Developments in automotive plastics

10 min read
Going ‘green’ is just one of the challenges facing today's car makers. (Picture © Olaru Radian-Alexandru. Used under license from
Going ‘green’ is just one of the challenges facing today's car makers. (Picture © Olaru Radian-Alexandru. Used under license from

Advances in materials, technology and applications for thermoplastic and thermoset engineering plastics and composites for the automotive industry were featured during the event in Detroit in April. Presenters gave summaries of successful plastic usage and proposed new applications for plastics, their fillers, formulations, and manufacturing techniques.

Steven Magryta, Powertrain Materials Engineering, General Motors, focused on the current use of plastic components in gasoline engines and diesel engines, as well as transmissions. He concluded by suggesting potential opportunities for plastics in powertrain applications.

George Kowalski, Ford Motor Company, outlined his company's coolant system component strategy. Traditionally metal has been used for coolant system components because of their high temperature resistance, chemical resistance, and dimensional stability. These requirements virtually eliminated plastics as the material of choice for these applications. However, with the new plastics, additives and composites becoming available, plastics for these applications are being revisited.

Josh McIlvaine, Technical Development Specialist, DuPont Automotive, believes that the drive for mass and cost reduction keeps designers and engineers looking to thermoplastics, especially for structural applications. Additionally many companies are committed to carbon dioxide (CO2) reduction. Many of the obvious substitutions from metal to thermoplastic in vehicles have already been made. Now is the time to find the hidden areas for these switches and he indicated he had a process to quantify the various options.

Dr Suresh Shah, Delphi Corporation, explained the various materials and process developments in underhood applications for vehicles. Included in his survey were heating, ventilation and air conditioning (HVAC) components, radiator components, fan-shroud assemblies, air intake manifolds, engine covers, rocker panel covers, and others.

New applications for polymers

As with any AutoEPCON conference, much of the focus was on new plastics, or new applications for existing plastics. These involved a wide range of suggested applications, from gears to backlighting, to windows (glazing), to a myriad of underhood applications.

Dr Jonathan Ross Sergeant, Exatec, spoke on the new developments of polycarbonate (PC) automotive glazing and was prepared to ‘bust some myths.’ Exatec and SABIC teamed up to present ways to make polycarbonate the material of choice for automotive panoramic roof systems, highly integrated backlites and innovative door modules. Exatec has patents that describe various glazing applications, including multilayer systems that include ultraviolet (UV) absorbers and abrasion-resistant materials. The advantages of plastic windows include design and shape flexibility, weight savings for both fuel economy and lower centre of gravity (especially with sun roofs making for added safety in roll-over accidents), and reduced complexity by allowing moulded-in features.

Michael Fye, Delphi Electronics & Safety, discussed details of the construction and development of the award-winning Color Converting Plastics for Electronic Display Applications (SPE's Automotive Division 2007 Grand Prize winner). This invention began with a desire to move away from the use of heat-generating incandescent lights for backlight automotive electronic display applications. The light from these incandescent bulbs was directed and filtered to create the distinctive colours of the backlighting desired by the various niche markets. The incandescent lights were not highly durable, gave off a lot of heat, and were expensive compared to the newer technology – light-emitting diodes (LEDs). But the LEDs (especially the early LEDs) were not as bright as incandescent bulbs and they had limited colour choices. While LEDs improved over the years, they still exhibited overall effects inferior to those produced by the incandescent bulbs.

Joining forces to solve this problem were Delphi Electronics & Safety staff and compounder RTP Company. They reasoned that, as an alternative to the filtering of the light from incandescent bulbs or white LEDs, why not make a series of fluorescent and light scattering colorants for transparent polycarbonate? This resulted in a process whereby the fluorescent colorants are excited by the light from the standard LEDs and fluoresce a different colour light. Once the backlights were ready, the packaging engineers wanted to reduce the individual number of LEDs by using the newer brighter LEDs and a system to direct the light to the backlighting location. This direction system, called light distribution pipes or light tubes, was created in the 1980s for incandescent bulbs. However, adapting the system to use newer LEDs required redesigning the circuit boards to allow the light to be routed through the boards rather than around them, in order to minimise the path of the light tubes. This was accomplished with some difficulty and some protests from the circuit board engineers. In the end, all of these changes resulted in a very flexible backlighting system capable of supplying uniform, inexpensive, relatively cool, backlighting tailored for niche-colour applications.

New or improved polymers

Dr Joseph V. Kurian, DuPont Automotive, reported on some of the company's renewable resource-based products. He discussed several new families of plastics based on DuPont's new method of producing propanediol (PDO) (also loosely known as propylene glycol), which they call Bio-PDO™. The Bio-PDO is derived from corn sugar using a patented and proprietary fermentation process and the Bio-PDO can be used as a replacement for petrochemical based 1,3-propanediol and/or 1,4-butanediol (BDO) in the production of plastics and elastomers. The advantages of Bio-PDO are threefold:

  • the product is renewable;
  • it has superior properties over the petroleum-based product it is replacing; and
  • there is an estimated energy saving of 40% over petroleum-based propanediol.

