According to the European Environment Agency, the average European produces nearly five tonnes of waste per year. Only 38% of this waste is recycled, with much of the remainder ending up in landfill.

“As Europe looks to meet its environmental goals and create a circular economy, we must find new ways to recycle more materials,” said Janusz Sikora, a researcher at the Lublin University of Technology in Poland. 

Innovative technology developed by Sikora and his team on the NEWEX project makes it easier for manufacturers to create new products from waste plastic, saving time and energy, and producing better-quality materials. Researchers are now testing how efficiently this new technology can use multiple types of plastics and fillers.

Aggregate issues

Sikora’s objective was to improve our ability to extract high-quality resources from waste. “An example of this is the use of plastics made from recycled food, plant and shell waste,” added Sikora. “While this process is great for the circular economy, the properties of such plastics are significantly altered and have some limitations.” 

Sikora’s team focused on extruders, which are used to produce plastic-based products such as pipes, gutters and siding. These small, moulding-based machines melt granules of plastic before pushing the softened mass through a pre-shaped die, to create continuous objects with a specific profile.

“Typically, when it’s time to produce a new product, the operator only needs to exchange the extruder’s die and adjust the processing line,” explained Sikora. Unfortunately, when recycled waste plastic is used as the base material, things get a bit more complicated. 

“It all comes down to the grooved zone, which can be found in any quality extruder,” said Sikora. “This zone, located at the beginning of the extrusion process, exerts pressure on the plastic being fed into the machine and, by doing so, increases overall efficiency.” 

Getting into the groove

The key challenge facing manufacturers is that the extruders need a consistent plastic aggregate made up of one type of granulate. 

Not only is plastic made from recycled waste re-granulate, meaning it consists of many different granule sizes, each recycler produces re-granulate with different dimensions. Because this type of plastic loses its original properties, it is less suitable for processing. 

“Then there is the contamination that remains in the plastic, which makes it more difficult for the machine to extrude,” said Sikora. 

Not only do all these factors offset many of the environmental benefits of using plastics made from recycled waste in the first place, they also make using such material less cost-effective, and therefore less appealing to manufacturers.

“From conversations I’ve had with entrepreneurs, I learnt that what they want is an extruder where they can change the geometric features of the grooved zones.” 

In other words, what is needed is a solution that allows one to adjust the dimensions of the grooves according to the dimensions of the plastic’s granulate or re-granulate. 

Smooth operator

Inspired by these conversations, Sikora unveiled the EU-funded NEWEX project. “Our goal was to adapt a single screw extruder so it could process plastics made from recycled waste as efficiently as possible.” 

Bringing together an international team of specialists, the project developed virtual, digital and 3D models of the geometric elements of the grooved zone and of the rotating barrel segment. Next, the research team conducted computer simulations, animations and calculations.

This work ultimately resulted in the development of a prototype extruder that allows users to continuously change the design elements of the grooved feed section by independently changing the depth of each groove and the number of grooves. It also features a modified barrel that can rotate in either direction of the screw and at the desired speed, while the extruder screw has been modified to adapt to the modified barrel.

“The NEWEX design features a number of moving elements that, under the influence of increased temperatures, undergo thermal expansion,” said Sikora. “This causes the liquid material to flow into the gaps between the moving elements.” The NEWEX solution is geared towards extruders with an output range of several tonnes of plastic per hour. 

Industry 4.0

Although the prototype was originally meant to be used as a demonstration tool located at Lublin, it soon attracted the interest of a Polish extruder company. Together with some of the partners from the NEWEX project, and with the support of the EU-funded PROMATAI project, they are now working to further advance the extruder prototype, integrating artificial intelligence functions into the process that will allow the extruder to automatically adapt the grooved zone to match the size of the feed material.

“This is good news for small manufacturers and even better news for the environment,” said Sikora. 

The NEWEX project was undertaken with the support of the Marie Skłodowska-Curie Actions programme.