Composite polyurethane adhesives that debond-on-demand by hysteresis heating in an oscillating magnetic field

Debond-on-demand adhesives are an emerging industrially important technology, allowing components and materials to be readily separated when required, facilitating recycling. Herein, a composite adhesive has been synthesized that can undergo hysteresis heating to debond-on-demand through direct exposure to an oscillating magnetic field. The adhesive is composed of a polyurethane continuous phase with commercial, unfunctionalized iron oxide particles as the filler (between 1 and 20 wt%). 2 mg of the composite containing 8 wt% iron oxide particles was able to bond various surfaces including glass, wood, aluminium and polyvinyl chloride and support a static load of 100 g. The composites were fabricated by melt processing which resulted in a relatively inhomogeneous dispersion of particles. The values of the Young’s modulus, the ultimate tensile strength, modulus of toughness of the adhesives were comparable to those exhibited by a commercial hot melt adhesive but relatively invariant over the series of composites examined. When subjected to hysteresis heating from an oscillating magnetic field, the rate of temperature increase was dependent on the loading level of Fe3O4. Debonding times decreased from approximately 5 min to less than 30 s exposure to the oscillating magnetic field as the Fe3O4 loading level increased from 1 to 20%. These results will help guide the design of new debond-on-demand polymers that can be addressed through exposure to an oscillating magnetic field