Ground tire rubber and coffee silverskin as sustainable fillers in EPDM compounds for rubber‐to‐steel bonded systems in roofing applications

In this paper two waste fillers, namely ground tire rubber (GTR) and coffee silverskin (CSS, a waste bio-product from the coffee-making process), have been used to produce sustainable ethylene-propylene-diene monomer (EPDM) rubber compounds vulcanized on steel sheets to fabricate rubber-to-steel bonded systems for industrial roofing applications. The compounds have shown good mechanical performances, with elastic moduli in the range of 13-16 MPa, tensile strength of 13-20 MPa and elongation at break >400%, and strong adhesion to the metal substrate. Moreover, the rubber-to-steel bonded systems present good sound insulation properties (mean sound transmission loss [STL] of 39 dB and noise level reduction in simulated hailstones impact tests of 62 dB with respect to bare steel 73 dB). Accelerated UV- and thermal-aging tests have shown excellent adhesion of the compounds to the metal substrate with the CSS acting as an antioxidant agent preventing excessive polymer degradation. The selected waste-derived materials result in promising fillers for more sustainable rubber compounds. Highlights Waste fillers were used to produce sustainable rubber compounds. Rubber-to-steel bonded systems for roofing applications were produced. Rubber-to-steel bonded systems have good sound insulation properties. Rubber-to-steel bonded systems have excellent adhesion. Coffee silverskin filler acts as an antioxidant agent.