Covalent Adaptable Networks from Commodity Polybutadiene and Rubber Waste

Area of Science:

• Polymer Science
• Materials Chemistry
• Sustainable Materials

Background:

• Conventional rubbers, while versatile, pose recycling challenges due to permanent cross-links.
• Covalent adaptable networks (CANs) offer a solution with stimulus-responsive, reversible cross-links for enhanced recyclability.
• Existing CANs often require catalysts, limiting their practical application.

Purpose of the Study:

• To develop a catalyst-free method for creating recyclable polybutadiene-based rubbers using dynamic bonds.
• To investigate the chemical and mechanical recyclability of these novel CANs.
• To explore the incorporation of fillers and upcycling of rubber waste into these adaptable networks.

Main Methods:

• Incorporation of dithioalkylidenes (catalyst-free associative dynamic bonds) into polybutadiene via olefin metathesis.
• Cross-linking of modified polybutadiene with multiarmed thiols to form adaptable networks.
• Chemical and mechanical recycling processes, including filler incorporation and modification of rubber waste.

Main Results:

• The resulting CANs demonstrated significant recyclability, with toughness increasing up to 7-fold over three cycles.
• Incorporation of fillers like carbon fiber and silica yielded reinforced composites, with fillers recoverable through chemical recycling.
• Devulcanized rubber waste was successfully upcycled into mechanically recyclable composites with 90% recycled content.

Conclusions:

• A novel, catalyst-free method for creating recyclable rubbers based on covalent adaptable networks has been established.
• The developed materials exhibit enhanced mechanical properties and toughness through multiple recycling cycles.
• This approach offers a sustainable pathway for upcycling rubber waste into high-value, reusable materials.