Sustainable Structural Hot-Melt Adhesives Enabled by Functionalized Crystalline Lamellae

Area of Science:

• Materials Science
• Polymer Chemistry
• Sustainable Chemistry

Background:

• Conventional hot-melt adhesives (HMAs) exhibit limitations in shear strength and recyclability, restricting their use in structural applications.
• There is a growing need for high-performance adhesives that are also environmentally sustainable and recyclable.

Purpose of the Study:

• To develop a sustainable HMA system from renewable building blocks.
• To achieve a balance between cohesive and adhesive forces for enhanced performance.
• To ensure closed-loop chemical recyclability of the developed HMA.

Main Methods:

• Incorporation of polar functional groups into crystalline lamellae of sulfur-based polymers.
• Evaluation of shear strength on wood and stainless steel substrates.
• Assessment of oxygen and water vapor barrier properties.
• Depolymerization of the HMA system via mild hydrogenation to regenerate monomers.

Main Results:

• The developed HMA system demonstrates high shear strengths: >14.7 MPa on wood and >15.1 MPa on stainless steel.
• The material exhibits excellent oxygen and water vapor barrier properties, suitable for microelectronic encapsulation.
• Complete depolymerization and monomer regeneration were achieved from a mixed materials system under mild hydrogenation.

Conclusions:

• A novel design strategy for structural HMAs has been established, unifying high performance, sustainability, and recyclability.
• The sulfur-based polymers offer a promising alternative to conventional HMAs for demanding applications.
• This work paves the way for advanced, eco-friendly adhesive solutions.