Recycled plastic dishwasher component proves a big point

Dishwasher case bottom. Photo Credit: Fraunhofer Institute for Structural Durability and System Reliability LBF

We all want to use more recycled plastic, but here’s the problem: Every time plastic is recycled, the polymer chain grows shorter, so its quality decreases; and who wants to buy something of lower quality?

Which is why it might be a big deal that researchers at the Fraunhofer Institute for Structural Durability and System Reliability LBF in Darmstadt, Germany, working together with partner companies Bosch GmbH and Bosch-Siemens-Hausgeräte GmbH, have demonstrated that recycled plastic can perform similarly to virgin plastic if the recyclate is processed efficiently. And they use dishwasher case bottoms to prove it.

First, Bosch optimized recyclate from the housing of automotive starter batteries by mixing in additives to increase the strength and enhance the visual properties. Next, the LBF team had to demonstrate that the optimized material could be suitable in a demanding application…and they chose dishwasher case bottoms, which form the base structure of a dishwasher, holding the side walls and housing ancillary components such as the pump, status sensors, and salt reservoir.

The researchers produced test specimens and subjected them to a set force around 100,000 times in an automated process – the number of times an average dishwasher door will be opened throughout a service lifespan of around 18 years. The tests showed that the recyclate had similar stiffness properties to that of virgin plastic. “More importantly, however, both materials behave exactly the same way in terms of plastic deformability,” said LBF scientist and research team member Dominik Spancken.

And on tests performed on the finger-thick pin on the dishwasher case bottom – which is subject to mechanical stress every time the dishwasher door is opened and closed and is therefore subject to the greatest load on the dishwasher case bottom – the resilience values recorded for the pins made from recyclate differed only very slightly to those made from virgin material.

“In summary, it’s fair to say that the recyclate can handle the same stresses as virgin material,” Spancken said. “A dishwasher case bottom made from recyclate is indeed possible and swapping from virgin plastic to recyclate would make a significant contribution to a sustainable complete appliance.”

The end goal, he continued, is to convince more experts and companies to use more specially blended recyclate in other higher-end products.