Improving High-Speed Separation of Pressure-Sensitive Adhesives from Silicone Release Coatings by Varying Silica Functionality

Abstract

Abstract Improving the separation efficacy of pressure-sensitive adhesives (PSAs) from their protective poly(dimethylsiloxane) (PDMS) release coatings at high speeds (>100 m/min) is crucial for industrial applications like labeling. In our past work, adding 1 wt % hydrophobic fumed silica to release coatings was found to decrease the force required to separate an acrylic PSA from the release coating at 300 m/min by as much as ∼40%. This simple and low-cost modification technique likely lowers the separation force, and hence the separation energy, by reducing the energy dissipated from the separating materials. However, the mechanism by which energy dissipation is lowered in these systems is still an open question. In this work, fumed silicas with various surface functionalities (methyl, PDMS, hydroxyl) and different specific surface areas (∼20−300 m2/g) were added to release coatings. Across different additive types and loadings (0.1−5 wt %), silica was found to lower the high-speed separation force at 300 m/min by ∼20−55%, with higher effectiveness when well dispersed. Despite using different silicas, the impact of well-dispersed silica on lowering high-speed separation forces was generally similar. These systematic experiments across silica types and concentrations were used to develop a plausible hypothesis that the silica particles act as stress concentrators to localize energy dissipation occurring within the release coating. This behavior may be in contrast with that of neat release coatings in which a larger fraction of the release coating material may contribute to energy dissipation. While multiple mechanisms may contribute to dissipation reduction, calculations of silica size and spacing primarily support the proposed stress-concentration mechanism. Finally, the ability to create efficacious silica-modified release coatings was demonstrated at pilot scale, a promising step towards commercial scale production.