Recycling of EPDM via Continuous Thermo-Mechanical Devulcanization with Co-Rotating Twin-Screw Extruder

1 Dipartimento di Chimica, Università di Torino, Via P. Giuria 7, 10125 Turin, Italy
2 F.lli Maris S.p.A., Corso Moncenisio 22, 10090 Rosta, Italy

Devulcanization represents the recycling of choice for a homogenous rubber waste stream
because it allows revulcanization of samples previously devulcanized, making the life of the rubber
virtually endless, according to the principles of circular economy. Among the many devulcanization
processes, the thermo-mechanical one is the most appealing because it is a continuous process, easy
to be industrialized. In this paper a comprehensive set of analyses (FTIR, TGA, DSC, elemental
analyses, Py-GC/MS, swelling tests) were carried out on a post-industrial ethylene propylene diene
monomer (EPDM), thermo-mechanical devulcanized in a co-rotating twin-screw extruder with
different process parameters (thermal and screw profile, rpm). Results of the swelling test according
to the Flory–Rehner theory and Horikx analyses show that the higher the thermal profile and the
higher the rpm, the higher is the percentage of devulcanization. The quality of the devulcanized
sample in terms of sol fraction and percentage of random scissions depends on the process conditions.
The screw profile concurs to the efficiency of the devulcanization: the different number of kneading
elements and more in general the screw profile composition affects the percentage of devulcanization,
making the results in some tests more dependent on the screw speed.

https://doi.org/10.3390/polym14224853