Degradable, Ultraviolet-Crosslinked Pressure-Sensitive Adhesives Made from Thioester-Functional Acrylate Copolymers

Area of Science:

• Polymer Chemistry
• Materials Science
• Sustainable Chemistry

Background:

• Traditional pressure-sensitive adhesives (PSAs) utilize irreversible crosslinking, creating insoluble networks that hinder recycling of materials like glass and cardboard.
• The presence of these persistent networks complicates waste management and limits the circular economy potential of packaging.

Purpose of the Study:

• To design and synthesize novel degradable PSAs that offer high performance during application.
• To enable efficient network degradation post-use, facilitating easier recycling of PSA-containing products.

Main Methods:

• Radical copolymerization of n-butyl acrylate with a photo-crosslinker (4-acryloyloxy benzophenone, ABP) and a degradable thioester component (dibenzo[c,e]oxepin-5(7H)-thione, DOT).
• Optimization of ABP and DOT molar content to achieve desired tack and peel strengths.
• Evaluation of network degradability via aminolysis and thiolysis, assessing dissolution and loss of adhesive properties.

Main Results:

• Optimal performance was achieved with 0.05 mol% ABP and 0.25 mol% DOT.
• Degradation via aminolysis or thiolysis resulted in complete network dissolution.
• Adhesive films exhibited a significant decrease in tack and peel strengths post-degradation.
• Model labels demonstrated quick detachment from substrates after network degradation.

Conclusions:

• Incorporating dibenzo[c,e]oxepin-5(7H)-thione (DOT) into PSAs creates degradable thioester backbones.
• These degradable PSAs maintain essential adhesive properties during use.
• The developed PSAs offer a promising solution for recyclable packaging labels, addressing current recycling challenges.