Market Snapshot: Automotive exteriors 20159

As this nation of car lovers celebrates such milestones this year as the 50th anniversary of the original “plastic” car—the Corvette—we are reminded of the continued importance of auto exteriors to a car’s popularity. Automotive exteriors are increasingly an arena for plastics, and many components are molded using new materials and techniques such as inmold painting and decorating to add pizzazz while reducing costs to manufacture.

A study released last year (“Dynamics of Auto Exteriors: Plastics, Elastomers, Coatings”) by Business Communications Co. Inc. estimated the automotive exterior plastics market at almost 1.2 billion lb, and that is expected to grow at an annual average rate of 3% to almost 1.4 billion lb by 2006. This estimate includes five major resin/elastomer groups: thermosets, TPEs, engineering resins, commodity thermoplastics, and alloys and blends. Of these, engineering resins make up the largest market with a volume of 365 million lb and a corresponding market share of about 30%, and are expected to grow 4.4% over the forecast period.

According to the study, bumper systems applications are clearly the area where plastics have made the most significant penetration in exteriors, with TPOs being the dominant material. Side trim and moldings, transparent lenses, headlamp/signal light housings, and body panels are the other key areas where plastics have surpassed metals.

Those in the trenches are already seeing some of the study’s projected growth. John Hooker, controller for Blackhawk Automotive Plastics Inc. (Salem, OH), says that following a slow July and August when OEMs pulled back inventory, things have started to pick up. “The pipeline has been drawn down a bit, so we’re looking positively toward the near term,” Hooker says. “That’s a correlation to the economy in general.”

Mark Ellis, senior materials design engineer at Nissan’s technical design center in Europe, says in an article (“Automotive Plastics Firms Urged to Focus on Exteriors,” Jan. 22, 2003, www.omnexus.com)), “While plastics won the battle for automotive interiors in the latter half of the last century, they need to do it in the new century for exteriors.” The article notes that Nissan is increasingly outsourcing its plastic parts but is retaining its in-house bumper molding in the U.K. and Spain.

In addition, the company is looking for plastic exterior panels that meet Class A surface and painted color matching requirements that are achieved with steel panels.

Color Without Paint

Some of the new technologies driving the automotive exterior business include molded-in color and nanocomposites. Regarding the latter, Hooker says Blackhawk is taking part in a nanocomposite program with General Motors. Additionally, “we’ve been involved with [inmold paint] through developmental programs,” Hooker notes. “There’s a place for traditional exterior painting, but there are some applications where the inmold paint is an excellent alternative.”

A number of material suppliers are answering the call for reduced costs and faster time to market by providing resins that do not require painting. (For more on this trend, see August 2003 IMM.) DuPont Bexloy W permits molded-in color for wheel flares at a 50% cost savings over painted parts. The injection molded wheel flares require an attractive, durable appearance, strength, and scratch resistance. Bexloy W thermoplastic modified ionomer resin is engineered for injection molded exterior automotive applications, and is designed for use where the principal requirements are a combination of relative low cost plus attractive, durable appearance.

Thermoplastics are competing with thermosets more and more for body panels, fenders, and other major exterior parts. SMC is currently the most widely used material for many of these parts.

DuPont also introduced new grades of Rynite PET that combine the structural capabilities of reinforced engineering plastics with that of a high-gloss painted surface. The big advantage is that the molded parts provide a Class A surface finish while requiring less finishing than SMC or metal parts.

Like resins with molded-in color, inmold decoration/paint is projected to catch on in a big way for automotive applications because of the cost savings over painted parts, according to Greg Adams, general manager of global marketing for GE Plastics. GE’s Lexan SLX PC film is designed for inmold decoration of injection molded parts to replace paint on panels requiring a Class A finish. The film is first thermoformed into the required shape and then placed in the mold, where the resin is injected in the usual process. The resulting part has excellent color stability and improved scratch and chemical resistance.

The Dodge Neon features no-paint, high-gloss bumper fascia using a four-layer film with extruded-in color that includes layers of color-matched ionomer, a UV-stabilized clear coat from A. Schulman, a PP copolymer backing layer, and an adhesive layer from ExxonMobil. This is thermoformed to the required shape and then placed into an injection mold, where a PP copolymer is injected behind it.

Another example of an application that is saving molders and OEMs time and money is a hubcap made from DuPont’s Zytel nylon 6/6 for nondriven truck axles. This is reportedly a first-of-its-kind replacement for aluminum and steel. The hubcap contains two molded-in inserts, a transparent nylon sight window for oil level inspection, and an aluminum flange for bolt mounting to the wheel hub.

DuPont says the material provides impact resistance, oil resistance, low creep, and good strength. The hubcaps have improved leak resistance because the insert molding technology produces a fusion bond between the sight window and body; costs have also been reduced through a one-step assembly process with no screws and fewer parts.