With the polymerisation of Bio-PDO with either petroleum-derived terephthalic acid (TPA) or dimethyl terephthalate (DMT) DuPont forms polytrimethylene terephthalate (PTT or 3GT™). PTT contains 37% renewable material and has performance properties (chemical, electrical, mechanical) similar to those of polybutylene terephthalate (PBT), with improved surface appearance and gloss.

Another product DuPont will produce from the Bio-PDO is a high-performance thermoplastic elastomer with property and performance improvements in temperature range and elastic recovery comparable to petrochemical-based products.

Dr Mike Zimmerman and Chris Lee of Quantum Leap Packaging reported recent developments on a thermoplastic liquid crystal polymer molecule and its compound formulations, leading to a new material with isotropic properties which may replace metal in applications where other more conventional plastic formulations have so far failed. Their product has material properties that include stability at temperatures to 420°C, moisture permeability similar to glass, coefficient of thermal expansion (CTE) similar to metals, very low shrinkage, and excellent adhesion to metal.

Bruce Mulholland, Ticona Engineering Polymers, presented some advances in the UV light stabilisation of copolyester elastomers (COPE). There are many high performance elastomers on the market but the problem of UV-induced oxidation prevents the broad use of these compounds. Ticona has developed a new series of elastomers that can maintain 100% of its ductility after 2000 kJ/m2 exposure, 200% of the required industry standard. It exhibits no colour change, no blooming, good thermal stability, and resistance to UV and hydrolysis. The secret to the UV resistance is the proper combination of the additive package of UV absorbers, antioxidants and hindered amine light stabilisers (HALS). The UV absorbers are location and wave length sensitive; the antioxidants are used up with time and require some but limited mobility whereas the HALS is self renewable but must be well placed and distributed. Ticona suggests they have developed that correct blend and now their product Riteflex® TPC-EP can be used for injection moulded applications for interior automotive such as soft-touch knobs, trim, emblems, and monofilament for automotive seating fabric.

Douglas Bosch, DSM Engineering Plastics, spoke on the usage of the Arnitel® family of thermoplastic elastomers (TPE) in automotive underhood applications. It combines the strength and processing characteristics of engineering plastics and the performance of thermoset elastomers, thereby providing benefits in processing and productivity. Arnitel C shows good potential to reduce the weight and mass of wiring and cable through ultra-thin wall coatings.

Dr Jeremy Klug of Ticona presented information on behalf of Vinícius Fernando Mardegan, Product Marketing Manager – POM, on an improved class of long glass fibre polyacetal (POM) thermoplastics. The uniform distribution of the glass fibre and the excellent bond between the glass and the polymer greatly improves the properties of this new product. The POM exhibits good stiffness while providing a new and unique level of impact resistance. With this impact resistance and built-in lubricity the presenter suggests a potential for breakthrough applications including automotive sunroofs, seating systems and windshield wipers. It also exhibits excellent chemical resistance, particularly around fuels, which will open up more applications for fuel system components. The author suggests it can replace polypropylene (PP), polyamide (PA), polyester composites, and metal in certain applications.

Dr William E. Sattich of Chevron Phillips Chemical Company has been working on the stability of polyphenylene sulphide (PPS) compounds and alloys in long-life engine coolants. PPS is very resistant to chemical attack and the company claims that below 200°C no organic solvent will dissolve PPS and only the strongest acids can attack it. It is very resistant to bases and salts. Because the PPS does not degrade the bond between the fibre or fill material and PPS will not change and the strength of the PPS is maintained. Sattich produced a series of test results on five PPS formulations varying from 40-65% fibre and/or fill material. He tested tensile, swell and impact during exposure to thousands of hours in a variety of antifreeze formulations. The PPS held up very well, better than the one sample of PPA used for comparison.

Peter Schmieg and Michael Pilarski of DSM Engineering Plastics worked on a new high temperature PA 46 family. They discussed one version, Stanyl Diablo®, which has exhibited good properties for over 5000 hours at 210°C. They suggest replacing metal parts such as turbo diesel system components where thermoplastics have not been technically viable. The presentation showed pictures of various engineering plastics aged at 210°C. PA 66 and polyphthalamide (PPA) exhibit a slowly growing char layer which decreases the cross section and strength of the part. The new PA 46 formulation shows little char and maintains its properties. The charts indicate that while earlier PA 46, PA 66 and PPA lose much of their physical properties by 2000 hours at 210°C, after an initial small loss in properties Stanyl Diablo properties are constant between 2000 and 7000 hours. Weld strength after aging at temperature is also very good. A second possible use for this new material is lighting applications, e.g. light sockets. With its high temperature stability it exhibits ultra-low out gassing.

