Plastics vs Automobile Industry

Delphi's TPO-skin instrument panel provides a weight reduction of 10%. Delphi's recycling process allows for in-plant, closed-loop recycling of 100% offal directly back into the skin. From the roof frame to the door liners to the upholstery components, numerous applications on the Audi TT utilize Bayer materials.

Traditionally, instrument panels were made from several separate components that needed to be painted and that were all held together by a steel supporting beam that lay behind the panel. Today, thanks to modern plastics technology, instrument panels are made of ABS, ABS/PC alloys, PCs, PP, modified PPE, and styrene maleic anhydride (SMA) resins. The use of these plastics enabled the elimination of the steel support beam in some cases, providing savings of both cost and weight. Wholly integrated single-piece units can be manufactured from all-urethane and all-PP resins for a seamless instrument panel with reduced NVH levels, molded-in color, and cost and weight savings.

Delphi Automotive Systems' TPO skin instrument panel represents a new generation of TPO product technology, an instrument panel skin molded from TPO rather than from a PVC compound. TPO is a material made by combining rubber with PP and has been used in automotive applications for decades. PP is the lightest and lowest-cost form of plastic. Rubberized PP is classified as TPO when the material contains at least 20% rubber.

Delphi applied its TPO skin technology to the upper and lower panels of the 2000 Pontiac Bonneville and the 1999 and 2000 Mercedes-Benz M-Class, providing a panel with a weight reduction of 10%. The product was created by a partnership between Delphi, Mercedes-Benz, toolmaker D&E Corp., and Mytex Polymers, a partnership of ExxonMobil Chemical Co. and Mitsubishi Chemical Corp. Delphi overcame the challenge of offering deep draw capability with TPO, meaning that the material can be vacuum-formed to meet complex shape and contour demands. The material enables hidden airbag doors without seam read-through and airbag deployments without fragmentation at low temperatures.

Delphi uses water-based primer and topcoat systems on its TPO components, reducing ozone-forming volatile organic compound emissions. Delphi's process for the TPO-skin manufacturing allows for in-plant, closed-loop recycling of 100% offal directly back into the skin.

When P.L. Porter Co. switched from metal to composite components on its automotive seat-reclining mechanism, the firm chose for its swing arm component Verton RF, a long glass-fiber-reinforced nylon 66 structural composite from LNP Engineering Plastics, that had the necessary compressive and tensile strength. A swing arm component is the seat-reclining mechanism actuated by a handle on the side of the car seat. It is a locking device that allows passengers to move the seat back and forth, and must be made of a high-strength material to support normal loads, as well as extra loads such as someone stepping on the handle. In a two-door car or truck, a lever is actuated to dump the seat forward to enable passengers to climb into the back seat. For the dump lever component, the firm chose Lubricomp RFL, a glass-fiber-reinforced lubricated nylon 66 composite also from LNP. The nylon dump lever has an internal lubricant that reduces friction and wear rates. By using the two composites, P.L. Porter was able to incorporate the seat dump within the reclining mechanism for about a third of the cost of the original part.

In the interior of the Audi TT, plastic components create the link between aesthetics and functionality. The door liners are made from the ABS polymer Lustran 2443 developed by Bayer specifically for this application. Because of its good flow properties, the complex geometries of the door trim panels were produced economically and without problem by injection molding. Indentations, handle recesses, openings for switches and speakers, and the various fastening elements could all be directly integrated. The manufacturer of the moldings is Seeber Systemtechnik KG. Due to its high-impact strength, the thermoplastic lining is unlikely to splinter, reducing the risk of injury to the driver and passengers in the event of a side impact. The material also bonds well with standard solvent-based and solvent-free laminating adhesives that are used to fix decorative facings. The center console of the TT is also made of Lustran, injection molded by Peguform Bohemia.

The A- and C-pillars and the roof frame are made of Bayblend, Bayer's PC-ABS blend. This plastic is noted for its consistent mechanical properties at low wall thicknesses. Polyurethane foam padding made of Bayer's Bayfill EA and produced by Thieme is built into particularly critical areas of the A- and C-pillars, the rear section of the roof, and the rear side-trim panels. In the event of a crash, force absorption by the padding is more or less equal over a wide deformation range so that even low component thicknesses will absorb impact energy.

