Rubber Recycling: Mending the Interface between Ground Rubber Particles and Virgin Rubber

Area of Science:

• Materials Science
• Polymer Chemistry
• Rubber Recycling

Background:

• Recycled ground rubber particles (GRPs) in virgin rubber blends often lead to poor mechanical properties.
• Poor interfacial bonding and modulus contrast at the GRP-virgin rubber interface contribute to reduced performance.

Purpose of the Study:

• To investigate the interface between ground rubber particles (GRPs) and virgin rubber.
• To identify and mitigate factors causing poor mechanical properties in GRP-vulcanizate blends.
• To improve the adhesion and mechanical integrity of recycled rubber composites.

Main Methods:

• Modeling the interface using laminates of cured and uncured rubber strips.
• Developing a surface-devulcanization method to enhance GRP-virgin rubber molecular contact.
• Analyzing interfacial modulus contrast and its relation to curative diffusion.
• Utilizing piperidine diffusion to modify interfacial properties.

Main Results:

• Modulus contrast across the interface was identified as a key factor in poor mechanical properties, alongside poor bonding.
• Surface-devulcanization successfully improved adhesion energy to the level of cohesion energy.
• Piperidine diffusion from GRPs into virgin rubber reduced modulus contrast by acting as an accelerator, promoting cross-linking within the virgin rubber.
• The mended interface significantly improved tensile strength of GRP-containing vulcanizates, approaching virgin rubber levels.

Conclusions:

• Addressing both interfacial bonding and modulus contrast is crucial for effective GRP reinforcement.
• Surface modification and controlled diffusion (e.g., piperidine) can significantly enhance the performance of recycled rubber composites.
• While tensile strength is improved, extensibility remains a challenge for these modified composites.