At the September 2021 VDI Plastics in Automotive Engineering Congress, Martina Hetterich, project manager for advanced development, and Matthias Michl, head of team automotive application development at Waldkraiburg, Germany-based Kraiburg TPE, presented the company's work.
The resins are filled with 3M Deutschland GmbH hollow borosilicate glass spheres, iM16K and iM30K bubbles.
They pointed to low 0.7-0.9 grams per cubic centimeter density, due to 0.13 to 0.60 grams per cubic centimeter spheres, enabling the material to weigh up to 25 percent less than the next lightest TPE material (thermoplastic vulcanizate) and 50 percent less than PVC, with much lower compression set than conventional TPEs and TPVs used for automotive applications, the same level as EPDM rubber.
Out of 3.59 kilograms of potential automotive exterior application weight savings, up to 40 percent of the weight can be reduced in glass run channels and door seals, they said.
Within 1.62 kg of 30 percent interior weight saving is possible in the interior, with 1.2 kg saved from floormats alone.
In the powertrain, the spheres can save 30 percent vs. conventional TPEs in active grill shutters, grommets and battery systems and can save 40 percent in EPDM engine cover seal substitution.
There are also efficiency and environmental benefits over conventional TPE, according to the company. With low heat capacity enables faster cooling time, cutting molding cycle time and saving energy. Higher packing density than with conventional mineral fillers enables higher filler content, reducing TPE polymer content and providing low shrinkage and warping.
Although the presentation focused on lightweight TPE automotive applications, Lossburg, Germany-based injection molding machinery producer Arburg GmbH + Co KG demonstrated molding of hollow glass sphere filled TPE stackable tote boxes weighing 675 grams at its 2018 technology days open house, using a compound from Viersen, Germany-based Hoffmann + Voss GmbH, which uses spheres in both virgin and recycled compounds. A doorstopper molded by Arburg weighs 63 grams in general purpose TPE, 44 grams in lightweight TPE and was molded in 29 seconds, compared with 49 seconds in conventional TPE.
With its "homogenous" surface and good adhesion to nylon, polypropylene and PP/nylon blends, the material is suited for use in traditional multicomponent injection moldings for power tools, sport and leisure applications. It should have appeal in aerospace applications, including drones, according to Kraiburg.