Nicolas Amouroux

Modulation of Adhesion at Acrylic Adhesive-Silicone Elastomer Interfaces

We have recently reported a systematic investigation of the role of MQ resins (small silica-like nanoparticles) in the modulation of adhesion at silicone elastomer lens—nanometric thin acrylic surface anchored layer deposited on a silicon wafer through loading and unloading JKR experiments. This particular system was chosen as it allowed one to vary the MQ resin content in the elastomer, and to test its resulting effect on both the thermodynamic work of adhesion and the adhesive strength at elastomer—acrylic layer interfaces, avoiding any complication due to bulk mechanical properties of a relatively thick (in the micron range) acrylic layer. We present here a complementary investigation, aimed at understanding the role of the resins in the development of specific interactions at the interface. To do so the adhesive energy between silicone elastomers containing various amounts of MQ resins and model substrates made of self-assemble monolayers of thiol molecules with various amounts of carboxylic terminations have been measured through JKR tests. We show that the level adhesion at these interfaces results from a competition between increased interactions and decreased mobility associated with the incorporation of the resins inside the elastomer.

External calibration in PA12 tube extrusion - Part II: Relations between molecular orientation, tensile properties and polymer drawing during calibration

Abstract Elongation at break is one of the major end-use properties of polyamide 12 extruded tubes. It is strongly affected by the tube microstructure and the molecular orientation resulting from extrusion conditions. Molecular orientation was characterized by X-ray diffraction and birefringence evaluation in light microscopy. Measurements were carried out on (r, z) sections obtained by polishing and microtoming. On the other hand, polymer drawing was measured on line by tracer techniques. Calibration stage was determined as the key step of the process that generates orientation in tubes: as the tube is drawn through a cylindrical calibrator under vacuum and cooled from its outside surface, calibration leads to a highly oriented zone in the twenty external microns. Calibration conditions and elongation at break have been connected through orientation level in this region. Molecular orientation was found to strongly depend on the draw ratio in the calibration tank. Finally, birefringence of the tube external layers and elongation at break were successfully correlated. Elongation at break can be enhanced by reducing orientation resulting from calibration conditions.

Adhesion at Poly(Butylacrylate)–Poly(Dimethylsiloxane) Interfaces

We present an investigation of the adhesion modulation mechanisms of silica-like nanoparticles (MQ resins) incorporated in polydimethylsiloxane (PDMS) elastomers and acrylic adhesives. The Johnson-Kendall-Roberts (JKR) test has been used to gain information on the both zero velocity and the velocity dependence of the adhesive strength, avoiding as much as possible contributions to the adhesive strength of bulk dissipation in the adhesive (which is not the case with peel tests). As the incorporation of the MQ resins into the elastomers deeply affects their own mechanical properties, the loading and unloading curves of small poly(butylacrylate) (PBA) lenses on either PDMS elastomers, adsorbed PDMS and pure MQ resin layers are compared in a systematic manner. The PBA chains are observed to have a neat affinity for the MQ resin nanoparticles. When MQ resins are present at the interface, they tend to prevent facture propagation, thus producing a larger deformation of the PBA lens. The modulation of adhesion is then dominated by the corresponding dissipation inside the acrylic adhesive.