Alkaline Microenvironments Enable High-Temperature Resistance in Waterborne Silicone Pressure-Sensitive Adhesives

Achieving high-temperature heat resistance in waterborne silicone pressure-sensitive adhesives (SiPSAs) without resorting to complex formulations remains a considerable challenge. This study addresses the issue by introducing a minor quantity of K 2 CO 3 into a straightforward waterborne silicone emulsion. Utilizing cryogenic transmission electron microscopy and tomography, the microphase structure of silicone droplets was visualized, while spectroscopic analyses confirmed chemical changes within the adhesives. A dual-curing mechanism is proposed: the dissolved K 2 CO 3 establishes localized alkaline microenvironments within the silicone droplets, catalyzing a secondary condensation reaction among hydroxyl groups on the polydimethylsiloxane (PDMS), MQ resin and a polyol leveling agent. This process generates additional chemical cross-links concurrently with the conventional free-radical curing initiated by benzoyl peroxide. The resulting network exhibits increased density and thermal stability, enabling the SiPSA to endure temperatures up to 220°C, with a notable improvement of 60°C over the control. This work presents an efficient method for producing high-performance, environmentally friendly SiPSAs and provides insights into the inherent microphase structures of silicone composite droplets, which can benefit future material design. A silicone pressure-sensitive adhesive with outstanding heat-resistance was fabricated from aqueous emulsion, and cryogenic transmission electron microscopy was used to characterize detailed structure of the emulsion droplets.