Thermoplastics in Transit Interiors – Weighing the Advantages
Mass Transportation’s (mass transit buses, railcars and aerospace) design and manufacturing processes have been trending towards requirements for greater fuel efficiency, providing a luxury riding experience, and the need for enhanced safety. Using buses as an example, design teams and OEMs have replaced steel and aluminum components with thermoplastics and thermoplastic composite materials. Upgrading to thermoplastic components on average offers 55% weight savings and meets the static loading requirements of the American Public Transportation Association. Thermoplastics are growing in popularity, offering industry focused material options that are rigid, and durable, and a manufacturing process that enhances design capability, lead time, and look and feel.
Why Reduce Weight?
As more mass equals more fuel consumption, utilizing materials that reduce the overall weight of the passenger buses, railcars, and aircrafts leads to decreased energy consumption, less brake and tire wear, and lowered emissions. Cutting vehicle weight by 110 pounds reduces 5 g of carbon dioxide emissions per kilometer and increases fuel economy by two percent. (Source: “Vehicle Weight Reduction for Optimal Performance” – DuPont
Modern transportation vehicles are becoming lightweight and fuel-efficient because of the use of thermoplastics for many interior components. Door, wall, and ceiling panels, dashboard surrounds, window masks or shrouds, seatback shells, armrest shells, bulkhead components, luggage racks, and display housings are just a few of the interior components that can be manufactured with the heavy gauge thermoforming process. While the materials industry as a whole has focused on lightweight solutions, thermoplastics offer a complete answer through a combination of strength, rigidity, and low density. For example, thermoforming produces components that weigh 30% less than comparable components made from fiberglass and 250% less than aluminum components. Interior components made from thermoplastics may make up nearly half of the volume of an automobile. However, those same, now lightweight components, contribute less than 10 percent to the weight of the vehicle. (Source: “A Lighter Future with Thermoplastic Solutions”, Lightweighting World.)
Industry-Compliant Thermoplastics with Emphasis on the Environment
The benefits of thermoplastics go beyond light weighting. Interiors for aircraft, coach and city buses, trucks, and passenger rail cars require the use of FST (Flame Smoke and Toxicity) compliant materials. All coach and city buses in the United States must meet the U.S. Department of Transportation Docket 90 safety specification for flame spread and smoke emissions. Motor Vehicle Safety Standard 302 Fire Test requirements apply to interior trim parts used for trucks. One example of a material now commonly used for interior aircraft components and interior rail applications is amorphous polyetherimide (PEI-Ultem) which complies with FST standards while providing strength and aesthetic appeal. Along with meeting compliance standards, PEI thermoplastics also resist damage caused by exposure to halogenated hydrocarbons, alcohols, and aqueous solutions. In addition, PEI thermoplastics resist warpage when exposed to heat for long durations because of a heat distortion temperature (HDT) rating of 350o F (176o C).
The manufacturing process for fiberglass emits high levels of volatile organic compounds (VOCs). In contrast, the use of very long fiber-reinforced polypropylene (PP VLF) thermoplastic compounds reduces levels of VOCs to compliance with the open air and enclosed application specifications set by international legislation and automotive OEMs. In addition, the PP VLF thermoplastics meet or surpass standards for odor and fogging.
Parts manufactured from fiberglass cannot be recycled. However, parts made from PP VLF thermoplastics can be recycled, have a lower life-cycle energy footprint and a lower life-cycle greenhouse gas emission. Manufacturers of mass transportation components use PP VLF thermoplastics for instrument panels, overhead and center consoles, seating, and storage bins.
Aesthetic Appeal: On-Time and Within Budget
Thermoplastics can improve the aesthetic design features of interior components used for mass transportation vehicles at a fraction of the cost required to obtain the same level of complex designs with other manufacturing processes. Low or high gloss surface finishes, custom surface texturing, complex geometric part design, and coloration are all capable, cost feasible, and can be manufactured quickly with the thermoforming process.
In-mold design and decorating enables the manufacturing of these high-level design features, resulting in part construction with consistency, precision, and a negligible impact on part cycle time. While in-mold texturing and pre-textured plastic may require a slightly higher initial investment than a simple design, the process ensures consistent part-to-part aesthetic detailing and minimizes cost by eliminating additional labor or processing. As a result, in-mold design can produce complex designs and custom surface finishes with a minimal impact on cost and lead time.
The use of thermoplastics in component production also provides the option of producing plastics with coloration that resist stains, graffiti, and chemicals and that do not chip or vary in tone or color. Moreover, using integral colored plastic eliminates the added cost and lead time of post-production painting. Coloration allows manufacturers to achieve a desired color finish and precise color matching along with durability. You can also have thermoplastic components that have specialty finishes, such as wood grain or metallic patterns and overlays, capturing design intent.
Aesthetic appeal also is achieved through geometry and a seamless appearance. Manufacturers can take advantage of the thermoforming process to build complex geometric designs with precise part mating and give the appearance of nearly seamless multi-part assemblies. With complex designs being accounted for within the part’s tooling, the high level of quality has a minimal impact on cost or lead time.
Productive Plastics is a heavy gauge thermoforming custom components manufacturer, with vast experience with thermoplastic manufacturing for transportation applications. Contact us for more information.