Adhesive and mechanical properties of soft nanocomposites: Model studies with blended latex films

Abstract

ABSTRACT:We used a unique approach based on contact mechanics to quantify the adhesive and linear viscoelastic properties of latex films approximately 100 m thick. The latex films were formed from a mixture of two particle types and form stable films consisting of rigid and compliant regions. We used atomic force microscopy to verify that these regions remained well dispersed on the length scale of the original particle size. The properties of the films were determined by h , the volume fraction of the stiffer component. For h Ͻ 0.45, the films were quite adhesive, with viscoelastic properties determined by the compliant matrix material. Adhesive interactions between the film and indenter enabled us to oscillate the indenter in the direction normal to the film surface while maintaining a constant contact area, allowing us to determine the frequency dependence of the dynamic moduli of the films. Stiffer films with higher volume fractions of hard particles were characterized by indentation measurements, from which we were able to determine the time dependence of the relaxation modulus of the latex films. All results were consistent with a power-law form of the relaxation modulus with an exponent of 0.25. The magnitude of the relaxation modulus increased by a factor of 3000 as the volume fraction of hard particles increased from 0 to 0.89. For low values of h , the composition dependence of the film stiffness was similar to the concentration dependence of the viscosity of spherical particle suspensions. A much weaker concentration dependence was observed for the highest values of h , where the properties of the films were dominated by the stiffer component.

Assessing the effect of latex particle size and distribution on the rheological and adhesive properties of model waterborne acrylic pressure-sensitive adhesives films

“…Fabbroni et al [25] studied the adhesive and mechanical properties of hardsoft nanocomposites. The nanocomposites were made from blends of two different latexes, a latex of small particle size (55 nm) and low T g (soft), and another of large particle size (268 nm) and high T g (hard).…”

How latex film formation and adhesion at the nanoscale correlate to performance of pressure sensitive adhesives with cellulose nanocrystals

“…However, while some of these works mention the potential to correlate the nano-adhesion of model PSAs to their 'bulk' tack, and peel and shear strengths, no direct comparisons to these specific metrics have been made [59][60][61]. In fact, most other nano-adhesion studies of PSAs also focus solely on their properties at the nanoscale [38,62,63] or compare them to other bulk properties such as the rheological behaviour of the latex [64]. Furthermore, Phillips et al [61] reported the only other account where, to our knowledge, nanoparticle reinforced latexes were investigated using nano-adhesion measurements.…”

Bulk and Interfacial Contributions to the Adhesion of Acrylic Emulsion-Based Pressure-Sensitive Adhesives

“…Small-Strain Oscillatory Test. The linear viscoelastic properties of the adhesive layer were obtained by applying a sinusoidal displacement to the adhesive layer and measuring the resultant load: 11,12,32 t sin( )…”