Stemma: at the forefront of technology and sustainability

RE-YU technology is ready to establish itself as the most innovative and sustainable solution to recycle polyurethane waste, a key resource for innovating the footwear sector and safeguarding the environment.

In the vast and competitive landscape of the polyurethane industry, one company stands out for its innovation and technical expertise: Stemma Srl. Specializing in the production of polyurethane moulding technology and machines, Stemma has earned a solid reputation as an industry leader. Thanks to a team of technical experts who work in synergy with clients to create unique products, the company offers customized solutions for every need and anticipates market requirements.
Strongly committed to research and development, Stemma has long focused on sustainability and the development of new production processes to reduce environmental impact. Officially presented at the recent Simac trade fair in Milan, the RE-YU technology for recycling polyurethane represents an innovation for the industry, with which the company is helping to promote a more sustainable future.
Each sole production plant produces an average of 20 tons of polyurethane (PU) waste in a year. The RE-YU system enables these materials to be recycled transforming them into a very fine, homogenous powder that is then re-injected into moulds to create new soles.
Stefano Pellizzari, company director, tells us about it.
Dr Pellizzari, what are the most significant innovations of this edition of Simac?
“I am more than satisfied with the performance of the fair this year and pleasantly impressed by the results we achieved. We clearly got the trend of the moment and focused on finding technical and technological solutions to improve productivity, machine efficiency and the quality of our products. In addition, we put special emphasis on the environment and sustainability.
We officially presented an innovative technology called RE-YU, which allows us to recover polyurethane (PU) production waste. A journey that began more than two years ago, during which we analyzed various recycling possibilities, both chemical and physical. Gradually discarding the less promising options, the study led us to identify a physical recycling method that meets our objectives. This process involves grinding production waste and transforming it into a powder to be reused, mixing it with other components and making it injectable once again.”
Why specifically powder?
“We believe that the use of powder is the most advantageous, as confirmed by the data available to us. The use of powder has a lower impact on the final product. It is easy to see that mixing a granule inside a polyurethane foam represents a higher level of discontinuity the greater its size. Furthermore, it should be kept in mind that granules can come from materials of different natures: rubbers, TPU, polyurethane foams, polyester filaments, etc., and that precise separation is almost impossible. These elements behave differently and create different bonds, within the polyurethane foam, that affect the performance of the sole. By minimizing the size of foreign elements, we reduce the effect in terms of “discontinuity,” and at the same time the contact area with the polyurethane foam is increased, reinforcing its inclusion. A good example of this phenomenon is the division of a sphere into many small spheres, which leads to an increase in the total external surface area. This is very intuitive and is confirmed by academic studies.
There are several technologies for reducing material to powder, but they did not meet our needs. The main reason for this was either the cost, as in the case of cryogenic crushing, or the size of the plants, which were too large and not suited to the needs of shoe factories. Our research has led us to develop a plant that is the perfect size for a shoe factory and provides an excellent result with a more economical process. RE-YU is already being tested by some clients because, before it enters the market, we select testers to collaborate with actively, and we have a pilot plant in our factory that operates continuously.”
What feedback did you get during the event?
“Indeed, the feedback we received has been very positive. Visitors to our stand showed a lot of interest in our innovative recycling solution, which is able to reduce the costs and environmental impact of their production processes. The problem for shoe manufacturers is often related to ‘expertise’. There are more effective and efficient chemical recycling processes, but they require specific skills and know-how that are not usually present in these companies. Our physical recycling process is a simple and safe solution that can be used by any shoe factory, regardless of size or expertise. It offers excellent value for money and is in line with our sustainability philosophy. We are convinced that RE-YU is the ideal solution for shoe manufacturers who want to reduce their environmental impact, cut costs and improve the sustainability of their products.”
I am curious to know how your project will evolve. Do you already have ideas in mind?
“Of course, we have thought about it. Our physical recycling system is already applicable to our plants, so it is ready to be used. From here, however, new possibilities for development rightly arise. There are some lines we are pursuing, but we cannot reveal them at the moment. Obviously, our next goal is to increase the amount of waste that we can reuse. This would allow us to further reduce the environmental impact of polyurethane. We are very satisfied with the work we have done. RE-YU has a positive impact both environmentally and economically. This makes it a truly advantageous solution for everyone.”
Wishes for the future?
“We have already achieved what we hoped for: proving that our large-scale tests have confirmed the positive results we had predicted since the development phase. The feedback from our customers is extremely positive, as they consider our solution to be innovative and versatile compared to the alternatives on the market. This response fills us with joy and gives us confidence in the future of RE-YU technology. Despite the fact that we are still at the beginning, we are happy to be at the forefront of an increasingly growing market. We will continue to invest in research and development to further improve our services and meet the complex needs of our customers.”

Stefano Pellizzari and Ettore Bordin, owners of Stemma Srl