Plastic extrusions and injection moldings replace all-aluminum construction.
AeroCat B.V., www.aerocat.nl/
Airlines have long been removing nonessential weight from their airplanes to save on fuel expenses or add paying passengers. So it may be surprising that the trolleys carrying drinks, meals, and packets of pretzels or peanuts are made the same way they have been for years — out of aluminum.
AeroCat B.V., Tilburg, the Netherlands, a company that builds these trolleys, designed a totally new catering trolley made almost entirely of injection-molded and extruded plastic. The company partnered with Solvay Advanced Polymers, Alpharetta, Ga., plastics processor Bemis Manufacturing Co., Sheboygan Falls, Wis., and RFID expert Zetes Industries, Brussels.
The result, the Tigris trolley, a 4-ft-long × 14-in.-wide rolling cart, weighs 37 lb. A half-size, 22-lb trolley is also available. In comparison, most current trolleys weigh about 46 lb.
All 11 injection-molded parts and three extruded parts on the trolley are made from Solvay’s Radel R polyphenylsulfone (PPSU). Injection-molded parts, including two 3-ft × 10-in. panels that serve as the front and rear doors, use the R-7535 grade of PPSU which has a melt flow of 1.8 gm/ sec at 716°F.
The extruded parts are novel for their length and thin walls, according to Bemis director of market and business development Steve Kolste. “The challenge was extruding such a large profile with a thin wall and still providing the necessary strength and low weight,” he explains.
Using standard extrusion equipment but specially designed dies, Bemis extruded 39-in.-high C-shaped parts for the trolley’s body. Radel R-7700 PPSU’s consistent melt flow let the material flow evenly through the large dies. The 0.5-in.-thick structures are believed to be the largest thinwall PPSU extrusions, according to Kolste.
The hollow, multilayer, ribbed structures join to each other using a proprietary fastener-free technology for further weight reduction.
The two PPSU grades meet FAA flame, smoke, and toxicity requirements and resist aggressive cleaning agents. Radel R-7535 withstands notched-Izod impacts up to 3.0 ft-lb/in., while Radel R-7700 fractures at 10 ft-lb/in. The polymers also accept molded-in color and are said to insulate better than aluminum.
The trolley is designed for closed-loop recycling after an estimated 10-yr service life. This means retired or damaged parts will be shredded and reformed into new trolley parts. According to tests carried out by Bemis engineers, parts made from 100%-recycled PPSU perform the same as those fabricated from virgin PPSU or a mixture of recycled and virgin resins. In comparison, aluminum trolleys traditionally last about seven years, after which parts from three scrap trolleys can be used to make one reconditioned trolley with an additional five years of service life.
The plastic trolley’s long life and recyclability means the product’s carbon footprint is a factor of 2.2 less than that of an aluminum trolley, according to researchers at the Netherlands Organization for Applied Scientific Research (TNO). The estimate is based solely on the energy it takes to produce each type of trolley, divided by the trolley’s lifetime, and the energy savings achieved by recycling PPSU or aluminum instead of using virgin materials.
The lighter design saves on jet fuel, and PPSU’s insulating properties let catering companies use less dry ice to keep drinks cold. TNO estimates these factors could amount to a 310,000-ton CO2 reduction per year if 10% of the trolleys in service are replaced by the Tigris design. That reduction is equivalent to the CO2 emitted to provide the electricity for lighting 1.7 million homes.
It’s estimated the trolleys will need less maintenance than their aluminum counterparts. According to AeroCat commercial director Willem ten Barge, these benefits translate to a 100% return on investment in the first year in addition to lower airline-operation costs. Designers also hope that the trolleys will be more aesthetically pleasing.
The new trolleys are undergoing industry trials, and it is hoped they will earn European Aviation Safety Administration certification under a European Technical Standard Order. Once the design is approved, AeroCat plans to sell or lease trolleys to airlines as part of a total catering concept.