Interfacial and Bulk Contributions to Peeling Energy |
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Authors: | I Kamyab E H Andrews |
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Affiliation: |
a Department of Mechanical Engineering, Imperial College of Science, Technology and Medicine, London, UK
b Department of Materials, Queen Mary and Westfield College, London, UK |
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Abstract: | Thin polyurethane films, having low adhesion to dried protein, were developed as candidate materials for non-adhesive surgical dressings. In order to model wound-adhesion, gelatine was cast from solution on to the film and allowed to dry. The film was peeled from the gelatine at 180° peel angle, and the peel force measured as a function of the temperature of test. The dynamic mechanical properties of the films were measured over the range -90°C to 110°C and values of tan δ were determined at the temperatures employed for peeling. Thus, a correlation was obtained between peeling energy and tan δ for each of eight films.
The generalised theory of fracture mechanics states that the adhesive failure energy is given by the product of an interfacial energy term and a “loss function” involving the hysteresis ratio of the material. If the strains are small the hysteresis ratio is proportional to tan δ. The experimental results show excellent agreement with the theory, but the interfacial term turns out to be much greater than the true interfacial energy (or thermo-dynamic work of adhesion). The reason for this result is discussed. |
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Keywords: | Model for wound-adhesion model non-adhesive surgical dressing peeling energy dynamic mechanical properties polyurethane films fracture mechanics interfacial energy bulk energy dissipation work of adhesion dried gelatine molecular recoil mechanism |
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