Body panel , polyurethane-RRIM

For this case study, a vertical body panel such as that being molded of glass reinforced polyurethane-RIM (PU-RRIM) for the Pontiac F1ero fenders and door panels was chosen. The average projected surface area for a typical fender and door panel 1s about 750 sq. 1n. and 1,000 sq. 1n. respectively. The fender was selected for this stu[Pg.16]

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. 

RRIM polyurethanes are widely used for body panels. Bayflex 150 (of Bayer) was chosen by Pontiac for its 1987 Fiero, a well-publicized all-plastic car. The car s panels hang from a metal space frame. Bayflex 150 is used on vertical panels while the bonnet and roof are made of sheet molded components. Bayflex 150 is said to offer a number of advantages (improved thermal stability, stiffness, impact resistance, and dimensional stability) over conventional ureas without their processing limitations. 

The polyurethanes and polyureas may be formulated to be flexible or rigid, solid or foamed. Fillers and/or reinforcing agents (for example, glass fibers or flake) may be added to one or both components (in which case the process is sometimes known as RRIM—reinforced RIM). A major application of RIM is to produce energy-absorbing front and rear ends and body panels for automobiles. Cycle times of two minutes or less are feasible for such large parts. 

Nevertheless, auto makers and adhesive formulators have been able to work around these difficulties and structural plastics are being used in increasing amounts. For example, the hood of the 1984 Pontiac Fiero consists of two plastic panels adhesively bonded together. The RRIM panels on the car s doors are also adhesively bonded. Ford has recently built an experimental car in which the body, chassis, and power train are made of graphite-reinforced composites. Almost the entire assembly, including primary load bearing joints, was bonded with a polyurethane structural adhesive in place of mechanical fasteners or welds. ... 

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