Effect of adhesive thickness on the wettability and deformability of polyacrylic pressure‐sensitive adhesives during probe tack test

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Abstract
Effect of adhesive thickness on the wetting and deformation behaviors during probe tack test of pressure‐sensitive adhesive (PSA) was investigated. For this purpose, cross‐linked poly(n‐butyl acrylate‐acrylic acid) [P(BA‐AA)] and poly(2‐ethylhexyl acrylate‐acrylic acid) [P(2EHA‐AA)] random copolymers with an acrylic acid content of 5 wt % and thicknesses in the range of ∼15–60 μm were used. Tack was measured using the probe tack test and the fracture energy was calculated from the areas under force–displacement curve recorded during debonding process. From contact time dependence of fracture energy, the rising rate of fracture energy with contact time increased with increasing of adhesive thickness and was P(2EHA‐AA) > P(BA‐AA). The fracture energy was P(BA‐AA) > P(2EHA‐AA) at shorter contact time, whereas it reversed at longer contact time. This was caused by two different interfacial adhesions: the physical wetting of PSA molecules to the adherend surface with contact time and the chemical interaction between the acrylic acid units and the adherend surface. From the force–displacement curve measured under the condition of sufficient interfacial adhesion, both maximum force and displacement—namely, the deformability of PSA during debonding process—increased with adhesive thickness. The degree of increase of deformability was P(2EHA‐AA) > P(BA‐AA). The fracture energy was found to depend on the development of interfacial adhesion during contacting process and the deformability of PSA during debonding process. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43639.
Funding Information
  • Fujikura Foundation

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