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Pull-Off of adhesive viscoelastic solids




Duration: NanoX master Internship (8 months part-time in-lab immersion)

Latest starting date: 01/12/2022

Localisation: Nanotech, LPCNO
INSA Toulouse
135 Avenue de Rangueil
31077 Toulouse, Cedex 4

Simon RAFFY, Dr

Work package:
Solid viscoelastic materials are commonly used for adhesion (ex: adhesive tape, reversible sealing for microfluidic [1, 2], etc.). They exhibit simultaneous viscous and elastic characteristics. In the case of solid-viscoelastic rubbers, their solid behavior is a consequence of their crosslinked polymer network which can elastically recover once an applied force is stopped. Furthermore, its liquid behavior is due to a flow between macromolecules and give a viscosity dependent flow rate when stress is applied. It adds a time dependent trend on the stress-strain relationship. If a viscoelastic adhesive material is tearing very fast, it acts as a solid. On the other hand, for low pulling rate, all the viscous components are relaxed. Between those two domains, the response is a combination of the viscous and elastic behaviors. This velocity dependence is not experimentally studied in the literature [3, 4] which results in non-comparable and partial measurements. Exploring the pull-off dynamics of adhesion with a wide range of pulling rates will lead to a new methodology for viscoelastic adhesion measurements. The results obtained in this study will be compared with theoretical models [5] to get an experiment/model convergence. The experiment will be: Casting viscoelastic samples Create and modify measuring program (Labview or python) Measure pull-off forces Adapt the set-up to go near the theorical model Mechanical properties and shape of the adhesive sample Size of the indenter to stay in the working range of the machine

Left : Sample load in the electromechanical set-up. Right : pull-off measurement with the three steps.

1 - Raffy, S.; Palleau, E.; Ressier, L. Reversible Microfluidic Chip. WO 2020084255 A1, 2020 2 - Raffy, S. et al. ACS Appl. Polym. Mater. 2021, 3, 801– 810 3 - Aiva Simaite and Matthew Spenko. 2019 Bioinspir. Biomim. 14 046005 4 - Perrin, H. et al. Soft Matter, 2019,15, 770-778 5 – Müser, H. M. and Persson, Bo N. J. EPL, Volume 137, Number 3, February 2022

Areas of expertise:
Solid mechanics, polymer, adhesion

Required skills for the internship:
Background in materials science with knowledge on polymer’s physic.