Switching Off the Tackiness of a Nanocomposite Adhesive in 30 s via Infrared Sintering

Abstract

Soft adhesives require an optimum balance of viscous and elastic properties. Adhesion is poor when the material is either too solidlike or too liquidlike. The ability to switch tack adhesion off at a desired time has many applications, such as in recycling, disassembly of electronics, and painless removal of wound dressings. Here, we describe a new strategy to switch off the tack adhesion in a model nanocomposite adhesive in which temperature is the trigger. The nanocomposite comprises hard methacrylic nanoparticles blended with a colloidal dispersion of soft copolymer particles. At relatively low volume fractions, the nanoparticles (50 nm diameter) accumulate near the film surface, where they pack around the larger soft particles (270 nm). The viscoelasticity of the nanocomposite is adjusted via the nanoparticle concentration. When the nanocomposite is heated above the glass transition temperature of the nanoparticles (T g = 130 °C), they sinter together to create a rigid network that raises the elastic modulus at room temperature. The tackiness is switched off. Intense infrared radiation is used to heat the nanocomposites, leading to a fast temperature rise. Tack adhesion is switched off within 30 s in optimized compositions. These one-way switchable adhesives have the potential to be patterned through localized heating.

pH-Switchable Stratification of Colloidal Coatings: Surfaces “On Demand”

“…19 A means to adjust stratification without altering the starting composition or the deposition method would offer a huge efficiency gain over conventional fabrication technology. 6,[20][21][22] Our vision in the design of a switchable, stratified coating is to draw upon insights from our earlier work 23 to bring together two different materials technologies: colloidal stratification and pH-responsive particles. Here, we show how the stratification of binary particle blends can be switched off (or on) simply by raising (or lowering) the pH of the initial dispersion.…”

Large-Area Patterning of the Tackiness of a Nanocomposite Adhesive by Sintering of Nanoparticles under IR Radiation

“…just 8% of the initial value, thereby providing a significantly better switch-off than obtained from a similar nanocomposite in recently-published work. 20 Placing an opaque mask in contact with the adhesive during exposure to IR radiation created patterned adhesive regions with a spatial resolution of at least 2 mm.…”

“…Because of the enrichment of hard nanoparticles at the nanocomposite surface, a significant change in tack properties is seen at a considerably lower volume fraction of nanoparticles than is predicted by percolation theory. 20,32 Analysis of the nonlinear viscoelasticity of the bulk material was performed in order to explain the switching mechanism.…”

“…The nanocomposite adhesives were heated under IR radiation as a means to switch off the tack adhesion, via the mechanism reported previously. 20 The probe-tack curves in Figure 1b show that at the concentration of 16 vol. % NPs, there is a complete loss of tack adhesion after IR heating for 30 s. The probe was removed from the surface with no evidence for fibrillation, and the adhesive was not tacky to the touch.…”

Tack energy and switchable adhesion of liquid crystal elastomers

“…The optimal stress-strain behaviour is initially strain softening, to aid crack blunting, and eventually becomes strain hardening to stiffen the fibrils, and increase the force required in the latter The stress-deformation curve measured by a probetack test performed on two materials, P1: Poly(butyl acrylate) copolymer and P2: Poly(butyl acrylate) copolymer with CTA. Probe-tack measurements were performed at constant retraction velocity of 0.1mm s −1 [1].…”