Polypropylene proved too strong for steel when industrial cleaning equipment manufacturer Kärcher was specifying materials for the chassis on its new mid-class and high-end range of hot water high-pressure cleaners. The new chassis represents Kärcher’s first use of plastics in the application, which traditionally has been produced using steel. According to its supplier, LyondellBasell Industries, the PP chosen, Moplen EP240T, offers a better melt-flow rate, impact strength and chemical resistance compared to standard PP grades.
As a load-bearing element for the cleaner, the chassis contains more than 300 pieces; the part is 1254 mm long, 747 mm wide, 495 mm high, and weighs 22 kg. “Our new model required a material that permitted more design freedom and production flexibility than steel,” said Bernd Gaßmann, process coordinator at Kärcher. He said switching to PP enabled the OEM to eliminate several manufacturing steps, and the processability of the material enabled Kärcher to include parts such as the air duct and the holding tanks for water and detergents directly into the chassis instead of assembling these in secondary steps. The PP chosen is being used to produce six models in the series, with the chassis infrared welded.
Standard PP grades with a comparable balance of stiffness and impact resistance have a melt flow rate (MFR) of up to 25 g/10min, says the supplier, whereas Moplen EP240T has an MFR of 48 g/10min. “Flowability on the one hand, with stiffness and impact resistance on the other hand are diametrically opposing forces. However, the Moplen resin offers an ideal balance of both,” said Daniel Schneider, application development and technical service manager for injection molding at LyondellBasell. “Kärcher also required high chemical resistance, and PP can address this specific need of applications for exterior use.” —[email protected]