Tailoring the Surface Properties of Silicone Elastomers to Improve Adhesion of Epoxy Topcoat

Abstract

Two modification routes have been applied to control the surface properties of spin-coated and screenprinted poly(dimethylsiloxane) (PDMS) layers and to improve their adhesion to a photopatternable epoxy resin topcoat. The first route is based on the optimization of low-pressure oxygen and ammonia plasma treatments to generate acidic or basic reactive surface groups capable of forming covalent bonds with the epoxy groups of the topcoat. The main disadvantage of these fast and practicable processes is the instability of the modification effects. Therefore, the plasma-activated PDMS surfaces were used for subsequent 'grafting to' procedures with reactive polymers. The functional surface groups generated by oxygen or ammonia plasma treatments of PDMS (SiOH, OH, COOH and NH 2 ) were used as anchors to graft epoxy group containing homopolymers and copolymers as well as maleic anhydride copolymers. All of grafted materials provided thin barrier layers that prevented the hydrophobic recovery of the modified PDMS surface. A very promising concept to tailor the surface properties of PDMS is the grafting of epoxy group containing methacrylate copolymers. Depending on the molar ratio of the monomers used the epoxy groups will act mainly as anchor groups. The surface properties of the grafted layer will, then, be controlled by the functionality of the second comonomer.In order to study the effect of the surface modifications on the surface properties of the silicone elastomer layers we used a combination of various surface-sensitive characterization techniques, namely, X-ray photoelectron spectroscopy (XPS), contact angle and electrokinetic measurements as well as roughness analysis. Additionally, pull-off tests were carried out to quantify the effect of the surface modification on the adhesion between an epoxy resin and PDMS.

Influence of roughness and capillary size on the zeta potential values obtained by streaming potential measurements

“…Electrokinetic measurements have been performed for several decades to study surface functionalities, modifications, and interactions of solids. Some recent examples from the authors' group include the characterization of polyelectrolytes, for example, for water purification by flocculation, 2 the proof of polymer surface activation by plasma treatment and polyelectrolyte adsorption to improve adhesion, 3 a study of the influence of fiber surface properties on fiber‐matrix interactions and mechanical properties of cementitious composites, 4,5 the monitoring of surfactant adsorption on photoresist to control capillary forces in photolithography, 6 and the investigation of functional and responsive thin polyelectrolyte layers on flat surfaces 7 and nanoparticles 8 …”

“…Electrokinetic measurements have been performed for several decades to study surface functionalities, modifications, and interactions of solids. Some recent examples from the authors' group include the characterization of polyelectrolytes, for example, for water purification by flocculation, 2 the proof of polymer surface activation by plasma treatment and polyelectrolyte adsorption to improve adhesion, 3 a study of the influence of fiber surface properties on fiber-matrix interactions and mechanical properties of cementitious composites, 4,5 the monitoring of surfactant adsorption on photoresist to control capillary forces in photolithography, 6 and the investigation of functional and responsive thin polyelectrolyte layers on flat surfaces 7 and nanoparticles. 8 Depending on size and shape of the investigated material, various techniques are available: electrophoresis NMR and particle charge detector for molecules and colloids, electrophoresis for diluted nanoparticle dispersions, electroacoustics for more concentrated dispersions, and streaming potential/streaming current measurements for fibers, powders, porous materials, and flat surfaces.…”

Effect of different coupling agents on the interfacial properties of tube–internally insulated foam materials interface in a composite cross‐arm under water environment

“…Meanwhile, as for the foam part, the obvious signal at 922 cm À 1 belonged to the epoxy groups. The foam exhibited absorption bands due to N-H stretching and bending vibrations (ν N-H and δ N-H ) at 3387 cm À 1 and 1604 cm À 1 , respectively [14,15]. It was concluded that these N-H groups might be introduced from the amine curing agent in the cross-linking process.…”