Development of Bio-Based and Recyclable Epoxy Adhesives by Modification with Thermoplastic Polymers

Area of Science:

• Materials Science
• Polymer Chemistry
• Adhesive Technology

Background:

• Development of sustainable and high-performance adhesives is crucial for reducing environmental impact in structural applications.
• Bio-based and recyclable epoxy resins offer a promising alternative to traditional petroleum-based adhesives.
• Incorporating thermoplastic polymers can enhance adhesive properties and enable recyclability.

Purpose of the Study:

• To design novel epoxy adhesives by incorporating polyetherimide (PEI) and poly(ε-caprolactone) (PCL) into a bio-based epoxy resin.
• To evaluate the mechanical, rheological, thermal, and adhesion properties of the modified adhesives at various temperatures.
• To assess the recyclability and potential for joint disassembly of the developed epoxy adhesives.

Main Methods:

• Synthesis of epoxy adhesives by blending PEI and PCL with a bio-based epoxy resin (Polar Bear).
• Characterization of mechanical properties (quasi-static and dynamic), rheology, thermal stability, and adhesion in single-lap joints.
• Testing adhesion performance at -55 °C, 23 °C, and 80 °C.
• Evaluation of recyclability via an acid-based process.

Main Results:

• Low PEI content (≤3 wt%) significantly improved mechanical performance and toughness while maintaining processability.
• Exceeding 3 wt% PEI content negatively impacted mechanical resistance and workability.
• PCL addition increased viscosity but reduced mechanical performance, though it offers eco-friendliness.
• All modified adhesives outperformed the commercial DP-460 epoxy adhesive in lap shear tests across all temperatures.
• Both PEI- and PCL-modified adhesives demonstrated recyclability through a simple acid-based process.

Conclusions:

• Modified epoxy adhesives with PEI and PCL offer a high-performance, eco-friendly alternative for structural bonding.
• The developed adhesives exhibit excellent mechanical properties, thermal stability, and adhesion, even at extreme temperatures.
• The recyclability of these adhesives supports sustainable practices and circular economy principles in material applications.