Automobile body panels

When X in formula 1-22 is about 100, the polymers are known as phenoxy resins. Although further molecular weight increase can be accomplished by reaction on the pendant hydroxyls in the molecule, commercial phenoxy polymers already have sufficient strength to be formed directly into articles. They would be in the finite-strength region of curve B in Fig. 1-1. (The major current use for these polymers is in zinc-rich coatings for steel automobile body panels.)... 

The laminate sheet is a flexible decorative sheet for use in surfacing an automobile body panel. The laminate revealed in this invention contains several layers, including clearcoat, tie coat, color coat, and adhesive layer. Clearcoat is formulated from polyvinylidene fluoride (to assure excellent weather resistance), tie coat is formulated from acrylic (good adhesion to both clear coat and color coat and weather resistance), color coat was formulated from PVC (see formulation in the above table) and adhesive was pressure sensitive acrylic formulation. 

Carbon fibers continue to be the main reinforcement materials in advanced composites (qv). The ability to manipulate their physical, chemical, electrical, and thermal properties makes carbon fibers suitable across a wide range of commercial applications, including military [aircraft and missiles (1)], structural [concrete reinforcement (2,3) and automobile body panels], sports equipment (golf... 

Biaxially oriented polymer sheet is now widely used in packaging. High- and low-density polythene are common and recently polypropylene has become a popular film material. Polypropylene film of this type is often laminated with polyester and aluminium and with polyester or nylon. Relatively thick oriented sheet PET is also being assessed for applications in automobile body panels. 

M Kallaur, Composition of automobile body panel materials . 

The ABS/PC blends were first introduced in 1967, but it took 10 more years before a large scale production of Borg-Warner s Cycoloy and Mohay sBayblend (on a license from Borg-Wamer) began. In 1981 blends of SMA with ABS (Cadon) and with PC (Arloy) were introduced by Monsanto and Arco, respectively. The first ABS/PA blends were developed in Borg-Wamer laboratories in 1961 and three years later the patent was granted. Twenty years later the company introduced the ABS/PA blend, Elemid for use in automobile body panels. One of the most successful PA I ABS is Triax -1000, invented in 1980 and introduced by Monsanto nine years later. 

Figure 8.46 Designing practice for automobile body panels. (Reproduced by kind permission of SAE, Warrandale, PA, USA)... 

The development of new polymer alloys has caused a lot of excitement in recent years but in fact the concept has been around for a long time. Indeed one of the major commercial successes of today, ABS, is in fact an alloy of acrylonitrile, butadiene and styrene. The principle of alloying plastics is similar to that of alloying metals - to achieve in one material the advantages possessed by several others. The recent increased interest and activity in the field of polymer alloys has occurred as a result of several new factors. One is the development of more sophisticated techniques for combining plastics which were previously considered to be incompatible. Another is the keen competition for a share of new market areas such as automobile bumpers, body panels etc. These applications call for combinations of properties not previously available in a single plastic and it has been found that it is less expensive to combine existing plastics than to develop a new monomer on which to base the new plastic. 

What are the advantages and disadvantages of using softened steel for body panels on automobiles ... 

Along with traditional plastics, composites are also becoming more widely employed. GM has traditionally employed fiberglass composites for the Corvette s body panels (now using carbon-fiber composites for some of these panels), but is now looking to use composites for the body panels of other automobiles. 

The necessity to lower the weight of automobiles in order to meet the 1985 government CAFE requirements of 27.5 mpg. has spawned the development of high modulus RIM polyurethanes and reinforced RIM (RRIM) to replace metal in fenders, door panels, trunk lids, etc. The RRIM polyurethanes are well suited for the external body panel application where structural requirements are at a minimum. In addition to significantly lighter weight in comparison to steel, the RRIM panels eliminate corrosion problems and improve resistance to damage. 

The development of PUR-SMC technology will lead to further possibilities for the replacement of steel in automobiles, as well as the replacement of some UP-SMC use where better impact resistance is desired. As more elastic, lower modulus PUR-SMC s are developed and higher and higher modulus RIM systems are developed, competition for the same application can be foreseen, especially external body panels for automobiles. It is to early for market predictions for PUR-SMC, but with successful developments a meaningful penetration into replacement for steel in automobiles can be foreseen by the late 1980 s. 

Because they are relatively expensive, epoxy polymers have not been used very widely as binders in PC products. Therefore, epoxy PC is used for special applications, in situations in which the higher cost can easily be justified, such as mortar for industrial flooring to provide physical and chemical resistance, skid-resistant overlays (filled with sand, emery, pumice, quartz) in highways, epoxy plaster for exterior walls (e.g., in exposed aggregate panels), and resurfacing material for deteriorated areas (e.g., in flooring). Epoxy PC reinforced with glass, carbon, or boron fibers is used in the fabrication of translucent panels, boat hulls, and automobile bodies [2,6],... 

There is an enormous industrial interest to combine the best properties of the different polymers by improving their compatibility, creating real alloys instead of partially or totally immiscible blends. Some of the early alloys e g. the ABS-PC (quite miscible) blend has been a great industrial success, reaching up to the body panels of American automobiles (e.g. Saturn of the GM). The task is to obtain the greatest possible interaction between the polymers to be mixed... 

The process of corrosion is a redox reaction. Consider the rusting of die body panel of automobiles. Certain parts of the object that are imdergoing corrosion act as if they were half cells. For the corrosion of iron, iron is changed to Fe ions. Which of the following best represents the area where this change occurs ... 

The built-in costs of corrosion of automobiles were identified as corrosion protection for steel body panels such as metallic zinc coatings, paint, adhesives and sealants, nonferrous metals, corrosion-resistant materials, rust-proofing heat exchanger components, mufflers, and tail pipe corrosion. The greatest impact on the cost of corrosion for automobiles was the adverse effect of corrosion on the cost of replacement of the automobile. Both the lO model and focused sector study showed that in both models the cost of replacement of the automobiles dominated the total cost and avoidable cost estimation. 

Use of aluminum in the place of steel has two benefits, such as the lighter nature of aluminum compared to steel and better corrosion resistance than steel. New designs and aluminum alloys have resulted in some automobiles made entirely with aluminum including the frame. Polymers have been used to a greater extent as body panels in place of steel. Polymer panels are both corrosion and dent resistant. Automobiles must be designed to use the polymer panels, as the panels do not aid in the structural rigidity of the automobile. 

The effect of changes in materials in automobiles that contained body panels made from carbon steel, steel pre-painted with zinc-rich primer, or steel coated with zinc/zinc alloy. The data in Table 4.38 were obtained from 5- to 6-year-old vehicles in 1985 and 1993. 

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