M.A. Hanna Engineered Materials uses a nylon resin reinforced by both glass-fiber and mineral fillers for automotive cooling systems. The electronic throttle control mechanism on the 2000 Ford Transit was developed by Teleflex Automotive Group using DuPont's Zytel 33% glass-reinforced nylon 66 resin. NRI Industries' Symar-T contains up to 60% post-consumer rubber and is used on the lower radiator seal of the 1999 Jeep Grand Cherokee. Hexcel's composite leaf springs weigh up to 60% less than steel counterparts and absorb energy more readily. The RITec fan shroud assembly consolidates five parts into a single, blow-molded component. Rover's air-intake manifold made of glass-reinforced nylon 66 from DuPont reduces weight by 40%. Rover used nylon resins from BASF Plastics for the air-intake manifold on its 2-L, four-cylinder turbodiesel engine. Mark IV's thermoplastic manifold features a communications valve that allows the manifold to shift between its two plenums. Dana produces the thermoplastic rocker cover for Tritec's new 1.6-L, 4-cylinder engine. TI Group Automotive System's 2000x Smart Tank is an electrically managed fuel storage and delivery system that features a plastic multi-layer tank with a vapor barrier and in-tank computer. Permblok corrugated hose products for vapor lines are made of plastic in single- or multi-layer construction. Solvay's six-layer co-extruded HDPE fuel storage and delivery system.

Structural components require glass-fiber reinforcement for stiffness purposes, but during the injection-molding process the fiber orients with the flow of the polymer, which could lead to anisotropic shrinkage during cooling and warpage of the part. This problem is made worse where the flow path typical in large parts is more complex and long flow lengths are required. Although jigs can be used after molding to achieve part flatness, this can lead to frozen-in stress in the part, causing warping or early mechanical failure in service.

Nylon 66 resin is a widely used base polymer for under-the-hood components because of its balance of properties, such as good heat performance, resistance to oils and other chemicals, and toughness. However, like most semi-crystalline materials, nylon has a relatively high shrinkage, leading to larger differences in the flow/cross-flow direction for simple glass-fiber-reinforced materials. Cooling system designers working with M.A. Hanna Engineered Materials faced that problem during the design of a large cooling fan housing that required a reinforced nylon 66 resin. The large size of the part and the tolerances between fixing points demanded higher performance than could be delivered by a standard glass-fiber-reinforced grade. In this case, the solution was Bergamid PA66, a tailor-made material from M.A. Hanna that uses both glass-fiber and mineral fillers for the stiffness and reduced warpage that the cooling fan housing required.

The electronic throttle control (ETC) mechanism on the 2000 Ford Transit was developed and produced by Teleflex Automotive Group using DuPont's Zytel 33% glass-reinforced nylon 66 resin. The ETC, also known as drive-by-wire, consists of an all-plastic intermediate electrical control housing that encapsulates a wire lead frame, plastic outer housing/mounting bracket, and a plastic cover that is heat-staked in place. The ETC links the engine controls with two electrical signals: a limit switch that signals whenever there is no driver foot pressure on the pedal, and an integrated sensor that provides a variable acceleration/deceleration signal based on the position of the pedal. The new thermoplastic ETC pedal looks and feels like a standard mechanically linked pedal, and is considered the next step in continuing the growth of plastics in the automotive chassis segment that a 1999 Market Search Inc. automotive plastics report predicted will grow by 38% before 2009.

Responding to the growing need for recycled content in automotive materials, NRI Industries developed Symar-T, a hybrid polyolefin-based thermoplastic elastomer containing up to 60% post-consumer, tire-derived rubber. The material is used on the lower radiator seal of the 1999 Jeep Grand Cherokee, combining the benefits of rubber and plastic to cost-effectively cool airflow and improve grille appearance. According to NRI, 1,531,000 kg (3,375,000 lb) of Symar-T is used per year, removing 150,000 scrap tires from landfill waste.

Hexcel Corp.'s prepregs are fiber-reinforced resin systems that are cured under pressure to produce stiff yet lightweight structural components. According to the company, the energy-absorption and fatigue-resistance characteristics of the prepregs make them an ideal candidate for composite leaf springs. Composite leaf springs weigh up to 60% less than their steel counterparts, while absorbing energy more readily than steel and providing a more comfortable ride. Fatigue resistance is greater than with steel so that in the unlikely event of a fracture with composites, the failure would be gradual and identifiable, avoiding the sudden catastrophic failure characteristic of metal parts.

