Morphology and elasticity of waterborne acrylic pressure-sensitive adhesives investigated with atomic force microscopy

Abstract

The morphology of pressure sensitive adhesives (PSAs), especially at the surface in contact with a release liner, is expected to have a dominant influence on the tack strength and energy in an application. We have used tapping-mode atomic force microscopy to determine the morphology at the surfaces of freshly-cast waterborne acrylic PSAs over lateral length scales of a few µms. We demonstrate that topographical features on silicone release liners can be used to pattern the PSA surface in contact with it. Control of the texture of a PSA surface can potentially be exploited to tailor its properties. Latex particle boundaries are much better defined at the air surface of the PSA in comparison to its back face. A series of experiments suggest that this difference results from the distribution of water-soluble species within the dry film. The pressures and processes involved in the transfer lamination process do not alter the PSA morphology. The first reported AFM images of the response of these materials to pressure and shear provide insight into the deformation mechanisms. Amplitude-distance curves on PSA surfaces show that there is a small decrease in tack and an increase in stiffness after ageing for 13 months.

Characterizing the Distribution of Nonylphenol Ethoxylate Surfactants in Water-Based Pressure-Sensitive Adhesive Films using Atomic-Force and Confocal Raman Microscopy

“…It is consistent with the conclusions from the study conducted by Mallégol et al on the film formation and surface morphology of water-based PSA film. [16][17][18] It is interesting that the surfactant forms a compact, more elastic structure relative to the latex spheres. Varying tapping strength (A/A 0 ) during the imaging also showed significantly greater compressibility of particle domains.…”

“…Fourier transform infrared spectroscopy (FTIR), 6 attenuated total reflec-tion (ATR) FTIR, [6][7][8]15,[19][20][21][22][23] infrared microscopy, 8 X-ray photoelectron spectroscopy, 12 nuclear magnetic resonance, 8,16 and Rutherford backscattering spectroscopy (RBS) 17,24 have been used to collect out-of-plane distribution data of surfactant. However, these techniques either cannot provide layer by layer depth profiling information or only allow for analysis within a few microns of the surface.…”

Skin Development during the Film Formation of Waterborne Acrylic Pressure-Sensitive Adhesives Containing Tackifying Resin

“…This is a surprising result, because the particles in this acrylic latex have been found previously to retain their identity even when heated or subjected to shear stress. [34] A second phase is always observed at the surface of the neat acrylic latex, whereas with the addition of TR, this phase is no longer apparent.…”

“…The distribution and migration of small molecules, especially surfactants, [27,29,31] has also been correlated with poor waterborne adhesive performance. In our previous research, [32,33,34] we have determined the morphology of waterborne PSAs as a first step in improving their performance.…”

Probing particle structure in waterborne pressure-sensitive adhesives with atomic force microscopy

“…More recently, scanning near-field optical microscopy [26] has been applied for these purposes. In our previous research, [27,28,29,30] we determined the morphology of waterborne PSA films using atomic force microscopy (AFM), as a first step in correlation with properties.…”