POLYMERS IN AUTOMOBILE APPLICATIONS

The Direct Methanol Fuel Cell, DMFC, (see Fig. 7-6 in section 7.2.2.4.) is another low temperature fuel cell enjoying a renaissance after significant improvements in current density. The DMFC runs on either liquid or, with better performance but higher system complexity, on gaseous methanol and is normally based on a solid polymer electrolyte (SPFC). R-Ru catalysts were found to produce best oxidation results at the anode, still the power density is relatively low [5, 29]. Conversion rates up to 34 % of the energy content into electricity were measured, an efficiency of 45 % is expected to be feasible in the future. SPFC in the power order of several kW to be used in automobile applications are currently in the development phase. 

Similarly the disadvantages of PC are the stress cracking and chemical sensitivity. Stress cracking can be treated as a part of impact properties and a simple solution may thus be addition of ABS or ASA. On the other hand, to improve the solvent resistance—a property that is particularly important in automobile applications—a semicrystalline polymer may be added. From Table 4.37, it is apparent that TPEs (e.g., PBT, PET) could provide that property, but they also lack warp resistance and impact strength. Hence an ideal blend for automobile application based on PC and TPEs should be impact modified with, for example, an acrylic latex copolymer. A schematic of preparation of this type of toughened blend introduced by GEC-Europe in 1979 under the tradename Xenoy is shown in Figure 4.41. 

The use of polymers in automobiles has increased dramatically over the last 100 years. Particularly significant gains were made within the last two decades. Figure 17.1 shows the dramatic increase in the polymer content in a typical vehicle over recent years. These materials provide increased comfort, better aesthetics, safety enhancements, and environmental benefits over the conventional materials they replaced. This chapter will discuss where these materials are used and the environmental benefits they provide in such applications. 

Polymer-alloy technology is important, and has the potential bringing polymer materials in automobiles applications, together with fiber reinforcement technolgy. The technolgy is to blend or mix several kinds of polymers while controlling micro-structure. This provides polymer blends or mixtures with the desired properties. 

One technical difficulty that does beset recycling is that in many applications a variety of polymers are employed together in a complex way. It therefore becomes essential to distinguish between the various types of polymer in order to separate them. One system proposed (but not yet introduced anywhere in the world) is for the individual polymer components of complex articles such as automobiles to be identified using computer-scannable bar codes on each individual polymer component. 

We use a variant of flexural testing to measure a sample s heat distortion temperature. In this test, we place the sample in a three point bending fixture, as shown in Fig. 8.6 b), and apply a load sufficient to generate a standard stress within it. We then ramp the temperature of the sample at a fixed rate and note the temperature at which the beam deflects by a specified amount. This test is very useful when selecting polymers for engineering applications that are used under severe conditions, such as under the hoods of automobiles or as gears in many small appliances or inside power tools where heat tends to accumulate. 

We use variants of profile extrusion to produce tubing -with diameters of less then 1 mm and pipes with diameters exceeding 1 m, Wall thicknesses can vary from a few tens of micrometers up to several centimeters. Extruded window and door frames are more complex than pipes. Such profiles are largely hollow with internal ribs and fins that reinforce and divide the interior into two or more channels. We use solid rubber profiles in applications such as door seals and windshield wipers. We can produce foamed extrudates by incorporating a blowing agent, such as butane or carbon dioxide, into the polymer in the molten state. As the polymer exits the die, its internal pressure drops and the dissolved gas expands to form bubbles within the product. Examples of foamed extrudates include pipe insulation and automobile door gaskets. 

Among the spectrum of melt-spinnable fibers such as polyolefins and nylons, PET stands at the upper end in terms of crystalline melt temperature and glass transition temperature. This provides superior dimensional stability for applications where moderately elevated temperatures are encountered, e.g. in automobile tires or in home laundering and drying of garments. The high thermal stability results from the aromatic rings that hinder the mobility of the polymer chain. 

Numerous demonstrations in recent years have shown that the level of performance of present-day polymer electrolyte fuel cells can compete with current energy conversion technologies in power densities and energy efficiencies. However, for large-scale commercialization in automobile and portable applications, the merit function of fuel cell systems—namely, the ratio of power density to cost—must be improved by a factor of 10 or more. Clever engineering and empirical optimization of cells and stacks alone cannot achieve such ambitious performance and cost targets. 

Do you think that daily life would have been easier and colourful without the discovery and varied applications of polymers The use of polymers in the manufacture of plastic buckets, cups and saucers, children s toys, packaging bags, synthetic clothing materials, automobile tyres, gears and seals, electrical Insulating materials and machine parts has completely revolutionised the daily life as well as the industrial scenario. Indeed, the polymers are the backbone of four major Industries viz. plastics, elastomers, fibres and paints and varnishes. 

These new synthetic rubbers were accessible from potentially low cost raw materials and generated considerable woddwide interest. For a time, it was hoped that the polysulfide rubbers could substitute for natural mbber in automobile tires. Unfortunately, these original polymers were difficult to process, evolved irritating fumes during compounding, and properties such as compression set, extension, and abrasion characteristics were not suitable for this application. 

Fuel cells are the primary technology that will advance hydrogen use (DOE, 1998). Fuel cells are important as they are one component of a system that can efficiently produce electricity for many applications (Jacoby, 1999). It is also widely accepted that fuel cells are environmentally friendly (Hirschenhofer, 1997). Low temperature fuel cells, such as polymer-electrolyte-membrane (PEM) fuel cells, are being considered for many applications including electric power generation in commercial and residential buildings, automobile applications and... 

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