Automotive plastics

Plastics Engineering, Sept, 1995 by Victor Wigotsky

Without question, the U.S. automotive industry is fielding superb cars in the 1996 model year. In the context of pervasive competitive pressures, however, the dominant, dynamic efforts within the industry are the need of the OEMs to continue to drive down costs; to further refine the boundaries of their internal and external design efforts; to hone their relationships with suppliers in the quest for ever-greater efficiencies; and to fully understand and Tact to the challenges of a global economy.

This model year there are many continuing, carry-over uses of plastics, and many innovative applications. But plastics in automotive design, notwithstanding their constantly growing level of sophistication, are still far from reaching their market potential. New goals and advances in automotive technology keep pushing the frontiers of materials and processing science and challenging the existing capabilities.

In one example, John Fillion, manager, Organic Materials Engineering, Chrysler Corp., says that the requirements of new head-impact regulations could add to the cost of hard interior trim. One direction, to offset the cost increment, could be to eliminate secondary painting through use of molded-in color. Fillion reports that all the interior trim in Chrysler's new 1996 minivan line is molded of integrally colored polypropylene, and he anticipates that the same will happen for other Chrysler platforms.

The new head-impact regulations also are creating pressures for improvement in the material's low-temperature impact performance. Future growth, then, is linked to the ability to achieve higher property levels through material development that, it is hoped, would not impose added cost.

In addition, while plastics are continuing to gain momentum in automotive, Fillion foresees increasing pressures on Tier 1 suppliers and resin producers to reduce process variations, even given the many major achievements in recent years in process control, quality, and performance. He is looking, for example, for smaller ranges of variation in material properties, part dimensions, and residual stresses; in short, the vision and customer demands are for even more defect-free products. "The competition for quality keeps going up," Fillion says, "and while our suppliers are gaining greater voices as our partnerships with them get ever closer, these relationships also increase their required level of shared responsibilities. As the days of competitive bidding recede, we are reaching out more and more to our supply chain to minimize variations, to continue to enhance quality, and to be increasingly cost-effective."

A stable record

Frequent changes in materials occur from model year to model year, but the external vertical and horizontal body panels for the GM Saturn Division's seven models in three body styles--sedan, coupe, and wagon--have been remarkably stable. Since the advent of the three different sedan and coupe body styles in 1991, the Pulse polycarbonate/ABS doors, GTX PPO/nylon front fenders, and the steel roof, hood, and upper rear deck have remained the same. The two-model Saturn wagon was introduced in 1993 with similar vertical body panel materials and an SMC deck lid and roof The only major change in an external body part material from the original Saturns has been to a steel roof for the 1996 wagon.

In its showrooms and advertising, Saturn has been promoting the "no dings or dents" and no-corrosion benefits of the plastic body materials, and has found a high degree of customer interest and acceptance. The division anticipates a total production of more than 300,000 of the 1996 models

Nylon brackets

The first plastic exhaust hanger brackets ever used at Ford are of AlliedSignal Plastics' Capron 8267 BK102 nylon in the 1996 Grand Marquis/Crown Victoria models. Also, the first plastic speaker mounting brackets at Ford will utilize Petra 110 in 1996 models, and the Ford Escort/Tracer uses a new Capron transparent grade for its power steering reservoir. The Chrysler Jeep Wrangler's center high-mount stop light housing is made from Capron 8233G HS BK-106.

Among AlliedSignal's new products are its PaintFree Petra resins, available in a variety of colors, and produced with 100% recycled PET thermoplastic polyester, and Capron HPN high-productivity nylon resins. The company says the faster cycling resins feature excellent flow and a high crystallization rate that facilitates quicker setting.

AlliedSignal will complete expansion- a doubling of capacity--of its Chesterfield, Va., facility in October.

Wider molding windows

Two new grades of Amoco Polymers' Amodel polyphthalamide have recently been introduced. Amodel AS-4133 XHS, for use in power trains, vehicle control systems, suspensions, and electrical/electronic systems, is processable in conventional water-heated tools at 150 [degrees] F to 200 [degrees] F and can yield shorter molding cycle times. In addition to its high heat distortion temperature, the material has a wider molding window, and improved mechanical and impact properties. Its ability to crystallize in water-heated tools eliminates the need for higher temperatures to achieve optimum properties.