Monomaterial Instead of Material Mix: How the "Monomaterial Kit" Rethinks Circular Product Design

Why are many durable plastic products today hardly recyclable – even though they are technically sophisticated? The answer often lies inside the products themselves. Different types of plastics, bonded or firmly joined together, ensure stability or lightweight construction. Yet what performs well functionally becomes a problem in the circular economy. This is where the Fraunhofer Cluster Circular Plastics Economy CCPE comes in with its "Monomaterial Kit".

Multi-material systems have become standard in many sectors – whether in mobility, furniture or technical consumer goods. Different polymers are combined to generate specific properties such as impact resistance, stiffness or insulation performance.

However, this creates a structural problem for the circular economy: different types of plastics are difficult to separate in a pure form. Adhesives or permanent bonds prevent clean material flows. High-quality recycling is therefore considerably hampered – often leaving only downcycling as an option.

The central insight is therefore: material purity is the prerequisite for high-quality circular systems – and it begins in the design phase.

Multi-material systems enable highly specialised property profiles that have been optimised over decades in many applications. The monomaterial approach does not fundamentally question this logic – but it shifts the priority: from maximising material combinations to maximising circularity.

The "Monomaterial Kit" developed by Fraunhofer CCPE is aimed at designers and developers who want to consistently integrate Design for Recycling. The basic principle is both simple and demanding: a single thermoplastic is used within a product in different structural forms.

The same material can appear, for example, as:

• fibre or textile structure
• foam
• self-reinforced sheet
• injection-moulded component

This approach has so far been tested with PET, PLA and PA. The desired product properties are achieved not by changing materials, but by specifically varying the morphology.

The "Monomaterial Design Set" demonstrates how different manufacturing technologies – such as thermoforming, injection moulding or sandwich structures – can be combined within a monomaterial concept. This makes it possible to realise both simple sheets and complex 3D components.

The idea behind it: performance is created through structure – not through material diversity.

The Monomaterial Kit is more than a material concept. It integrates additional aspects that are crucial for the circular economy:

• avoidance of adhesives
• development of recyclable colour pigments
• recycling-compatible flame retardants
• adaptation to regional recycling infrastructures

Within the cluster, specific demonstrators have already been developed, including a "circular child seat" and an insulating reusable transport box. Both examples illustrate that complex and safety-relevant products can also be realised using a monomaterial approach.

The concept can be transferred across industries – particularly for:

• mobility applications
• durable consumer goods
• logistics solutions
• furniture and interior applications

A current practical example is the scientific support of the "Re:think Design Competition" organised by Nowy Styl DACH. Designers are developing recyclable soft-seating furniture based on the Monomaterial Kit. The winners will be announced in April 2026. Circular Design is therefore not only being discussed, but actively tested in practice.

Circular plastic products are not created through subsequent recycling optimisation, but through consistent material and design decisions at the beginning of product development.

This change in perspective is becoming increasingly important right now: rising recycling rates, stricter recycling requirements and growing expectations along the value chain are increasing the pressure to act. Products that are not designed to be recyclable today could lose their competitiveness tomorrow.

The Fraunhofer CCPE's monomaterial construction kit shows that circular design is not a sacrifice, but a systemic approach to innovation: one material, diverse morphologies, combinable manufacturing technologies – and a clear focus on recyclability.