Composite leaf springs are noncorrosive and resistant to salt damage in winter climates as well as oil, gasoline, and battery acid. Unlike metal, it is unnecessary to coat them with protective anti-corrosion paint. Hexcel's composite leaf springs are molded into shape in a single operation. The prepreg process enables leaf spring designers to incorporate contoured shapes as a single part. The reduced part count and volume processing of composite leaf springs can provide added cost benefits to the manufacturer. Hexcel's prepregs for leaf springs are supplied with a uni-directional glass-fiber reinforcement and woven or multiaxial glass or aramid fibers. The pregregs are supplied in roll form and are cut to shape before being placed into a mold tool.

Making the switch from traditional injection molding to blow molding, McCord Winn Textron's RITec (reservoir integration technology) modular fluid-management system for the 2000 Dodge Durango/Dakota consolidated the radiator fan shroud, coolant reservoir, front and rear washer reservoirs, and the rear washer reservoir fill funnel into a single, blow-molded component. This component integration saved engine compartment space, eliminated a number of fasteners, reduced assembly floor space and time, and reduced vehicle mass by 0.5 kg (1.2 lb).

Montell supplied the PP resin, Pro-fax HMS, for the system, with tool and process design from Hobson Mould Works. Industrial Design Associates Inc. assisted in the final RITec part design and engineering recommendations, as well as the preliminary tool design. The inherent matte finish, heat-deflection temperature performance, and environmental stress crack resistance of the PP resin was critical in the selection of the material over high-density polyethylene (HDPE). The component's weight reduction was due in part to the unfilled Pro-fax HMS being 27% less dense than conventional 40% mineral-filled PP. The material provided blow-molding processability improvements over traditional blow-molding materials, such as higher melt strength and greater blow-up ratio, which resulted in a more uniform material distribution.

The BMW Group's new active air-intake manifold for Rover is made of Zytel, a glass-reinforced nylon 66 from DuPont. The component is Rover's first plastic intake system on a V6. Switching from aluminum to nylon reduced weight by 40% and costs by approximately 30%. The manifold offers reduced complexity while delivering significantly more torque than the passive aluminum manifold it replaces, incorporating MANN+HUMMEL's patented overmolding process using dissimilar materials to create all-plastic flap valves. The flap valves, the valve's frame, shaft, and flap are all formed successively in the mold and joined during the injection-molding process, made possible by using two different types of nylon for the valve's frame and flap. Once molded, the valve assemblies are then ultrasonically welded to the manifold, eliminating any assembly steps.

The intake manifold is made using the lost-core process while the plenum cover and the manifold are joined using vibration or shell welding. All of the secondary components are attached using self-tapping screws, which eliminates the need for threaded metal inserts. The active design incorporates six molded flap valves in the runners and a resonance valve in the plenum. Incoming air is ducted along a Y-shaped tube into two parallel plenums, one for each bank of cylinders. A resonance flap that separates or connects the plenums is located at the closed end. Individual runners branch off from the two plenums to the cylinder head. Each intake runner is connected to a third plenum via the performance flaps, which are actuated by a pushrod. When the flaps are opened, the runner lengths are reduced from 500 to 350 mm (20 to 14 in).

Mark IV announced at the SAE 2000 World Congress in March that its first thermoplastic manifold for North America is also being produced with DuPont's Zytel. It was developed by Ford and Mark IV with technical material support from DuPont. Ford will use the dual-plenum air-intake manifold for its 4.6-L SOHC Triton V8 engines on 2000 F-150/-250 trucks, as well as on some Expedition SUVs and Econoline vans. The manifold is an active system featuring a communications valve that allows the manifold to shift between its two plenums, which Mark IV says delivers optimum torque at a wider range of operating speeds.

Using Zytel enabled the company to add a new gasket carrier assembly, eliminating the compression limiters normally required on the gasket carrier assembly, cutting manufacturing steps, lowering piece count, and reducing the system complexity. The new component contains two injection-molded shells that are vibration welded, replacing the original component that was produced using the lost-core method. According to Mark IV, switching to vibration welding results in a smoother interior finish, reducing resistance to airflow, which in turn improves engine performance.

