While other strategies such as engine technologies (smaller engines, diesel engines and utilising turbochargers), start-stop, and economy mode (50% of cylinders operating) admittedly have a greater effect on improving fuel economy than lightweighting, there’s no doubting that utilising plastics to eliminate vehicle mass remains an important initiative at automakers.
And that’s not to forget the fact that plastics also play an important role in the abovementioned drivetrain-related developments. Opportunities also abound for plastics in electric and hybrid electric vehicles.
Notes Paul Hardy, Product Manager, Performance Materials at A. Schulman: “For every 10% weight reduction there is about a 5–7% fuel economy improvement, therefore for every 300 lb. removed from a car, you pick up about 1.6 mpg.” This itself will not enable automakers to meet the CAFE mandate of improving fuel economy from 36.6 mpg in 2017 to 54.5 mpg in 2025. “Regardless,” notes Hardy, “driving weight out of parts plays an important role in a small way to meeting the mandated fuel economy.”
Hardy will be discussing lightweighting through plastics in detail at the inaugural automotive conference— Lightweighting Strategy & Drivetrain Efficiency for All Supplier Tiers & OEMs— to be held in conjunction with Advanced Design & Manufacturing (ADM) Cleveland on March 29 and 30 at the Huntington Convention Centre in Cleveland, OH.
Metal is the primary culprit when it comes the weight of a car and, while suppliers of these materials are endeavouring to do their bit through developing high-strength steels and alternative materials such as aluminium and magnesium alloys, plastics have succeeded in displacing metal parts, particularly with glass-filled polyamide (PA), notes Hardy.
“Once automakers are comfortable with deploying plastics in [structural] frames and to replace metal supports, then the real weight savings will come,” he adds. One example is replacement of metal supports for the bumper. Other areas where plastics are making inroads include water pumps, where polyphenylene sulphide (PPS) is the material of choice.
The coming of age for structural applications
Structural applications may come into their own with carbon fibre becoming more economical notes Hardy. A. Schulman offers a high-modulus grade of polyamide with a 40% carbon fibre loading, for example. This and glass-fibre-reinforced grades typically employ blends of PA 6 and other types of polyamide to achieve a balance of heat resistance and low density.
To further reduce density, A. Schulman has also developed PA/PP (polypropylene) blends with a similar heat resistance versus density trade off. Targeted applications include fan shrouds, air shutters and other non-structural components. The nylon-rich PA/PP alloys promise 8 to 11% weight savings.
“PA/PP alloys have many benefits to the moulder, [including] reduced moisture pick up, reduced drying times, lower injection moulding temperatures and improved dimensional stability,” notes Hardy. Cost savings are also achievable. Hardy cites an example of production of 200,000 parts that cost $437,393 overall with its Schulamid 6GF30TC PA/PP alloy grade versus $476,194 for a 30% glass-filled PA grade.
Hardy will discuss more cases studies during his presentation at ADM Cleveland’s Automotive Conference, including the use of nanofillers, and replacing PA with PP, as well as development of highly filled high-flow PP grades.