DuPont plastics make sense in automotive sensors
Increases in electronic sensors in the modern car have created new demands for electrically-friendly plastics to protect these vital yet delicate electronic devices. DuPont™ Zytel® polyamide and Crastin® polyester resin spearhead DuPont’s expanding portfolio of plastics for automotive sensors, now used in an increasing number of commercial sensor programs.
In the recent evolution of the automobile, the stand out change is arguably the dynamic growth of in-car electronics. The digital automobile has arrived, bringing with it a multiplicity of electronic control units (ECUs) aimed at reducing fuel consumption and engine emissions, improving safety, increasing driving assistance, and enhancing comfort, in response to legislation and customer expectations.
Park a 1988 Audi 200 V8 next to a 2012 Audi A8, for example, and the external changes are far less dramatic than the proliferation of internal electronic functions. While the 1988 model had only a few non-networked electronic systems and functions activated via relays, the latest model contains complex network architecture with a central gateway, over 100 ECUs, and seven bus systems—communication channels that integrate individual control channels.
All major automotive OEMs produce passenger car models with similarly complex electronic systems, applied throughout the vehicle to powertrain, chassis, body and interior.
Sensors—the vital link
However, to deliver the benefits of electrification to drivers, passengers and manufacturers, these electronic management systems require sensors to monitor and input data from virtually every vehicle function. Sensors are the vital link, communicating information to the ECU such as drivetrain operation, ride and handling, brake wear, tire pressure, wheel speed, external road conditions and internal climate. Control of the latest 6- to 7-speed automatic transmissions, for example, is highly regulated by transmission input sensors, transmission output speed sensors and torque sensors.
Sensors make a critical contribution to safety in most of these systems. In stability management/ride control systems, for example, data from sensors is monitored and active suspensions are adjusted automatically to improve ride handling and comfort, and, most importantly, to reduce roll-over risk.
Along with the big increase in the number of sensors in the modern car have come new demands for sophisticated, electrically friendly (EF) plastics to encapsulate and protect these delicate units.
The sensitivity of ECU electronics requires specialty materials to meet challenging performance and durability requirements. Material specification is critical, and many standard polymers and formulations are no longer adequate for these high value and highly engineered components.
Selecting the best fit by achieving the closest match between the application and the material can mean the difference between passing a durability test, and starting from scratch. Durability requirements are changing rapidly, so it is important to reassess the material and its suitability for new programs. A plastic resin that worked well on a coil sensor in production 10 years ago may be unsuitable for the next generation integrated circuit (IC) sensor.
Expanding portfolio for better sensors
DuPont is responding to these changing expectations with an expanding portfolio of EF products developed specifically to meet customer needs in ECUs for engine management, safety and comfort. They offer enhanced corrosion protection, durability and reliability for sensor electronics, and are laser markable. In processing, these special polymers are generally high flow to enable optimum filling of complex design molds with thin wall sections.
This article reviews the key high performance DuPont products for ECU sensors and actuators—DuPont™ Zytel® polyamide, DuPont™ Crastin® polyester resin.
Specialized grades of DuPont™ Zytel® high performance polyamides spearhead the company’s portfolio of products for automotive sensors and actuators. They are particularly suitable for challenging underhood applications and offer:
- Long-term resistance to heat and cyclic temperature stress
- Resistance to engine and transmission oils, fuels, glycols, water and steam
- Exceptional dimensional stability to reduce thermo-mechanical stress on encapsulated electronic components
- “Wire friendly” characteristics to enable corrosion-free contact with metal inserts and lower-pressure encapsulation
- Fluid-tight encapsulation of electronic components
- Resistance to hydrolysis for better signal detection accuracy
- Outstanding flow behavior to enable miniaturization, overmolding and thin-wall moldings
- Suitability for challenging new applications in Diesel Emission Fluid (DEF) / AdBlue® systems
Best for sensors
The broad portfolio of Zytel® PA and Zytel® HTN high performance polyamides are produced by DuPont, the largest, most globally networked nylon manufacturer exclusively focused on the resins market. Grades most frequently specified for sensors and actuators, branded “EF” (electrically-friendly) include:
- Zytel® PA 6/6 — extraordinary overall general-purpose resin offering an excellent balance of mechanical and molding properties
- Zytel® PA 6/12 — an extremely low viscosity "soft fill" polymer for minimal strain on overmolded wires and components. This grade offers low moisture absorption and better salt and chloride resistance, and is specified for aggressive under car applications such as ABS sensors
- Zytel® HTN — for highest chemical resistance in aggressive environments offering lower moisture absorption and higher strength and stiffness than PA 6/6
- Zytel® reinforced grades — Zytel® is available in reinforced nylon 6/6, PA 6/12, PPA, and toughened PPA grades, and also with multiple glass loadings. In addition, with the growth in laser welding, Zytel® grades have been developed in natural colored resins to suit this efficient design process
Crastin® polyester resin
Crastin® PBT thermoplastic polyester resins, based on polybutylene terephthalate, are currently available in over 100 different grades suited to an enormous range of industrial applications. Grades specified for sensors and actuators include:
- Crastin® PBT HR — offering mechanical stiffness and toughness, good friction and wear resistance, excellent electrical insulation, high resistance to hydrolysis, heat and cyclic temperature stress, and enhanced flowability and weld line strength.
Millions of sensors rely on DuPont plastics
DuPont™ Zytel®, Crastin® and Vespel® parts are increasingly specified by OEMs looking for the best materials to protect and enhance the operation of sensors and actuators in automotive ECUs.
Following are examples of many commercial applications for these products:
- Engine speed sensor by Siemens uses Zytel® HTN
Zytel® HTN was chosen for overmolding onto an engine speed sensor by Siemens VDO Automotive AG because of its high temperature cycling resistance, low CTLE characteristics, good flow and overmolding tightness.
- EGR solenoid valve by Valeo uses Zytel® HTN
Valeo S.A. specified Zytel® HTN for an exhaust gas recirculation (EGR) solenoid valve to ensure resistance to high temperature cycling, water at 120°C, low CTLE characteristics, good flow and tightness in overmolding.
- Tire pressure monitoring system by SmarTire uses Zytel® HTN
SmarTire Systems Inc., uses the high performance characteristics of Zytel® HTN PPA resins for a lightweight and durable casing for its externally mounted Tire Pressure Monitoring System for commercial trucks. The Zytel® resins were chosen because they offer the rigidity, durability plus heat and impact resistance required to meet heavy tire spin loads, intense pressure levels that can reach 200 PSI, and heat in the brake assembly area as high as 200°C.
- UFS acceleration sensor by Bosch uses Crastin®
Robert Bosch GmbH selected Crastin® PBT HR for the protective body of an upfront acceleration (UFS) sensor because of its high resistance to hydrolysis, improved resistance to cyclic temperature stress, and high weld line strength.
Working with DuPont
DuPont offers more than 100 materials and product families for the global automotive industry. Through its global network of Automotive Development and Innovation Centers DuPont collaborates with customers to develop new innovations, materials, components and systems that respond to consumer desire for greater efficiency and for even better driving experiences. Contacting DuPont is easy via www.automotive.dupont.com. To learn more about DuPont’s Innovation centers visit www.innovationcenter.dupont.com/.