Rover worked with several companies for an all-plastic air-intake manifold module for its 2-L, four-cylinder turbodiesel engine. The module consists of an air-intake manifold, an engine cover, and an air-filter housing. All the components are injection molded using nylon resins from BASF Plastics. Ultramid A3HG7, a 35% glass-fiber-reinforced nylon 66, is used to mold the air-intake manifold. This material resists high engine temperatures and attack from hot oil, gasoline, and diesel fuel while maintaining high strength and stiffness.

The one-piece air-filter housing cover uses an internal rib structure to reduce noise emitted by the camshafts, the valve-drive assembly, and the fuel injectors, as well as noise produced by the vibrating column of air. It is molded by BASF of Ultramid B3GM24, a nylon 6 containing 10% glass-fiber filler and 20% mineral filler. The one-piece valve cover includes an oil-filler pipe, a base for the oil separator and pressure controller, and openings for the diesel-fuel injectors and the intake ports, which route a portion of the intake through the valve cover and the cylinder head into the cylinders. Reinforcing ribs acoustically optimize the valve cover, which is molded of Ultramid A3WGM53, a nylon 66 with 25% glass-fiber filler and 15% mineral filler.

The turbodiesel manifold module was produced using standard injection-molding techniques and vibration welding. It has a mass of 6 kg (13 lb) and was developed through an international joint venture by BMW, BASF Plastics, Robert Bosch Corp., Mark IV, Knecht, Joma, and IBS Brocke.

Featuring a thermoplastic rocker cover, Tritec's new 1.6-L, four-cylinder engine is an optional powertrain for the Dodge Neon in North America and the Rover R50 in Europe. Dana Corp. produces the cover from DuPont Minlon mineral-reinforced nylon to provide a series of integrated baffles to separate oil from the crankcase ventilation air supply. The rocker cover accommodates the PCV valve, includes a molded-in air make-up nipple, provides heat-staked inserts for mounting the ignition coil, and includes two heat-staked baffle plates. Functionality is improved within the engine through the use of an integrated oil pan gasket carrier made of DuPont Zytel nylon.

At the SAE 2000 World Congress, TI Group Automotive Systems exhibited what it calls the automotive industry's first electronically managed fuel storage and delivery system. The 2000x Smart Tank features its own in-tank computer that receives commands and delivers processed information directly to the vehicle's onboard computer network.

The tank itself is a plastic co-extruded, multi-layer design with a vapor barrier to control evaporative emissions. The complete system has only two connectors: one for the filler tube, the other for a subsystem assembly that includes a smart pump, a smart purge, electronic control module, and fuel-level diagnostic sensors that meet OBD II specifications. The tank incorporates internal fuel pressure generation and control, a stationary piezo sensor to measure fuel volume, vapor collection, carbon vapor storage, a fuel/fill stop valve, an all-position fuel reservoir, and a life-of-the-vehicle final filter. The plastic tank can be shaped to detailed vehicle specifications, with other advantages including higher efficiency and reduced electrical consumption.

TI Automotive also exhibited a corrugated hose product for fuel lines called Permblok. The hoses are made of plastic in single- or multi-layer construction for use in fuel vapor management systems. The new component allows easy part assembly and reduces the potential for kinking during installation and operation.

TI Automotive was formed in June 1999 following TI Group's acquisition of Walbro Corp. In September, the company expanded again by completing the acquisition of the remaining 51% of Marwal, a joint venture of Magneti-Marelli and Walbro. The company now claims that more than half of the world's annual car production relies on TI Group's fluid-carrying technologies.

If TI Group considers itself as having more than half of the world's fluid-carrying systems, Solvay and Plastic Omnium want what's left. The two firms have signed an agreement in principle to combine their automotive fuel systems operations in a new equally shared company. According to Solvay, the firm is the global leader of HDPE fuel storage and delivery systems, supplying more than 30% of all tanks currently in production in North America. Solvay was among the first to develop smooth-wall processing in the 1960s. That experience led to the development of lost-core injection molding in the early 1980s and the first production program of a glass-reinforced air-intake manifold.