Thermally and base-triggered ‘debond-on-demand’ crosslinked polyurethane adhesives

Abstract

To address current industrial needs and modern legislation, a series of rapidly degradable and strongly adhering crosslinked polyurethanes featuring the commercially available and degradable chain-extender 2,2’-sulfonyldiethanol have been made for use as depolymerisable coatings and ‘debond-on-demand’ hot-melt adhesives. Variation of the chain-extended polyurethane (CEPU) composition, through increased hard segment content, provided a route to tailor the mechanical, adhesive, and degradable characteristics, whereby CEPUs with ultimate tensile strengths and elongation at break of up to 42.68 MPa and 17.59 e, respectively, could be achieved. The adhesive shear strength of the CEPUs was investigated on a selection of substrates with the highest shear strength observed of 7.80 MPa on aluminium. Depolymerization was triggered via exposure of the CEPUs to tetra-butylammonium fluoride (TBAF), causing the solubilisation of the CEPUs and the generation of low molecular weight species. Rapid ‘debond-on-demand’ adhesion was also achieved upon exposure to 1 M TBAF(aq), with losses in shear strength of up to 34% on aluminum when exposed for 30 minutes.