Polyurethane Detachable Lamination Adhesives Containing Alkaline Degradable Aromatic Chain Extender

With increasingly strict requirements for environmental protection, degradable adhesives are urgently required to enable recycling challenge. In this paper, an aromatic chain extender, Fmoc-BHA, which can undergo 1,4-elimination under alkaline conditions, and polyurethane adhesives, which readily decompose after deprotection, are synthesized. The molecular weight of the degradable polyurethane decreased from 6.5 × 10⁴ to 1.1 × 10⁴ g/mol after alkaline treatment. The process and mechanism of degradation was studied by nuclear magnetic resonance, Fourier transform infrared, and gel permeation chromatography. The evolution of bond shear strength under different alkaline conditions was tested; the results showed the practicality of using a degradable polyurethane laminating adhesive to enable film detachment.