Enhanced and Reusable Poly(hydroxy urethane)-Based Low Temperature Hot-Melt Adhesives.

Area of Science:

• Polymer Chemistry
• Materials Science
• Adhesion Science

Background:

• Conventional polyurethanes pose sustainability concerns due to isocyanate use.
• Poly(hydroxy urethane)s (PHUs) offer a sustainable alternative but often lack competitive properties.
• Developing PHUs with enhanced properties, like hot-melt adhesion, is crucial for their wider adoption.

Purpose of the Study:

• To investigate the potential of poly(hydroxy urethane)s (PHUs) as reversible hot-melt adhesives.
• To understand how reagent choice influences PHU properties for adhesion applications.
• To explore methods for enhancing the performance of PHU-based adhesives.

Main Methods:

• Synthesized PHUs using dicyclic carbonates and various diamines (aliphatic, cycloaliphatic, aromatic).
• Evaluated hot-melt adhesion properties, including adhesion at elevated temperatures and cohesiveness.
• Assessed thermoreversibility through rebonding tests and analyzed hydrogen bonding via FTIR and rheology.
• Prepared hybrid PHUs by incorporating epoxy resin as a cross-linker to improve high-temperature performance.

Main Results:

• Judicious selection of reagents minimized detrimental hydrogen bonding, enabling hot-melt adhesion.
• Cycloaliphatic and aromatic diamines yielded materials with desirable hot-melt adhesive properties.
• All PHU compositions demonstrated thermoreversibility with comparable lap-shear strength after rebonding.
• Hybrid PHUs exhibited maintained thermoreversibility alongside improved high-temperature adhesion.

Conclusions:

• PHUs can be engineered as effective reversible hot-melt adhesives through strategic selection of monomers and chain extenders.
• The balance of hard and soft segments, along with chain extender choice, is critical for tuning adhesive properties.
• Hybrid PHUs offer a pathway to enhance service temperature while retaining thermoreversibility, expanding their application potential.