A fluoride degradable crosslinker for debond-on-demand polyurethane based crosslinked adhesives

The requirement to consider the whole lifecycle of products including disassembly and recycling has resulted in considerable interest in debond-on-demand adhesives. These smart materials undergo controlled loss of adhesive strength when subject to a specific stimulus. This paper reports the design of a crosslinked polyurethane (PU) adhesive which incorporates a fluoride responsive degradable group. The crosslinked PU (CLP) adhesive showed a 28 % increase in adhesive bonding strengths by lap shear testing (14.6 MPa) when compared to structurally analogous linear PU (LPU) adhesive (11.4 MPa). After 3 h in contact with fluoride ions, the CLP exhibited a 55 % loss in adhesive bonding strength (from 14.6 MPa to 6.7 MPa) as a consequence of selective degradation of covalent bonds at the crosslinking sites. This work introduces a new route to dismantle components adhered with the widely used PU adhesives, facilitating recovery of valuable materials, and dramatically reducing waste.