A Calorimetric Evaluation of Peel Adhesion

Peeling of flexible poly(ethylene terephthalate), PET, and elastic steel films, adhesively bonded with a pressure sensitive adhesive layer, was analyzed from a thermodynamic perspective with the intent of determining how the energy expended in separating the bonded materials is consumed. The mechanical work expended and the heat dissipated during peeling were simultaneously measured using deformation calorimetry. For the PET backing material, which has a demonstrated capacity to store deformation energy as latent internal energy, most, but not all, of the peel energy was dissipated as heat. When perfectly elastic steel films were peeled, all of the peel energy was dissipated as heat, proving that no latent internal energy is stored in the adhesive layer during peeling and suggesting that the internal energy change of peeling adhesive backed with PET film was stored as latent internal energy in the PET backing. The stored latent internal energy in the peeled PET was measured using solution calorimetry. The thermodynamics of tensile drawing for PET was studied using deformation calorimetry, solution calorimetry, differential scanning calorimetry and thermomechanical analysis.