo systems application development manager at DSM, says: “Longer and better lifetime reliability of parts is possible because of the material’s low creep and its fatigue behaviour. Part design and function can be reached more easily.”
BASF has extended its High Speed range of products to polyamide, introducing three highly filled grades of PA66. A nanoparticle additive helps to improve the flow – in this case, by more than 100% according to BASF. The concept was introduced on the company's PBT material.
'High Speed' grades of Ultramid A3WG8 and A3WG10 are filled with 40% and 50% glass fibres, respectively, while an optimum-warpage A3WGM53 is filled with glass fibers and mineral.
The added nanoparticles also improve heat-ageing resistance at high temperatures. BASF says these are the only polyamides with such a combination of properties, and will be available for sampling in early 2008. Highly filled grades of PA6 are also being developed.

Faster chunky parts
ExxonMobil Chemical's family of fast cycling Santoprene thermoplastic vulcanisate (TPV) grades can replace thermoset rubber and thermoplastic elastomers (TPEs) in chunky applications such as plugs, bumpers, grommets and other industrial and automotive components. The new grades of TPV M500, available in three different levels of hardness, can be processed 20-30% faster, claims the company.
The company is also looking to improve awareness of the design possibilities of TPVs by highlighting them on a new website (www.materialexperience.com). The site includes a number of examples of products designed using TPVs, including a kettle and a toiletries dispenser.

Automotive elastomer
DuPont has extended its Vamac series of ethylene acrylic elastomers with a new family of grades called Ultra. One grade, Ultra LT, is designed to help car makers meet new and emerging needs for cost-effective, lower-emission powertrain systems. It has low temperature flexibility down to -40ºC and can be blended with other Vamac grades. It can be used in automotive hoses, boots and dampers at temperatures from -40 to 160ºC.
Ultra IP is designed to boost productivity through reduced scrap and improved hot tear resistance and cycle time. The high viscosity grade delivers improved high temperature properties for improved vacuum collapse resistance, says DuPont.

Polycarbonate competition
Eastman Chemical has has introduced a new co-polyester family called Tritan, which it expects to compete with polycarbonate in houseware and appliance applications that require greater resistance to dishwasher systems.
The heat-resistant co-polyesters can be moulded in existing tooling used for polycarbonate resins. But their lower moulded-in stress means they can be processed at lower temperatures and without the need for a post-moulding annealing process, claims Eastman, leading to shorter cycle times. A 2% lower specific gravity means more parts can be obtained from every tonne of material.
US-based Camelback is already planning to use the resin in its BetterBottle water container that launches in 2008 as a replacement for polycarbonate.

Author
Tom Shelley

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