Additive Manufacturing

Background

Plastic materials have become an essential part of everyday life thanks to their low weight, colourability, corrosion resistance and formability. As a result, they are used across a wide range of applications. When elasticity and flexibility are required, vulcanised rubbers are traditionally used. However, rubbers are difficult - or even impossible - to recycle and require specific processing expertise, which limits the number of companies active in this field.

To improve processability and recyclability, thermoplastic elastomers (TPEs) were introduced in the 1960s as an alternative to conventional rubber materials.

Over the past 10 to 15 years, a broad range of new TPE materials has been developed, enabling them to replace rubber in many applications. Despite this progress, knowledge on the recycling of TPEs within the France–Wallonia–Flanders cross‑border region remains relatively limited.

Sustainable recycling

Within the Interreg ElastoPlast project (2016–2021), awareness of TPE materials and their potential was promoted throughout the cross‑border region. Building on this foundation, the Elast2Sustain project focuses on the recycling of end‑of‑life TPE products and the reuse of recycled TPE materials through various processing techniques.

One of the key approaches under investigation is additive manufacturing, commonly known as 3D printing. This research is carried out by the Université de Reims Champagne‑Ardenne (URCA).

Recycled TPE materials

Additive manufacturing enables the production of components - particularly architectural structures - by adding material layer by layer.

By using material only where it is needed, this approach can significantly reduce raw material consumption. Combined with recycling, additive manufacturing also contributes to lowering the overall CO₂ footprint.

Depending on the hardness of the TPE materials, two additive manufacturing routes are considered:

Fused Filament Fabrication (FFF), using filaments produced from harder TPEs
Pellet Additive Manufacturing (PAM), using pellets derived from softer TPEs

From waste to new objects

The transformation of recycled TPE into new printed objects follows a multi‑step process.

First, discarded TPE materials are mechanically ground into smaller flakes.
These flakes are then processed via extrusion to produce filaments, making the material suitable for additive manufacturing.
During the actual additive manufacturing, the filaments are transformed into the desired objects.
The final step enables recycled TPEs to be transformed into high‑value applications.

Printing parameters

Throughout the production of printed parts, various printing parameters are studied to optimizee the structure and mechanical properties. These parameters include:

Printing temperature
Printing speed
Layer thickness
Deposition orientation

The balance between quality and production speed depends on the priority of the intended application.

In some cases, surface finish and mechanical performance are critical, while in others faster production may be prioritized.

Achieving the right compromise often requires fine‑tuning several parameters.

Characterization

To assess the impact of material choice and processing parameters, the final phase of the project focuses on an in‑depth characterization of the printed parts.

These parts will be evaluated in terms of:

Mechanical properties (tensile, flexural, impact and compression, depending on the application)
Thermal behaviour (TGA, DSC)
Structural characteristics (tomography, microscopy, DSC)

This comprehensive characterization will allow us to determine whether recycled TPE materials are suitable for additive manufacturing and to identify the processing conditions under which optimal performance can be achieved.