A second paper covering properties of PA 46 was presented by Steve Wasson, Business Development Manager at DSM Engineering Plastics, who focused on the low wear and high fatigue capabilities of PA 46 for gears in automotive uses. The presentation begins by stating the challenges of various countries' new fuel economy and emission standards requiring higher fuel mileage and lower emissions for diesel engines. These will drive innovation in the underhood applications for these engines. Of importance are reliable gear sets which will be durable well past 10 million cycles and operate at temperatures over 130°C.

The presenter suggests that PA 46 is ideally suited because of its uniform structure which promotes crystallinity (70% vs. 40-50% for PA 66 or acetal). The paper reviewed numerous tests exhibiting the strength and durability of PA 46 vs. a wide range of other engineering plastics. Especially impressive was the impact resistance of PA 46, which tested better than the 11 other widely-used polymers.

Two presentations dealt with acrylics in various automotive applications. H. Reid Banyay of Arkema suggests that moulding in colour PMMA shows good weatherability after five years when used for automotive trim while other technologies that use coatings exhibited some changes in surface chemistry and appearance after that time period. A second presentation on advances in acrylic-based materials designed for use in automotive trim was delivered by Peter D. Colburn, Technical Manager, CYRO Industries/Evonik-Degussa Corporation. Colburn suggested that the long history of acrylic use in automotive lighting is now being extended to trim applications.

Process improvements

Tim Hoel of DQR Company described his company's use of acoustic imaging for failure analysis. In order to characterise a polymer's usefulness in design, DQR uses an acoustic microscopy scanning imaging method. Voids are now able to be analysed with correlation to material density or porosity measurements. Acoustic pulse echoes employing the velocity of sound are used to measure part thickness. He also presented a ‘point and click’ method of obtaining measurements and artifact counts from any digital image. To prove his methodology, a case study was presented to qualify a cross-linked urethane elastomer and its comparison to a control.

Several papers dealt with improvements in the manufacturing process. Mike Greer of Chevron Phillips Chemical presented information on the importance of mould temperature in the manufacturing of products from PPS. PPS exhibits excellent chemical resistance, dimensional stability and high temperature resistance but this presenter points out that it is very important that these properties not be compromised by improper mould temperatures. The presentation outlines some analytical methods to determine if the proper mould temperatures were used and how variations in the mould temperature affect the critical properties, including surface finish.

Julien Mourou of General Motors presented information on surface contoured cooling, also known as conformal cooling, of injection moulding equipment. By improving the cooling cycle it is possible to reduce cycle time and reduce warpage.

Jim Greene and Chris Korson of LPKF Laser and Electronics presented information on hybrid welding processes using laser and halogen lamps. The speaker outlined two methods of joining plastic parts by laser welding. For this application the parts must be of two different materials, one which can transmit laser light and one that absorbs and is heated to the melting point by the laser light. Fillers, colours and thickness of the materials affect the ability of a material to absorb or to transmit laser light so the composition is of great importance for the choice of this welding method. The laser welds can be very precise resulting in a product with no leaks, on line process control, no mechanical stress on the part, flexibility in location of the welds, and reduced cost. A second way to use this technology is a hybrid weld in which the welded surface is heated by halogen radiation and the weld is again accomplished with the laser. This reduces stress on the weld itself resulting in higher weld seam strength, no residual stress, as well as a larger process window, and faster process speed.

Predictive modelling

Richard Baxendell, Bayer Material Science, and Gregory L. Schlegel, Shertrack LLC, whose companies teamed up to generate a model and simulation to quantify and qualify manufacturing improvements, co-presented their findings. Of special interest was reduction of the dead and slow moving inventory and improving customer satisfaction. They also wanted to test the various tools used in the production plant, such as Six Sigma, to see how effective they were. The team proceeded to write a model to test their manufacturing process. Called SNAPPS™ Digital Model it factored in customer demand, scheduling and production output of the compounding facility.

Once the model was written and proven, then using a Design of Experiments it was possible to test the effects of many factors, including the lead time required for orders. The modelling and initial production results indicated that a large improvement in customer satisfaction and a considerable reduction in inventory were possible while still maintaining high plant utilisation. It appeared that reducing the made to forecast parts would help greatly in this effort. Bayer concluded that very compelling improvements are possible using this technique, especially in complex operations, but they pointed out that the improvements require new work processes and new tools to achieve these goals.

Going green

Mary Fraser, BASF Engineering Plastics, opined what should be core to a successful company's business philosophy – sustainable development. Many items need to be considered when a company is committed to ‘going green.’ It is more than just producing a green product; it is all about optimising economic success, while protecting the environment and being socially responsible. The speaker believes this requires a measurement technique so that the company can judge the effects of its decisions.

BASF's Eco-efficiency Analysis includes a workshop where attendees will learn the tools by which to compare and compromise in order to compile a business strategy and product design and development that will take into account the relationship between economical and ecological advantages and disadvantages from among the company's various options. The entire life cycle of the product, beginning with its raw material selection through to its end of life disposal or recycling, is taken into account and an ‘ecological footprint’ is generated based on materials consumption, energy consumption, emissions to air, soil, and water, risk potential, and toxicity potential.