Influence of natural aging on the properties of recycled EPDM rubber compounds in different environments

The need to recycle elastomeric waste requires studying its viability in industrial applications. This study investigates the feasibility of recycling elastomeric waste by analyzing whether virgin ethylene-propylene-diene monomer (EPDM) can be replaced by blends of virgin EPDM and thermomechanically and microwave devulcanized EPDM (EPDMd) in industrial applications from the perspective of environmental degradation. Two types of samples were examined: conventional EPDM used to roof membranes, and EPDM blended with different amounts (20, 40, and 50 phr) of EPDMd. Samples were subjected to natural aging in coastal and mountainous environments. Results show that mechanical properties decline with higher EPDMd content and, to a lesser degree, with prolonged outdoor exposure. The coastal climate proved more aggressive than the mountainous one when EPDMd content exceeded 40 phr. Zinc stearate (ZnSt2), a byproduct of vulcanization, was found to influence the evolution of the mechanical behavior. The combined analysis of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), abrasion tests, and thermogravimetric analysis (TGA) provided insights into the degradation processes of these elastomeric blends