The integration of the “by-design” aspects in REDONDO, includes the study and determination of the specification and requirements associated with the development of rPEX and its additives, with the selected end-use applications. The partners that will synthesise rPEX will closely collaborate with SILON and the end-users, KBE and INTER, to determine the requirements in terms of throughput, reaction conditions (chemicals, additives, temperature, time, energy), and synthesis requirements based on the fundamental understanding developed previously by all RTDs. The usage temperature, recycling temperature, recycling conditions and debonding duration will be particularly important. Additionally, the study of properties of current materials as reference material in terms of properties will be included. The results of this work will help set up the material specifications in terms of processes validation requirements for the final assessment.

The integration of safe and sustainable by-design aspects in REDONDO is not limited to rPEX, but it also includes the additives that will be incorporated in rPEX. Depending on the specific applications of a material, it is necessary to incorporate different additives. These can be stabilisers, mineral fillers, lubricants or anti-stick agents.
In REDONDO, the following additives will be used:

• Mineral fillers. Their use contributes to increasing the mechanical properties and the fire resistance of the material.

• Thermal stabilisers. Thermal stabilisation is used as a primary or secondary thermal protection against degradation, which can start during kneading or extrusion process.

• Primary stabilisation is based on a sterically hindered phenolic antioxidant protecting the polymeric against thermo-oxidative degradation. Stabilisation is odourless, stable to light and has excellent colour retention.

• Secondary stabilisation is based on an organophosphite. The stabiliser prevents process-induced degradation and extends the performance of the primary antioxidants.

Additionally, lignin- and cellulose-based nanoadditives will be incorporated in rPEX. The requirements of these novel nanoadditives in terms of properties and processes (throughput, reaction conditions, etc.) will be defined. Since nanomaterials will be used, safety requirements will be investigated as well, and appropriate processes will be implemented in order to ensure the safety of all the production chain and the final products.
All specifications will be determined through a close collaboration of the nanoadditives producers, with the formulator and the end-users.