Multimethod Recyclable Thermoset Polybutadiene Polyurethane–Urea via Reversible Disulfide Bonds

Abstract

The thermoset polyurethane materials are characterized by excellent comprehensive properties. However, the stable cross-linked network structure limits their reprocessability and recyclability. In this study, a thermoset polybutadiene polyurethane–urea material with excellent recyclable and reprocessable properties was prepared. The polyurethane–urea material was prepared by reacting isocyanate-capped polybutadiene prepolymer with curing agent 2,2′-dithiodianiline (DTDA containing dynamic disulfide bonds). The tensile strength and elongation at break of the materials were approximately 21.3 MPa and 604%, respectively. The thermoset pieces underwent a dynamic disulfide exchange reaction in DTDA/toluene solution and rapidly degraded to soluble fragments (a series of aniline-terminated low-molecular-weight materials) after 40 min at 60 °C. When the recycled soluble fragments were reacted with isocyanate compounds, a thermoset material was obtained again. The tensile strength and elongation at break of the material exceeded 98% of the initial values. After the above degradation–recycling process was repeated once more, the mechanical properties of the second recycled material remained unchanged. Additionally, the thermoset pieces were remolded after being hot-pressed at 150 °C for 10 min to produce high-performance materials. This study uses dynamic disulfide bonds to achieve degradation, recovery, and reprocessing utilization of a high-strength thermoset polyurethane–urea material.