Topic of the month August 2010

Figure 1: The novel polyamide Ultramid ® Endure is designed for operating temperatures of 220 °C. The material withstands temperature peaks up to 240 °C reliably. Source: BASF.

Metal Substitution: Plastics are on the Way

Each class of materials has its special characteristics: Metals are ductile and electrically conductive, ceramics are considered to be hard and temperature resistant, glasses provide transparency and plastics convince with low densities and good processabilities. These few examples are enough, to explain the dominance of certain materials for certain applications.
Due to changing requirements of the market, massive shifts concerning the material selection will occur in the future – this applies equally to standard applications and to high-tech applications. Possible reasons for this trend are changes in the raw materials situation as well as the increasing demands for material and energy efficiency. In particular, the practicability of intelligent lightweight design concepts, the reliable performance of complex property profiles and the ability for integration of multiple functions are increasingly becoming the focus of the manufacturing and construction engineers. These developments also match with the area of interest of the trade fairs wire and Tube. The exhibitors represent their product ranges of possible solutions and innovations for future product generations in advance. In this context recent developments in the field of innovative plastic materials convince due to the possibility to substitute metals in various applications.

Heat Resistant Plastics in Engine Construction

Especially in the field of vehicle construction intelligent material concepts are increasingly required in order to realize ground breaking solutions in the whole complex of energy efficiency and sustainability. Innovative lightweight construction concepts – for example on the basis of advanced plastics – will play a decisive role in the future. In this area solutions need to be found, which will cover the very high thermal requirements in the engine bay reliably and economically viable. Scientists of BASF developed a new polyamide based material called Ultramid® Endure. Ultramid® Endure is a glass-fiber-reinforced polyamide, which combines an excellent thermal aging resistance with the good processability of conventional PA 66. The new composite material resists constant temperatures up to 220 °C easily and withstands temporary peak temperatures of 240 °C reliably. With this development, the application range of polyamides is extended into the high temperature range of polymer materials. The increase of the thermal property profile was made possible utilizing a new stabilization mechanism, which forms a protective sealing on the material surface, which permanently protects against oxidation. Possible applications for this composite material are numerous components of charge-air ducts, such as resonators, charge air conduits and throttle valves.

Carbon Nanotubes make Plastics Conductive

Figure 2: Chemical resistant element for high-performance spiral conveyors made of plastic composite material. Source: TU Chemnitz, Arndt Schumann.

Scientists led by Dr. Holger Althues from the Fraunhofer Institute for Material and Beam Technology in Dresden recently presented a method, which makes it possible to equip
plastic products with a conductive and antistatic surface directly during the forming process in the tool. Therefore the scientists use so-called carbon nanotubes (CNTs), which they can work into the upper surface area of the polymer material. Compared to conventional conductive additives, which are usually mixed into the plastic matrix, the material costs are very low. Only a few milligrams of carbon nanotubes are sufficient to equip a square meter of surface with an approximately 50 nm thick conductive layer. Besides the low price, the small amount of added material offers other significant benefits like the fact, that the mechanical and optical properties of the polymer remain almost unchanged. This is of high importance - particularly in the case of modifying transparent plastic materials. The achievable electrical conductivity is convincing. A material is considered to be not electrostatically rechargeable having a conductivity of 10-9 Siemens, the achievable conductivity with this method lies in the range of 10-3 Siemens, which is higher by orders of magnitude. Transparent electrodes or flexible optical components with integrated electrical functions are typical applications for this material development.

Plastics with high Chemical Resistance

Spiral conveyors play a major role in waste treatment, food technology, mining and in the chemical industry. Similar to the principle of an Archimedes' screw, spiral conveyors transport raw materials, intermediate products and waste of different nature and condition. So far, these transport systems are primarily produced from steel. During the transport of aggressive substances, various components and parts can start to corrode, due to high acid or salt contents. High repair costs and expensive downtimes are the unpleasant consequences for the operators. Engineers led by Arndt Schumann of the Technical University of Chemnitz have now presented a new type of modular plastic spiral, in order to prevent such problems reliably. "Most thermoplastics are resistant to salt and acid or other corrosive substances," explains Schumann the advantage of the realized material substitution. In addition, the modules can be produced economically by injection molding, whereby the processing of different types of plastics is possible. As a consequence, fibre reinforced plastics are favoured for the transport of heavy flowing and stare bulk materials. For rather easy-flowing media, such as plastic pellets or granular matter, cost-efficient mass plastics are more suitable.

Dr.-Ing. Christoph Konetschny
Material and Nano Expert

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