Recycling of resin cured IIR-based ground bladder rubber with the assistance of subcritical fluids

In this work, the devulcanization reaction of isobutylene–isoprene rubber (IIR)-based ground bladder rubber (GBR) in GBR/ethylene–propylene–diene monomer (EPDM) blend was investigated through a co-rotating twin-screw extruder. The influences of subcritical fluids (blank sample, water, ethanol, and n-propanol) and temperatures (160°C, 180°C, and 200°C) were investigated. The results confirmed the effectiveness of subcritical fluids in decreasing the gel content. Moreover, gel permeation chromatography analysis demonstrates that the devulcanizing processes with subcritical fluids are more homogeneous, making the molecular weight of sol detached from the devulcanized blend more uniform. Proton nuclear magnetic resonance spectra confirm that the reactivity of devulcanization of subcritical ethanol was the best. The optimal extrusion temperature for devulcanization is 180°C, at which the mechanical properties of the revulcanized IIR/(devulcanized ground bladder rubber [DGBR]/EPDM) blends achieve the best state. When promoting agent alkylphenol polysulfide (450) works with the assistance of subcritical ethanol at the best reaction condition (180°C, 2.0 MPa, and 500 r min−1), the tensile strength and elongation at break of the revulcanizate retain 94.7% and 110.2% of vulcanized IIR (15.91 MPa, 483.62%), respectively.